Open Access Repository of Indian Theses

Gadi, Ranjith Kumar

Synopsis 
 
 v 
 
The thesis entitled “Electrophile Intiated Reactivity of Functional Alkynes Involving Azide 
as Amine Surrogate for  Medicinally Important Scaffolds” is divided into four chapters. 
Chapter 1: An Overview on Azide as Nitrogen Surrogate 
The development of versatile methodologies to employ azides as aminating agents for the formation of 
nitrogen-containing compounds has attracted significant attention in synthetic chemistry. This review 
examines recent developments in the tandem reaction of azides with alkynes and alkynols. The formation 
of diverse nitrogen containing compounds is classified in this review according to the types of reactions. 
Nitrogen-containing compounds, such as nitriles, azoles,amides, isoquinolines, quinolines, pyridines, 
pyrroles etc., are important scaffolds found in numerous natural products, biologically and 
pharmaceutically active compounds as well as functional materials. These compounds have been 
extensively studied for their biological and therapeutic activities. In addition,  intramolecular processes in 
this area could be powerful strategies for the synthesis of important heterocyclic compounds. With 
continuous research in the tandem reaction of azides with alkynes and alkynols, novel reactions and new 
approaches can be anticipated to appear in the future and be applied extensively in practical synthesis. 
Chapter 2A: Synthesis of Benzofuranyl and Indolyl Methyl Azides by Tandem 
Silver-Catalysed Cyclization and Azidation 
Ag(I)-catalyzed synthesis of 2-azidomethyl benzofurans/indoles from linear and readily available 
hydroxyl /amino-phenyl propargyl alcohols is describedvia a highly regioselectiveC-O and C-N bond 
formations. Control experiments reveal that the reaction involves the sequential Ag(I)-catalyzed5-exo-dig 
Scheme 1:  
 
cyclization and a catalyst free γ-allylic azidation. The synthetic utility of this method has been 
demonstrated by using azidomethyl unit of the above synthesized heterocycles as base for variety of other 
functionalizations, like triazole-, tetrazole-, amide-, amine-, pyrido-derivatives.  
Synopsis 
 
 vi 
 
Scheme 2: Synthetic application 
 
Conclusion: 
In summary, an efficient synthetic route to 2-azidomethyl benzoheteroles based on tandem Ag(I)-
catalyzed intramolecular cyclization and aromatization driven γ-azidation from readily available linear 
propargyl alcohols is reported. While it did not require exclusion of air or moisture, the reaction was 
applicable over a wide range of substrates. The synthetic utility of the reaction was demonstrated by the 
 conversion of azido methyl unit to various other useful functionalities via reduction, oxidation and 
cyclization reactions. 
 
 
Synopsis 
 
 vii 
 
Chapter 2B: In vitro Antitubercular Activity of a Series of Benzofuran And Indole 
Derivatives  
Phosphorylation and dephosphorylation are the key mechanisms for mycobacterial physiology and play 
critical roles in mycobacterial survival and in its pathogenesis. Mycobacteria evade host immune 
mechanism by inhibiting phagosome – lysosome fusion in which mycobacterial protein tyrosine 
phosphatase A (TP) plays an indispensable role. Tyrosine kinase (TK) activated by autophosphorylation; 
phosphorylates TP, which subsequently leads to increase in its phosphatase activity. The activated TP 
after getting phosphorylated is secreted in phagosome of macrophage. In present study we have shown 
that the phosphorylation at two sites of TP; Y128 and Y129 are critical for TK mediated phosphatase 
activity. The disruption of this interaction between TK and TP inhibits activation of later which further 
leads to the decrease in intracellular survival of mycobacteria. Further, the proof of concept has been 
established using Benzyl benzofurans and Benzofuranamides which inhibit the growth and intracellular 
survival of mycobacteria, associate with the functional sites of TP and contend with the TK. 
Table 1.  Screening  series of compounds against PtpA 
Sl. no. Compound  %Inhibition at 25 
µM 
MIC 
(µM) 
CC50 
1 S015-2211 64 50 ≤100 
2 S015-2212 96 > 50 >100 
3 S015-2213 76 > 50 >100 
4 S015-2214 74 > 50 >100 
5 S015-2215 68 > 50 ≤100 
6 S015-2216 1 > 50 >100 
7 S015-2217 65 50 ≤100 
8 S015-2218 63 > 50 ≤100 
9 S015-2219 47 > 50 >100 
10 S015-2220 58 > 50 >100 
11 S015-2221 51 50 ≤100 
12 S015-2222 71 50 >100 
13 S015-2223 6 50 ≤100 
14 S015-2224 100 50 >100 
15 S015-2225 50 50 ≤100 
Synopsis 
 
 viii 
 
16 S015-2226 46 > 50 >100 
17 S015-2227 22 > 50 >100 
18 S015-2228 74 > 50 >100 
19 S015-2229 62 > 50 >100 
20 S015-2230 57 > 50 ≤100 
21 S015-2231 88 > 50 >100 
22 S015-2232 44 > 50 >100 
 
In conclusion these compounds were evaluated for their roles in intracellular survival of Mtb infected 
macrophage cell line. Both these inhibitors disrupt the TK-TP interaction  in vitro, and S015-2224 proved 
to reduce the Mtb survival up to 50 percent at 3.12μM to 25μM concentration. 
Chapter 3: A Direct Access to Isoxazoles from Ynones using Trimethylsilyl Azide as Amino 
Surrogate under Metal/Catalyst free Conditions 
In this chapter, A general method for isoxazoles from readily available ynones using trimethylsilyl azide 
as amino surrogate, likely via an unprecedented hydroazidation of alkyne and denitrogenative cyclization, 
is demonstrated. The method neither required any catalyst nor demanded the unusual conditions to afford 
the products with outstanding functional group compatibility. we herein presented a direct access to 
isoxazoles from ynones using TMSN3 as amino surrogate. This new method is step economical and it 
does not require (1) assistance of any metal/catalyst, (2) harsh reaction conditions, and (3) exclusion of air 
or moisture. 
Scheme 3: Synthesis of isoxazoles  
 
Conclusion: 
In this chapter we have illustrated a highly general and straightforward method for the synthesis of 
isoxazoles from readily available ynones using TMSN3 as amino surrogate. The reaction likely proceeds 
via tandem azidation and denitrogenative cyclization (providing a new set of disconnections), offering a 
single pot C-N and O-N bond formation. Further, a high reaction scope with respect to both terminals of 
Synopsis 
 
 ix 
 
ynone together with excellent product yields makes it a practical approach for the highly privileged 
scaffold. 
Chapter 4: A Nickel-Catalyzed anti-Carbometallative Cyclization of Alkyne-Azides With 
Organoboronic Acids: Synthesis of 2,3-Diarylquinolines 
An anti-carbonickelative cyclization via reversible alkenylnickel E/Z isomerization of 2-azido phenyl 
propargyl alcohols with aryl boronic acids is achieved using Ni(acac)2 as the catalyst to access 2,3-diaryl 
quinolines. It represents a rare example of trapping the vinyl metal intermediate with a nitrogen center, a 
non-carbon center electrophile. 
Scheme 4: Synthesis of 2,3-Diarylquinolines 
 
 
Conclusion: 
azidophenyl propargyl alcohols could be cyclized to 2,3-diaryl quinolines via arylation with aryl boronic 
acids under Ni(II)- catalysis. Selective carbonickelation, E/Z isomerization of the nickel intermediate and 
capture of the C-M centre by an internal azide as a rare non-carbon electrophile were highlights of the 
redox-free catalytic process. A thorough verification of substrate scope with respect to both boronic acids 
and the alkyne-azides was done to prove the practicality of the method. 
 
 


English

Electrophile Initiated Reactivity of Functional Alkynes Involving Azide as Amine Surrogate for Medicinally Important Scaffolds

MARAPAKA, ANIL KUMAR

 Synopsis 
 
xi 
 
SYNOPSIS 
Understanding the structural differences among M1-class 
aminopeptidases and development of novel inhibitors 
Introduction 
Proteins or enzymes are important biological machinery essential for the normal and 
healthy growth of every living cell. In vivo, every protein or enzyme has its specific 
function. Once the biological role of a particular enzyme is fulfilled, it undergoes 
proteolytic degradation and forms individual amino acids. These free amino acids are 
again recycled into a functional protein whenever required. In nature, different 
kingdoms of life have their own proteolytic machinery for protein degradation. But 
unique machinery is present among all kingdoms of life in the form of endopeptidases 
and exopeptidases which are essential in the final stages of the protein degradation 
pathway. 
 Aminopeptidases catalyze the hydrolysis of amino acids from the amino 
terminus of the small peptides. M1 family aminopeptidases play important role in the 
pathogenicity of bacteria and shown to be critical in many physiological processes such 
as regulation of peptide hormone levels, protein maturation, cell cycle regulation, 
memory, antigen presentation, and angiogenesis in humans. They are mono zinc-
containing enzymes which are involved in the release of free amino acids from smaller 
peptides. Except for viruses these enzymes are present in all kingdoms of life. To date, 
there are twelve members of the M1 class represent in humans. Some of them are 
membrane-bound and others are found in the cytosol. Most of the M1 class 
aminopeptidases are reported to be drug targets in various diseases in addition to having 
aminopeptidase activity. Due to the essential roles played by these enzymes, much 
emphasis was given to their biochemical and structural characterization. In addition, 
M1 class proteases from the archaea and bacterial origin are also structurally 
characterized. These are F3 from Thermoplasma acidophilum, aminopeptidase N from 
Neisseria Meningitides (NmAPN), aminopeptidase N from Plasmodium falciparum 
(PfA-M1), and aminopeptidase N from Escherichia coli (ePepN). 
All the M1 class proteases exist as multi-domain proteins. Domains arrangement 
around the catalytic domain, zinc-binding motif (HEXXH motif), and exopeptidase 
motif (GXMEN motif) are conserved among M1 class proteases. All the members of 
 Synopsis 
 
xii 
 
this family have the same catalytic principles. They all have unique amino terminus 
recognition pattern where the carboxy terminus of three glutamates co-ordinates with 
the zinc. Specificity was derived due to the natural variation in residues around the 
substrate-binding pocket or S1 pocket. All the M1 class proteases consist of an 
archetypical S1 pocket including ePepN. In the present study, ePepN has been used as 
a prototype in understanding the biochemical properties and structural basis of M1-
class aminopeptidases. In this protein, the exopeptidase motif (GXMEN motif) was 
preceded by methionine (M260) which acts as a gatekeeper in the S1 pocket and 
accommodates the peptides with a diverse range of residues at the P1 position. 
 The work executed in this thesis entitled “Understanding the structural 
differences among M1-class aminopeptidases and development of novel inhibitors” 
was undertaken with an aim of understanding the role of specific residues on the activity, 
stability, substrate specificity, and protein-ligand interactions of M1 class proteases. In 
this study, we worked on two proteases from this family namely, aminopeptidase A 
from Legionella pneumophila (LePepA) and aminopeptidase N from Plasmodium 
falciparum (PfA-M1). We carried out site-directed mutagenesis on specific residues of 
LePepA and different mutants were generated (LePepA-K132E, LePepA-K132L, and 
LePepA-S276M). Their biochemical properties, kinetic parameters were determined 
and the structural basis was provided for the unique substrate specificity of LePepA. In 
this study, we also have designed a library of hydroxamic acid-based leucine ureido 
derivatives to discover molecules that can specifically inhibit PfA-M1 with a novel 
mode of binding. By analyzing the structural data obtained from different PfA-M1-
inhibitor complexes, we synthesized an inhibitor molecule that has a high degree of 
selectivity towards PfA-M1 over its mammalian counterpart porcine aminopeptidase N 
(PmAPN).  
 This thesis has been divided into four chapters. Chapter 1 discusses the 
introduction, conservation pattern, biochemical, structural information, and 
pathophysiological roles of different M1 class proteases from humans. It provides the 
information about the S1 pocket of M1 class aminopeptidases. Chapter 2 describes the 
materials and methods employed to execute this work. Chapter 3 and chapter 4, each 
chapter is subdivided into three sections. Section 1 is an introduction, section 2 results 
and discussion, and section 3 is the conclusion. Chapter 3 discusses “Discovery, 
 Synopsis 
 
 xiii 
 
biochemical, mechanistic and structural studies of a unique Glu/Asp specific M1 class 
aminopeptidase from Legionella pneumophila”. Chapter 4 deals with “Design and 
synthesis of PfA-M1 selective inhibitors over mammalian counterpart as an 
antimalarial agent and structural evaluation”. 
 
Statement of problem 
Most of the M1 family aminopeptidases studied till date are displayed broad substrate 
specificity, mostly specific to hydrophobic and basic residues. This is explained by the 
presence of hydrophobic S1 pocket in the active site of ePepN along with polar residues 
at the rooftop of the active site. Methionine at gatekeeper position (M260) followed by 
methionine in the exopeptidase motif (GXM263EN) contributes to the hydrophobicity 
of the S1 pocket in ePepN. In the case of human aminopeptidase A (hAPA) with 
additional substrate specificity towards acidic residues, a polar residue (T356) occupied 
the gatekeeper position and diluted the hydrophobicity of the S1 pocket. From this 
observation, we anticipated that if there could be a member from the M1 class 
aminopeptidase that has both the methionine residues, one at gatekeeper position 
(M260) and the other in the exopeptidase motif (M263) are substituted by polar residues, 
and may have higher substrate specificity towards acidic residues. To find out the M1-
class aminopeptidase with two polar residues at both gatekeeper and exopeptidase 
methionine positions, we performed an unbiased search, by providing query sequence 
“X-G-X-X-E-X (2,100)-H-E-X (2)-H-X (18)-E” ( Where X represents variable amino 
acid) which includes signature motifs (exopeptidase motif and zinc-binding motif) of 
M1 class against the PROSITE database using the ScanProsite tool. 100 sequences were 
identified out of ~10,000 hits to have polar residues (Z-G-X-Z-E-X, Where Z represents 
the polar residue) at both the methionine positions. 25 of these 100 sequences consists 
of serine at both gatekeeper (S273) and exopeptidase (GAS276EP) positions. 
Interestingly we found that all these 25 sequences belonged to only Legionella species. 
 In this study, to meet the first objective, we focused on the biochemical and 
structural properties of aminopeptidase A from the extensively studied pathogen 
Legionella pneumophila (LePepA). In this protein, the gatekeeper residue (S273) and 
the residue in the exopeptidase motif (GAS276EP) are polar and the rooftop of the 
active site is occupied by positively charged (K132 and R375) residues in contrast to 
 Synopsis 
 
xiv 
 
hydrophobic residues at gatekeeper position (M260) and exopeptidase motif 
(GAM263EN) and polar but not charged residues at the rooftop of ePepN active site. 
Due to the increased polarity of the wall of the cylinder and positively charged rooftop 
of the S1 pocket, we speculated that LePepA would have different substrate specificity, 
preferably toward acidic residues in contrast to basic and hydrophobic residues in the 
ePepN. LePepA may have evolved to fulfill the specific functions in Legionella species. 
Recently published report on crystal structure of hAPA revealed that a polar residue 
(T356) at the gatekeeper position is involved in stabilization of the substrate with 
glutamate at P1 position by hydrogen bonds and also positively charged residue (R887) 
at the rooftop of the active site forms a salt bridge with the glutamate at P1 position. 
These observations strongly support our reasoning of unique specificity of LePepA 
towards only acidic residues. To confirm our predictions and for further studies we have 
cloned this protein, purified, and crystallized. 
 The second objective of this study is to develop selective inhibitors against 
PfA-M1. Plasmodium parasites causing malaria has developed resistance to most of the 
antimalarials in use, including the artemisinin-based combinations, which are the last 
line of defense against malaria. This necessitates for the discovery of new targets and 
the development of new antimalarials. Aminopeptidase N from Plasmodium falciparum 
(PfA-M1), an M1 class aminopeptidase, is essential for the asexual erythrocytic stage 
of development. This enzyme has been validated as a potential antimalarial drug target. 
Herein we describe the design, synthesis, in vitro and cell based evaluation of a library 
of compounds with leucine hydroxamic acid attached to urea-substituted groups. The 
design is to extend the binding of molecules beyond S2’ pocket of the enzyme to achieve 
the much-needed specificity. Most of the 40 compounds described in this study 
displayed inhibition at sub-micromolar range against the recombinant PfA-M1 with 
negligible cytotoxicity on human cell lines and strong inhibition of the malarial parasite 
growth. However, the selectivity index between the malarial and mammalian M1 
aminopeptidases for all these compounds is very less except for compound 39, which 
has an inclination towards parasite enzyme, by more than 700 fold. Crystal structures 
of PfA-M1 at atomic resolution in complex with at least nine different compounds 
including compound 39 establish the structural basis for the observed inhibition. 
Binding of molecule 39 extends beyond the S2’ pocket where differences between the 
 Synopsis 
 
 xv 
 
malarial and mammalian enzymes are apparent. Together, our data provide important 
insights for the rational and structure-based design of potent and selective inhibitors of 
PfA-M1 that will likely lead to novel chemotherapeutics for the treatment of malaria. 
 
Objectives 
1. Discovery, biochemical, mechanistic and structural studies of a unique Glu/Asp 
specific M1 class aminopeptidase from Legionella pneumophila. 
2. Design and synthesis of PfA-M1 selective inhibitors over mammalian counterpart as 
an antimalarial agent and structural evaluation. 
 
Methodologies used and sample results: 
Discovery, biochemical, mechanistic and structural studies of a unique Glu/Asp 
specific M1 class aminopeptidase from Legionella pneumophila (LePepA) 
 
Activity and substrate specificity of LePepA: 
The full-length gene of aminopeptidase A from Legionella pneumophila (LePepA) was 
cloned, expressed and purified to homogeneity (900 amino acids protein). Activity 
assays were performed with 15 aminoacyl-pNAs and 4 aminoacyl-AMCs as substrates 
against the purified enzyme. Interestingly LePepA preferred only acidic residues as we 
predicted from our earlier bioinformatics studies. 
 
Figure. Enzymatic activity of LePepA with different substrates. 
The activity of LePepA against the Glu-pNA was set to 100 % and compared relative activities 
of other substrates. Results presented are the means ± standard deviation of three independent 
measurements. 
 Synopsis 
 
xvi 
 
Residues in the S1 pocket and rooftop regions are critical for unique specificity toward acidic 
residues:  
 
To provide the structural basis for the biochemical properties of the LePepA, we have 
crystallized the enzyme and solved the crystal structures in the apo form and in complex 
with glutamate and aspartate. The overall structure of the LePepA is folded into four-
domains with thermolysin like catalytic domain. Similar to ePepN structure, LePepA 
adopted the closed conformation. A single zinc ion is observed in the active site of the 
apo structure with conserved H310EFFHX(18)E333 zinc-binding motif. Strong 
electron density was observed for E311 and Y383 which are critical for peptide 
hydrolysis. E311 activates nucleophilic water and Y383 stabilizes oxyanion that results 
from the nucleophilic addition of water on the peptide bond. Representation of S1 
pocket as a cylinder could be reconstructed for the LePepA. Two serine residues present 
in the S273GAS276EP motif are locked by a weak hydrogen bond (3.8 Å). K132 and 
R375 occupied in the rooftop of the S1 pocket and positioned to interact with the 
incoming glutamate or aspartate containing substrates. K132 involved in hydrogen 
bonding with the main chain carbonyl of the E134 (2.6 Å) and S276 (3.1 Å). Similar to 
ePepN, three glutamates (E134, E277, and E333) involved in the formation of an anion 
hole that would accommodate the α-amino group of N-termini of the peptide substrate. 
 
Design and synthesis of PfA-M1 selective inhibitors over mammalian counterpart 
as antimalarial agents and structural evaluation 
 
Library screening against PfA-M1 and PmAPN: 
Fresh stocks of all 40 compounds and control molecule actinonin were made in the 
dimethyl sulfoxide (DMSO) to a stock concentration of 10 mM. IC50 was determined 
against PfA-M1, PmAPN using seven different concentrations of inhibitor in the range 
between 0.016 µM and 100 µM at 200 µM of substrate (Leu-pNA) concentration. IC50 
data was determined using SigmaPlot 13. The Ki value for all compounds against PfA-
M1 was determined by the Dixon method using Leu-pNA as a substrate. The assay 
consists of reaction buffer, enzyme (0.1 µM) and Leu-pNA (30 µM, 80 µM, 200 µM, 
and 340 µM concentrations). At each substrate concentration, inhibitor concentration 
 Synopsis 
 
 xvii 
 
was varied in an appropriate range. Data were plotted as 1/rate vs. inhibitor 
concentration for each substrate concentration and a linear fit was calculated by non-
linear regression using SigmaPlot 13. All the experiments were carried out in triplicates 
and standard deviation (S.D) values were reported. All inhibitors tested were exhibited 
competitive inhibition. 
  
 Synopsis 
 
xviii 
 
Determination of inhibition constants (Ki) against PfA-M1: 
Compound 
Ki  against PfA-M1 
(µM±S.D) 
1 0.58±0.03 
2 0.42±0.02 
3 0.44±0.02 
4 0.35±0.01 
5 >500 
6 0.74±0.04 
7 0.87±0.04 
8 0.44±0.02 
9 0.14±0.01 
10 0.22±0.01 
11 0.24±0.03 
12 0.43±0.05 
13 0.26±0.01 
14 0.53±0.02 
15 0.09±0.008 
16 0.18±0.01 
17 0.24±0.01 
 
 
 
 
 
18 0.28±0.01 
19 0.09±0.006 
20 0.40±0.02 
21 0.16±0.02 
22 0.13±0.007 
23 0.19±0.01 
24 0.99±0.05 
25 1.06±0.05 
26 1.60±0.10 
27 2.61±0.13 
28 0.65±0.04 
29 0.76±0.04 
30 0.15±0.01 
31 0.84±0.05 
32 59.15±4.82 
33 113.04±11.86 
34 112.42±5.25 
35 209.66±12.91 
36 125.47±6.72 
37 75.11±4.98 
38 119.20±15.23 
39 0.05±0.005 
40 66.31±9.70 
Actinonin 9.49±0.69 
Bestatin 0.86±0.06 
 
Ki values were determined using Dixon plots of 1/rate versus inhibitor concentration for each 
substrate concentration. Substrate concentration was maintained lower than that of the Km of 
the enzyme. 
 


Understanding the Structural Differences Among M1-class Aminopeptidases and Development of Novel Inhibitors

V., Ponnilavan

Synthesis, structural insights and mechanical evaluation of selective rare-earth substitutions 
in zirconia toughened alumina system for hard tissue replacements 
 
The thesis work aimed to use rare earths as potential substitutions in ZTA system. Rare earth 
substitutions in ZTA system is attempted to impart dual features explicitly as a stabilizer and 
also to divulge additional features like fluorescence and MRI based imaging. Generally, 
imaging of prosthesis is done through the injection of a contrast agent to the patient in order 
to obtain better resolution image; however, side effects to the patient has been a major 
shortcoming that ranges from hypersentivity to mortality. Renal failure is the most common 
problem associated with the use of contrast agents. In this context, the inherent contrast 
features in ZTA facilitated by the inclusion of rare earths is expected to show a greater 
propensity for an easy monitoring of the implant performance through high resolution images 
and also avoid the ill side effects that are more palpable with the contrast agents. Thus, the 
outcome of thesis work is expected to provide a great impact in orthopedic surgeries as well 
as in imaging contrast tools. 


Synthesis, structural insights and mechanical evaluation of selective rare-earth substitutions in zirconia toughened alumina system for hard tissue replacements

Nanekar, Vikas

 
 
 
ABSTRACT 
 
Eulophia nuda Lindl [Synonym: E. spectabilis (Dennst.) Suresh] is a highly medicinal 
terrestrial orchid grows up to 75 cm with underground tubers and dark pinkish colour flowers 
(April-July), found in Southeast Asia. In India, this plant is found in tropical Himalayas 
(Uttarakhand, Assam, Arunachal Pradesh) and Western Ghat (Maharashtra, Karnataka, Kerala). 
Ethanobotanical studies revealed that its tubers are used against tumors, scrofulous glands of the 
neck, bronchitis, blood diseases, skin rash, rheumatoid arthritis, acidity, piles and stomach 
complaints, snake bite, tuberculosis, besides being used as a vermifuge, appetizer and an 
aphrodisiac drug. Further, pharmacological activities including anti-proliferative activities against 
cancerous cells, DNA damage protecting activities, anti-glycation, anti-inflammatory, 
antibacterial, antifungal and hepatoprotective activities have been reported from this plant. Though 
E. nuda is being used against many diseases by tribal communities and local healers, there are 
very few reports on scientific validation of its medicinal properties. Owing to its high therapeutic 
values, natural populations of E. nuda are under threat from over-exploitation and figured 
prominently in the Red Data book of IUCN and therefore need immediate steps for its 
conservation and large-scale propagation. 
 
Considering the importance of this plant and urgent need to conserve this plant, in-vitro 
tissue culture protocol was developed for E. nuda Lindl in which asymbiotic seed germination as 
well as direct and indirect organogenesis were successfully done. In-vitro asymbiotic seed 
germination is very crucial as orchids usually lack endosperm, and natural germination rate is very 
low and they often require fungal associations for their germination. In the present study, the seeds 
of different ages were germinated on half and full-strength MS (Murashige and Skoog), KC 
(Knudson) and BM1 terrestrial orchid (Van Waes and Debergh) media. Amongst various 
supplements, 15% coconut water (CW) and 500 mg l
-1
 casein hydrolysate proved beneficial for 
seed germination. BM1 fortified with CW showed the highest germination (80.5 ± 2.1%) after 60 
days of inoculation, which was further improved to 91.3 ± 1.9% upon incorporation of 1 mg l
-1
 
each of α-naphthaleneacetic acid (NAA) and 6-benzylaminopurine (BAP) and eventually more 
than 50% cultures developed into seedlings. BM1 containing CW nourished with 2.5 mg l
-1
 BAP 
and 1.5 mg l
-1
 kinetin (Kin) proved best for multiple shoot induction from seedlings. Shoot 
numbers increased further with successive transfers onto the same medium. Sixty shoots per shoot 
clump were achieved after four cycles of 30 days each. Microshoots were rooted on MS 
 
xii 
 
 
 
containing 2.0 mg l
-1
 indole-3 butyric acid (IBA) and 200 mg l
-1
 activated charcoal with 81.3 ± 
2.4% efficiency. Rooted plantlets were gradually acclimatized to greenhouse (70% survival) and 
they exhibited normal morphology and growth characteristics. Flow-cytometry based DNA 
content analysis revealed that the ploidy levels were maintained in in-vitro propagated plants. 
 
For direct and indirect organogenesis, various parameters including explant-type, medium 
compositions, use of phytohormones and additives (adenine sulfate, arginine, ascorbic acid and 
citric acid) were optimized for direct and indirect regeneration of E. nuda. Protocorms proved the 
best explants for shoot initiation, proliferation and callus induction. The MS medium containing 
2.5 mg l
-1
 6-benzylaminopurine (BAP), 1.0 mg l
-1
 Kin and additives (adenine sulfate, arginine, 
citric acid, 30 mg l
-1
 each and 50 mg l
-1
 ascorbic acid) was found optimal for shoot multiplication 
(12.1 shoots and 7.1 PLBs per explant with synchronized growth), besides producing basal-callus. 
Shoot number was further increased with three successive subcultures on the same media and ~40 
shoots per explant were achieved after 3 cycles of 30 days each. Additives (ascorbic acid, adenine 
sulfate and citric acid) and casein hydrolysate (CH) showed advantageous effects on indirect shoot 
regeneration via protocorm-derived callus. Optimum indirect regeneration was achieved on MS 
containing additives, 500 mg l
-1
 CH, 2.5 mg l
-1
 BAP and 1.0 mg l
-1
 Kin with 30 PLBs and 6 
shoots per callus mass (~5 mm size). The shoots were rooted (70% frequency) on ¼-strength MS 
medium containing 2.0 mg l
-1
 IBA, 200 mg l
-1
 activated charcoal and additives. The rooted 
plantlets were hardened and transferred to greenhouse with 63% survival rate. Flow-cytometry 
based DNA content analysis revealed that the ploidy levels were maintained in in vitro regenerated 
plants. 
 
In-vitro models confirmed strong dose-dependent antioxidant potentials of E. nuda tuber 
extracts. Petroleum ether (PEE), ethyl acetate (EAE), methanol (ME) and aqueous methanol 
(AqME) extracts (200-1000 µg ml
-1
 each) also showed significant free-radical scavenging 
potencies. Overall, the antioxidant efficacies were in the order EAE>ME>AqME>PEE. In-vitro 
cytotoxicity of two most-active extracts, EAE and ME were evaluated against human cancerous 
cells (MCF-7). EAE showed striking cytotoxicity, as only 0.86% cell survived at 1000 µg ml
-1
 
concentration, whereas 5.17% survival was recorded in presence of ME at same concentration. To 
identify and characterize phytochemical constituents, LC-ESI/MS profiling of most potent extract 
EAE was carried out, which revealed 37 identified compounds including catechin, 
 
 
 
xiii 
 
 
 
taxifolin, tocopherol, trigallic acid, pinoresinol and chlorogenic acid, all known for their strong 
antioxidant/anticancer properties. 
 
Phytochemical constituents and antioxidant efficacies of solvent-based extracts of E. nuda 
were investigated. Besides, the molecular mechanisms underlying strong antioxidant and 
antiproliferative activities, especially the via up-regulation of nuclear transcription factor-erythroid 
2 related factor (Nrf2) and hemeoxygenase-1 (HO-1) pathways was assessed, as Nrf2 is known as 
master regulator of antioxidant enzymes and HO-1 is its one of the target. Nrf2/HO-1 pathway has 
turn into a striking target for prevention and treatment of oxidative stress-associated maladies like 
cancer, neurodegenerative, cardiovascular, and inflammatory diseases. The expression levels of 
two key-factors in antioxidant systems- Nrf2 and HO-1 were therefore analyzed by qRT PCR in 
EAE-treated MCF-7 cells. Expression levels of both genes were upregulated beyond 50 µg ml
-1
 
extract concentration with > 2 - fold increase at 200 µg ml
-1
 EAE. Collectively, the data 
demonstrated that E. nuda extracts possess strong free radical scavenging and antioxidant 
efficacies and the mechanism of action be via inducing Nrf2 and HO-1. 
 
It was observed that phenolics were highly correlated with antioxidant activity and HR-
LC-MS proofing revealed presence of phenolic compounds including gallic acid, catechin, vanillin 
and quercetin etc and were mainly responsible for antioxidant activity. Hence the phenolics were 
elicited in in-vitro cultures using biotic and/or abiotic elicitors. Two endophytic fungi, fungal 
isolate III and fungal isolate IV identified as Fusarium proliferatum (Matsush.) and Talaromyces 
pinophilus (Hedgc.) on the basis of micromorphological and molecular characteristics (ITS4 and 
ITS5) with accession numbers MH636868 and MH685524, respectively. Water extracted mycelial 
polysaccharide from endophytic fungi isolated from rhizomes were used as biotic elicitors while 
methyl jasmonate (MJ) as signaling molecule, phenyl alanine (PA), sodium chloride (NaCl) and 
Calcium chloride (CaCl2) were used as abiotic elicitors. The biomass was harvested after two 
months. The growth was measured on the basis of fresh and dry weight of harvested biomass. The 
samples were dried in oven at 40ºC till they attained a constant weight. The dried samples were 
further employed for estimation of total polyphenols. Among the all biotic and abiotic elicitors; 
MJ and WEMP from F-IV (Talaromyces pinophilus) elicited the polyphenol in both callus as well 
as shoot culture when used singly. 
 
 
 
 
 
xiv 
 
 
 
Synergistic effects of biotic and abiotic elicitors were observed when cultures were treated 
with 100 mg l
-1
 WEMP F-IV (Talaromyces pinophilus) + 100µM MJ, as polyphenol production 
increased in shoot cultures. Estimation of individual phenolics including gallic acid, catechin, 
vanillin and quercetin showed their elicited production in shoot cultures with a clear indication of 
synergistic effect of WEMP and MJ, which was further confirmed by HPLC based estimation. 
Overall, 3.01-, 2.01-, 1.79-, 1.65-fold increase in gallic acid, catechin, vanillin and quercetin 
content, respectively, was recorded in in-vitro shoots over wild tubers (in vivo) , whereas 7.54-, 
3.13-, 2.03-, 1.73-fold increase, respectively, was evidenced in treated shoots apparently as a 
synergistic effect of biotic and abiotic elicitors [100 mg l
-1
 F-IV (Talaromyces pinophilus) + 
100µM MJ]. 
 
Asymbiotic seed germination, direct and indirect organogenesis of E. nuda, antioxidant 
and anti-proliferative potentials of solvent extracts of this orchid along with deciphering the 
molecular mechanisms underlying these strong activities via studying the Nrf2/HO-1 gene 
expression patterns in human cells treated with potent extract. The elicitation of important 
phenolics in in-vitro cultures of E. nuda using biotic and abiotic elicitors was also achieved 
successfully. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
xv 


IN-VITRO PROPAGATION, ANTIOXIDANT ACTIVITIES AND ELICITATION OF SECONDARY METABOLITES OF EULOPHIA NUDA LINDL

PAMARTHI, GANGADHAR

TOTAL SYNTHESIS OF BIOLOGICALLY ACTIVE POLYACETYLENES PETROSIOLS A AND E, STRONGYLODIOLS A, B, C, D, H AND I

MADHESHIYA, ABHISHEK

Preparation, Optical and Dielectric Properties of (PbxBi1-x)TiO3 (0.0 ≤ x ≤ 1.0) Borosilicate Glass and Glass Ceramics Doped with La2O3, CeO2 and Graphene Nanoplatlets

RANGARAJU, SUDHEERKUMAR

SYNERGISTIC GOLD AND COPPER DUAL CATALYSIS FOR INTER

AND INTRAMOLECULAR GLASER-HAY COUPLING: APPLICATION FOR TOTAL SYNTHESIS OF IVORENOLIDE B AND 1',8'- DIHYDROXY-3,4-DIHYDROVERNONIYNE

Undeela, Sridhar

Synopsis 
 
IV | P a g e  
 
The thesis entitled “Allenyl sulfones, sulfonamides and gold catalysts: A recipe for the 
rapid assembly of various nitrogen heterocycles” is divided into four chapters. 
 
CHAPTER- I: An introduction to homogeneous gold catalysis of organic reactions 
Homogeneous gold catalysis has provided remarkable contributions to organic 
transformations in past few years. Gold(I)complexes are effective catalysts for the 
electrophilic homogeneous activation of alkynes and for construction of carbon-carbon 
and carbon-heteroatom bond formation. Gold(I) complexes selectively activate π-bonds of 
alkynes in complex molecules. Gold-alkyne complexes readily undergo nucleophilic 
addition to form trans-alkene intermediate, which upon de-auration with proton or 
electrophile results trans-addition product (Figure 1). 
 
Figure 1: Gold catalyzed activation of alkynes and Markovnikov nucleophilic attack 
Gold complexes activates alkynes towards nucleophilic attack, inter- or intra-molecularly, 
due to relativistic effect, gold complexes possess high carbophilicity as compared to 
oxyphilicity. This ability of C-C multiple bond activation of gold allows for development 
of efficient catalytic methods for the formation of C-C, C-N, C-O and C-S bonds and often 
cyclization reactions. 
Transition metal catalyzed cycloisomerization of aza-enyne is a powerful method for 
construction of functionalized heterocycles. The significance of this process lies in the 
rapid increase of molecular complexity starting with relatively simple starting materials.  
Enyne cyclization pathways are highly influenced by substituents, the presence of 
electron-donating groups on alkyne favours 6-endo-dig cyclization pathway and electron-
withdrawing group on alkyne favours 5-exo-dig cyclization.  Enynes with terminal alkynes 
favours 5-exo-dig cyclization, internal alkynes favours 6-endo-dig cyclization (Figure 2). 
Synopsis 
 
V | P a g e  
 
 
Figure 2: Gold catalyzed enyne cycloisomerization 
CHAPTER-II: Base-mediated assembly of aza-enynes from allylbromo sulfones and 
their divergent gold-catalyzed cycloisomerization to pyrroles and dihydropyridines 
This chapter describes the base-mediated assembly of aza-enynes from bromoallyl 
sulfones and their divergent gold-catalyzed cycloisomerization to pyrroles and 
dihydropyridines. Divergent synthesis is strategy to synthesize a library of new chemical 
compounds from same building blocks with different reaction conditions. The work 
described in the chapter involves the divergent synthesis of pyrroles and dihydropyridines 
from the same set of reactants. A brief discussion on various divergent synthetic methods 
for heterocyclic construction, with an emphasis on aza-heterocycles, is presented in the 
beginning. The chemistry of allenyl sulfones remains less-explored due to the labile nature 
of this synthon and its anomalous behavior under various reaction conditions. A brief 
description of the chemistry of electrophilic allenes is presented in the introduction to put 
the results into perspective. 
The work described in this chapter involves various layers of new reaction discoveries. 
First a stable, synthetic surrogate for the labile allenyl sulfone was developed. The studies 
showed that the previously known allyl bromosulfone 1 can function as an equivalent of 
allenyl sulfone under basic conditions. They react with sulfonamides 2 under basic 
conditions to provide enamine-like products 3 that hold potential for further synthetic 
manipulations. Remarkably the reaction constitutes a formal, vinylic displacement of a 
bromide without using any transition metals (Scheme 1).  
Synopsis 
 
VI | P a g e  
 
25 °C
CH3CN
SO2Ph
(5:1 mixture)
PhO2S
•
72%
NH
SO2R
3
Cs2CO3
CH3CN
25 °C
N
SO2R
3
SO2R
4
R1 R
1
3, 55-94%
R2 R
2
SO2R
4
Br
SO2R
4
Br
1
2
 
Scheme 1: Base-mediated formal vinylic displacement reaction of 1 
The products 3 thus obtained were examined for their utility as building blocks for 
nitrogen heterocycles under gold catalysis. Details of the optimization study are presented 
in the Results and Discussion section. It was revealed that divergent cycloisomerisation 
pathways for formation of pyrroles or dihydropyridines can be mediated by different Au-
Ag catalyst combinations (Scheme 2).  
 
Scheme 2: Au-Ag catalyzed divergent cycloisomerisation of aza-enynes 3. 
Details of the scope, generality and further synthetic operations possible on the products 
are described in detail in this chapter (Scheme 3).  
Synopsis 
 
VII | P a g e  
 
NMe
SO2Ph
SO2Me
NBS
THF, 25 °C NMe
SO2Ph
SO2Me
Br
69%
N
Ts
SO2Me
H2, Pd/C
MeOH
25 °C
N
Ts
SO2Me
KOH
65 °C
12h
N
Ts
97%
98%
MeOH
 
Scheme 3: Synthetic modifications of pyrrole and dihydropyridine products 
A mechanistic postulate is also advanced wherein a propargyl-Claisen rearrangement is 
involved.  
 
CHAPTER-III: Cascade synthesis of substituted benzoisoquinoline derivatives via 
gold-catalyzed cascade cycloisomerization of enediynes  
This chapter describes the gold-catalyzed cascade cycloisomerization of ene-diynes 
synthesized using our formal vinylic displacement method. Cascade reactions, also known 
as a tandem or domino reactions, allows to carry out more than one transformation in an 
one-pot process without isolating any intermediate. The work described in this chapter 
involves the development of a god-catalyzed, cascade cycloisomerisation reaction of ene-
diynes 4. The latter compounds are synthesized in two steps as described in Scheme 4. 
Cs2CO3
25 °C, 2hCH3CN,
Br
SO2R
1
R1 = Ph, p-tolyl
NHMs
I I
N
Ms
SO2R
1
N
Ms
SO2R
1
R2
4
R2
PdCl2(PPh3)2, CuI
Et3N, THF, 25 °C, 2h
79% - 89%  
Scheme 4: Synthesis of ene-diynes 4 via formal vinylic displacement 
Explorations on the development of cascade cycloisomerisation reaction of these ene-
diynes are described in detail in this chapter. A facile reaction catalyzed by Au-Ag catalyst 
combination, that afforded 3,4-dihydrobenzo[f]isoquinolines 5 exclusively was discovered 
during these investigations (Scheme 5). 
 
Synopsis 
 
VIII | P a g e  
 
Au-Ag
Complete
regioselectivity
6-endo-dig
5
N
Ms
SO2R
1
R2
N
Ms
R2
b
[Au]
[Au]
SO2R
1
N
Ms
SO2R
1
[Au] R2
 
Scheme 5: Gold catalyzed cascade cycloisomerization of aza-ene-diyne. 
Substrates with heteroaromatic and aliphatic substituents on the alkyne end (R2) also 
produced good results, but in case of 2-ethynyl pyridine poor yield was observed. A 
mechanistic proposal and examples of further transformations of the product are also 
described in this chapter. 
 
CHAPTER-IV: Regioselective synthesis of 1-benzoazepine derivatives via gold-
catalyzed cycloisomerization of N-(o-alkynylaryl)-N-vinyl sulfonamides  
Benzo-fused, seven membered nitrogen heterocycles, commonly known as benzoazepines, 
are found in a variety of biologically active synthetic compounds. Benzoazepines are 
further classified based on the extent of unsaturation as well as the position of the nitrogen 
atom. Among them, the 1-benzoazepine moiety forms the core units of antagonists of N-
methyl-D-aspartate (NMDA), vasopressin V2 receptor, CC chemokine receptor-5 as well 
as anti-parasitic agents potentially useful for the treatment of leishmaniasis.  
The combination of vinylic displacement-gold-catalyzed cycloisomerisation was applied 
successfully for the synthesis of 1-benzoazepine derivatives too. The results are described 
in detail in this chapter. The precursors for cycloisomerisation were assembled using the 
formal vinylic displacement route. Subsequent gold-catalyzed cycloisomerisation 
proceeded with exclusive 7-endo regioselectivity to afford excellent yields of 
benzoazepine products 6 (Scheme 6).  
 
NHMs
SO2R
Ar
Br
I
Sonogashira
coupling
Formal vinylic
substitution
N
Ms
SO2R
Ar
2 steps
[Au]
N
Ms SO2R
Ar
78-92%
7-endo selective
Et3N
6
 
Scheme 6: Synthesis of N-(o-alkynylaryl)-N-vinyl sulfonamides and their gold catalyzed 
cycloisomerization. 
Synopsis 
 
IX | P a g e  
 
Analogous reactions on an aliphatic derivative 7 proceeded with a different 
regioselectivity to afford tetrahydropyrdine derivative 8 as the exclusive product (Scheme 
7). 
NHTs
Br
Ts
Cs2CO3
25 °C, 2h
CH3CN NTs
Ts CH2Cl2, 30 min.
2 mol% [Au]
[Au] = [JohnPhosAu(CH3CN)]SbF6
then Et3N
1 min, 25 °C
N
Ts
Ts
75%
7
8
 
Scheme 7: Gold-catalyzed cycloisomerization of aliphatic 3-aza-1,6-enyne 7 to afford a 4-
methylene tetrahydropyrdine derivative 8. 
Summary: A brief description of the newly discovered methodologies, importance of the 
products and potential future applications are described in this section.  
 


Allenyl sulfones, sulfonamides and gold catalysts: A recipe for the rapid assembly of various nitrogen heterocycles

GADDAM, JANARDHAN

Synopsis 
 
xi 
 
Ring-closing metathesis: Synthesis Relgro,10'-Oxorelgro, (3R,4S)-4-
Hydroxylasiodiplodin, (3R,4R)-4-Hydroxy-de-O-methyl-
lasiodiplodin, 8,9- Dihydrogreensporone D, Dechlorogreensporone F 
and Greensporone F. 
 
Chapter I: This chapter is further divided into two sections. 
Section A: Importance of natural product synthesis and a brief  
introduction to  Resorcylic acid lactones. 
Section B:Brief Introduction of Ring Closing Metathesis Reaction . 
 
Chapter II: Firsttotal syntheses of proposedstructures ofRelgro and    
10'-Oxorelgro  
 
Chapter-III: This chapter is further divided into two sections. 
Section A: Biological background of lasiodiplodins including its  
isolation and  previous  synthetic approaches. 
Section B: Stereo selective total Syntheses of (3R,4S)-4-hydroxylasio 
diplodin and (3R,4R)-4-hydroxy-de-O-methyllasiodiplodin. 
 
Chapter-IV: FirstStereoselective total Syntheses of 8,9- Dihydrogreen 
sporone D, Dechlorogreensporone F and Greensporone F. 
 
 
 
 
Synopsis 
 
xii 
 
CHAPTER I: 
Statement of problem: Importance of natural product synthesis and a brief 
introduction to Resorcylic acid lactones. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
CHAPTER II 
Introduction: 
 A 10-membered β-resocylic macrolide, relgro was isolated along with other 
metabolites by panichlert et al., from the seagrass-derived fungus Fusarium 
sp. PSU -ES73. The fungus obtained from the leaves of T.hemprichiiseagrass 
found in Trang Province, Thailand. P.Saetang and co-workers established 
absolute configuration of relgro and 10'-Oxorelgro in 2016.  
 Structurally, relgro has two stereogeniccenters at C-6' and C-10' whereas 10'-
Oxorelgro has only one stereogeniccenters at C-6' and carbonyl functionality 
at C-10'. The absolute configuration at C-6' was assigned by comparing the 
Cotton effect at 266 nm in CD spectrum with that of 3R, 5S-Sonnerlactone 
and the absolute configuration of the secondary alcohol at C-10 was 
determined on the basis of Mosher ester analysis. 
O
O
OH
OH
OH
OH
H3CO O
Paecilomycin A
O
OOH
H3CO
O
HO OH
OH
Paecilomycin B Paecilomycin F : R1=H. R2 =OH
Paecilomycin E : R1=OH. R2 =H
O
O
OH
R2
OH
OH
H3CO R1
O
O
N
H
O
OH
O
OH
Apicularen A
O
Apicularen B
CH2OHHO
AcHN
H
OH
O
O
O
N
H
O
OH
O
O
OH
HO
O
O
O
OH
HO
O
O
O
OH
HO
O
O
OH OH
Xestodecalactone A Xestodecalactone B Xestodecalactone C
O
HO
O
O
OH
(3S, 6R)-6- hydroxy-
lasiodiplodin
OH
HO
O
O
O
trans-resorcylide
Synopsis 
 
xiii 
 
Statement of problem: First total syntheses of Relgro, 10'-Oxorelgro and its 
structural elucidation. 
Retrosynthetic analysis of Relgro and 10'-Oxorelgro 
O
O
HO
OH
OH
OH
O
BnO
OH
+
OH
OH
O
HO
OH
O
1. R1 = H, R2 = OH
2. R1 = R2 = O 4
5 67
R2R1
O
O
BnO
OH
8
OTBS
OTBS
 
Results anddiscussion:  
 
The total synthesis of Relgro and 10'-Oxorelgro commenced with commercially 
available 2,4,6-trihydroxybenzoic acid 7.This synthesis has been achieved using 
following key reactions: Stille coupling to obtain aromatic acid 5 andchiral epoxide 
8, Jocobsen kinetic resolution  to yield alcohol 6, the coupling reaction of fragments 
by utilisingEDC promoted coupling and RCM reaction. 
Scheme 1.Synthesis of  fragment5 
 
 
 
Synopsis 
 
xiv 
 
Scheme 2.Synthesis of Fragment 6 
 
 
Scheme 3.Coupling of the fragments 5 and 6: 
 
 
Scheme 4.Total Synthesis of the 10'-Oxorelgro (2): 
CH2Cl2, rt
2 h, 82%
O
O
OH
HO
OH
1
O
O
O
HO
OH
10'-oxorelgro (2)
PCC
 
 
 
Synopsis 
 
xv 
 
Conclusion: 
In summary, we have successfully accomplished the first total synthesis of proposed 
relgro (1) and 10′-oxorelgro (2) with good overall yield. Our synthetic investigations 
revealed that the reported structure of relgro (1) and 10′-oxorelgro (2) needs revision. 
We hereby suggesting the structure of relgro might be with 6′S, 10′S configuration. 
The real structure of 10′-oxorelgro (2) might be with 6′S configuration. The synthetic 
strategy delineated here includes Stille coupling, EDCI promoted coupling reaction, 
Jacobsen hydrolytic kinetic resolution and ring-closing metathesis. The synthetic 
strategy explored here may also be useful to synthesize a number of related RALs. 
Further, synthetic efforts towards structural verification of relgro and 10′-oxorelgro 
under investigation in our laboratory. 
 
CHAPTER III: 
Statement of problem:Stereoselective total Syntheses of (3R,4S)-4-
hydroxylasiodiplodin,  (3R,4R)-4-hydroxy-de-O-methyl-lasiodiplodin. 
 
Scheme 1.Retrosynthetic Analysis of (3R,4S)-4-hydroxylasiodiplodin  (1) 
 
 
 
Synopsis 
 
xvi 
 
Results and discussion: 
Scheme 2.Synthesis of epoxide fragment 4 
 
OH
OOH
OHHO
OH
O
BnO
OH
6
4
5 steps
 
 
 
Scheme 3. Synthesis fragment 6 
 
 
 
 
Synopsis 
 
xvii 
 
Scheme 4. Total Synthesis (3R,4S)-4-hydroxylasiodiplodin  (1) 
 
 
Retrosynthesis of (3R,4R)-4-hydroxy-de-O-methyl-lasiodiplodin (2) 
 
O
OOH
HO
OH
OH
OOH
BnO
HO
OPMB
+
OH
OOH
OHHO
HO
OH O
OPMB
OTBS
2
5 207
21
9
O
OOH
BnO
OPMB
O
OOH
BnO
OPMB
18 19
 
 
 
Synopsis 
 
xviii 
 
Scheme 3. Synthesis fragment 20  
 
Scheme 3.Total synthesis of (3R,4R)-4-hydroxy-de-O-methyl-lasiodiplodin (2) 
Conclusion: 
We have demonstrated an efficient, highly stereoselective approach to accomplish 
the first total synthesis of (3R,4R)-4-hydroxy-de-O-methyl-lasiodiplodin from 
commercially available 1,6-hexanediol. The total synthesis of (3R,4S)-4-
hydoxylasiodiplodin has been accomplished by employing palladium catalyzed Stille 
coupling, EDC promoted coupling and ring-closing metathesis as the key steps. This 
method can be conveniently utilized for the synthesis of different other resorcylic 
macrolides towards the development of such class of compounds. 
CHAPTER IV 
Introduction: 
In 2014 Nicholas H. oberlier reported the isolation of 14 new 14-membered 
resorcyclicacid  lactones from fresh water aquatic fungus Halenospora sp. collected  
in North Carolina. All these structures were elucidated through spectrometric and 
Synopsis 
 
xix 
 
spectroscopic techniques.   Except 8 and 12, all isolated compounds were tested 
against 2 cancer cell lines that are HT- 9(Colon) and MDA-MB-435(Melanoma). 
Statement of problem: First Stereoselective total Syntheses of 8,9- 
dihydrogreensporone D, Dechlorogreensporone F and Greensporone F. 
Scheme 1.Retrosynthetic analysis 
 
 
 
Synopsis 
 
xx 
 
Results anddiscussion:  
Scheme 2.Synthesis of aldehyde fragment 7 
 
 
Scheme 3.Synthesis of sulphone fragment 8 
 
 
 
Scheme 4. Coupling of fragments 7 and 8 
Synopsis 
 
xxi 
 
 
Scheme 5.Total synthesis 8,9- dihydrogreensporone D (1) and Greensporone F 
(2). 
 
 
 
Scheme 6. Total synthesis of Dechlorogreensporone F (3) 
Synopsis 
 
xxii 
 
 
Conclusion: 
The First total syntheses of 8,9-Dihydrogreensporone D (1), Greensporone F (2)and 
Dechlorogreensporone F (3) have been achieved in a concise manner following  
Danishefsky reaction, Mitsunobu reaction,Stille cross coupling, acid catalyzed 
transannularoxa-Michael cyclization, ring-closing metathesis (RCM) reaction, and 
De Brabander’s esterification  as key reactions. The strategy delineated here can be 
useful for the synthesis of other related RALs. 
 
 


Ring Closing Metathesis: Synthesis of Relgro, 10'-Oxorelgro, (3R, 4S)-4-Hydroxylasiodiplodin, (3R, 4R)-4-Hydroxy-de-O-methyllasiodiplodin, 8,9-Dihydro greensporone D, Dechloro greensporone F and Greensporone F

KANIKARAPU, SURESH

  
                                                                                                                                                                            Synopsis 
I 
 
SYNOPSIS 
The thesis entitled “Studies Towards Synthesis of the Bioactive Natural Products: 
4,8-Dihydroxy-3,4-dihydrovernoniyne, Brevipolide H and (+)-Ambruticin F” has been 
divided into three chapters. 
CHAPTER I             : This chapter is further subdivided into two sections. 
Section A          : This section deals with the brief discussion of acetylenic compounds:   
Isolation, biological activity, synthesis of di, tri, tetra and poly acetylene 
compounds. 
Section B : This section describes the total Synthesis and Stereochemical Revision of 
4,8-Dihydroxy-3,4-dihydrovernoniyne. 
CHAPTER II  : This chapter is further subdivided into two sections. 
Section A : This section deals with the brief introduction of cyclopropane 
containing molecules including their isolation, biological activity and 
previous synthetic approaches of brevipolide H.  
Section B  : This section describes toward the synthesis of brevipolide H. 
Section C                    : This section describes Convergent formal Synthesis towards Brevipolide 
H. 
CHAPTER III : This chapter is further subdivided into two sections. 
Section A                    : This section deals with the brief introduction and previous approaches 
for  (+)- Ambruticin S. 
Section B : This section describes Synthesis of the C1–C8 Fragment and C17–C24 
Fragment of (+)-Ambruticin F by Following Tandem Isomerization 
Followed by C-O/C-C Bond Formation Reaction. 
 


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