37 research outputs found
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Part I: Total synthesis of marine macrolide amphidinolide F and synthetic studies toward amphidinolide C; Part II: Computational study on proline sulfonamide-catalyzed aldol reaction
No full textMore than 30 members of the diverse amphidinolide family of biologically active macrolides have been isolated over last three decades. From this family, amphidinolides C and F stand among the most complex and densely functionalized affiliates. Recently, we have accomplished the first total synthesis of amphidinolide F. The all-carbon framework of amphidinolide C has been synthesized.
During endeavor toward the total syntheses of amphidinolides F / C, we have uncovered a "hidden symmetry element" present in the northern and southern domains of amphidinolides F / C. The southern C₁-C₈ and northern C₁₈-C₂₅ tetrahydrofuran segments were derived from a common intermediate. A scalable silver-catalyzed isomerization / cyclization on propargyl-benzoate / diol furnished the common intermediate in multigram quantity. The common intermediate provided access to over half of carbon backbone of the macrocycle as well as majority of stereochemistry present in amphidinolides F / C.
Two strategically different techniques have been developed for the C₉-C₁₁ diene preparation. A metal-catalyst free Weinreb amide-vinyl lithium coupling / methylenation sequence furnished the diene motif. Alternately, diastereoselective addition of a dienyl iodide derived 2-lithio-1,3-diene species to an α-oxy aldehyde installed the C₉-C₁₁ diene and secured the C₈ stereochemistry in single operation. The dienyl iodide was prepared via a regioselective hydrostannylation on an enyne.
A challenging alkylation between an α-branched sulfone and an α-silyloxy iodide generated the all-carbon frameworks of amphidinolides F / C. An efficient oxidative desulfurization incorporated the carbonyl moiety at C₁₅. The protecting group on C₁₈ alcohol was found to have significant effect on the sulfone-iodide alkylation / oxidative desulfurization sequence. Installation of chelating ethoxyethyl ether on C₁₈ alcohol helped the successful incorporation of C₁₅ ketone and solved the deprotection problem in advanced stage of synthesis.
A detailed analytical and computational study on proline sulfonamide-catalyzed aldol reactions has been performed. The pKa value of a proline sulfonamide catalyst was determined experimentally via NMR titration technique. Computational study revealed the origin of enhanced stereoselectivity by proline sulfonamide catalysts over parent proline. The non-classical hydrogen bonding interactions were found to be responsible for improved diastereoselectivity
Cover Picture: Enantioselective Total Synthesis of Amphidinolide F (Angew. Chem. Int. Ed. 32/2012)
No full text
Economic Benefits of NPK and Organic Amendments on Green Gram Yield
No full textThe research study titled Economic benefits of application of NPK, fermented organic manures and mycorrhiza on yield and production of green gram (Vigna radiata L.) Var. PDM-139." was conducted during the Zaid season of 2023 at the Central Research Farm, Department of Soil Science and Agricultural Chemistry, Naini Agricultural Institute, Sam Higginbottom University of Agriculture, Technology, and Sciences, Prayagraj, Uttar Pradesh, India. The experimental layout followed a 3x3 Randomized Block Design (RBD), incorporating three levels of fermented organic manure (0%, 50%, and 100%), Mycorrhiza (0%, 50%, and 100%), and N, P, K at the Recommended Dose of Fertilizers (RDF). The variety chosen was PDM-139, which was released by the State Variety Release Committee (SVRC) of Uttar Pradesh in 1974. The recorded average yield ranged from 6 to 9 quintals per hectare. The response of total seed yield of green gram recorded as influenced by different levels NPK, fermented organic manure and mycorrhizal inoculation. The seed yield of green gram was found to be increased significantly with the increase in levels of NPK, fermented organic manure and mycorrhizal inoculation. The maximum seed yield was recorded as 16.42 (q ha-1) T9 (NPK@RDF + M2@ 10Kg ha-1 50% + F2@ 50 l ha-1 50%) which was higher than any other treatment combination and the minimum seed yield was recorded as 8.76 (q ha-1) in T1 (control). However, as for the economy of different treatments is concerned, the treatment T9 (NPK@RDF + M2@ 10Kg ha-1 50% + F2@ 50 l ha-1 100%) provide highest net profit of ₹ 68139.13 ha-1 with highest cost benefit ratio is 1:1.605
Palladium‐Catalyzed CH Activation of N‐Allyl Imines: Regioselective Allylic Alkylations to Deliver Substituted Aza‐1,3‐Dienes
No full textChemInform Abstract: Palladium‐Catalyzed C—H Activation of N‐Allyl Imines: Regioselective Allylic Alkylations to Deliver Substituted Aza‐1,3‐Dienes.
No full textExploiting Hidden Symmetry in Natural Products: Total Syntheses of Amphidinolides C and F
No full textThe total synthesis of amphidinolide
C and a second-generation
synthesis of amphidinolide F have been accomplished through the use
of a common intermediate to access both the C1–C8 and the C18–C25 sections. The
development of a Ag-catalyzed cyclization of a propargyl benzoate
diol is described to access both trans-tetrahydrofuran
rings. The evolution of a Felkin-controlled, 2-lithio-1,3-dienyl addition
strategy to incorporate C9–C11 diene
as well as C8 stereocenter is detailed. Key controlling
aspects in the sulfone alkylation/oxidative desulfurization to join
the major subunits, including the exploration of the optimum masking
group for the C18 carbonyl motif, are discussed. A Trost
asymmetric alkynylation and a stereoselective cuprate addition to
an alkynoate have been developed for the rapid construction of the
C26–C34 subunit. A Tamura/Vedejs olefination
to introduce the C26 side arm of amphidnolides C and F
is employed. The late-stage incorporation of the C15, C18 diketone motif proved critical to the successful competition
of the total syntheses
Exploiting Hidden Symmetry in Natural Products: Total Syntheses of Amphidinolides C and F
No full textThe total synthesis of amphidinolide
C and a second-generation
synthesis of amphidinolide F have been accomplished through the use
of a common intermediate to access both the C1–C8 and the C18–C25 sections. The
development of a Ag-catalyzed cyclization of a propargyl benzoate
diol is described to access both trans-tetrahydrofuran
rings. The evolution of a Felkin-controlled, 2-lithio-1,3-dienyl addition
strategy to incorporate C9–C11 diene
as well as C8 stereocenter is detailed. Key controlling
aspects in the sulfone alkylation/oxidative desulfurization to join
the major subunits, including the exploration of the optimum masking
group for the C18 carbonyl motif, are discussed. A Trost
asymmetric alkynylation and a stereoselective cuprate addition to
an alkynoate have been developed for the rapid construction of the
C26–C34 subunit. A Tamura/Vedejs olefination
to introduce the C26 side arm of amphidnolides C and F
is employed. The late-stage incorporation of the C15, C18 diketone motif proved critical to the successful competition
of the total syntheses
