1,720,980 research outputs found
Structural insights into methyl- or methoxy-substituted 1-(α-aminobenzyl)-2-naphthol structures: the role of C—H...π interactions
No full textAminobenzylnaphthols are a class of compounds containing a large aromatic molecular surface which makes them suitable candidates to study the role of C-H...π interactions. We have investigated the effect of methyl or methoxy substituents on the assembling of aromatic units by preparing and determining the crystal structures of (S,S)-1-{(4-methylphenyl)[(1-phenylethyl)amino]methyl}naphthalen-2-ol, C26H25NO, and (S,S)-1-{(4-methoxyphenyl)[(1-phenylethyl)amino]methyl}naphthalen-2-ol, C26H25NO2. The methyl group influenced the overall crystal packing even if the H atoms of the methyl group did not participate directly either in hydrogen bonding or C-H...π interactions. The introduction of the methoxy moiety caused the formation of new hydrogen bonds, in which the O atom of the methoxy group was directly involved. Moreover, the methoxy group promoted the formation of an interesting C-H...π interaction which altered the orientation of an aromatic unit
Stereoselection in the Betti reaction of valine methyl esters
No full textThe multi-component Betti reaction of 2-naphthol, benzaldehyde and (S)-amines, that usually provides highly valuable aminobenzylnaphthol bearing two stereogenic centers, yielded a completely racemic product, when (S)-valine methyl ester was employed as the amine in the usual reaction protocol. The cause of this drawback, that appears to be overlooked in the literature, was investigated. As a result, new reaction conditions were set up, that were able to yield the expected useful product, having two fully resolved stereogenic centers. Furthermore, when the effect of substituents on the phenyl ring was preliminarily studied, we found that 4-fluoro- and 4-chlorobenzaldeyde gave stereoisomerically pure compounds also in the original reaction protocol
Antiproliferative Activity of Aminobenzylnaphthols Deriving from the Betti Reaction
Full text linkTwo aminobenzylnaphthols, which are representative items of the family of compounds synthesized with the Betti reaction, were investigated as antiproliferative agents against adenocarcinoma human colorectal (Caco-2) and human neuroblastoma (SH-SY5Y) cell lines, using cisplatin as a positive control. A better antiproliferative activity was recorded after 24 h of incubation for the first tested molecule, whereas the other one was more effective after 72 h of incubation. These results support the hypothesis that both of the tested aminobenzylnaphthols could potentially be endowed with a biological activity
L’attualità delle ricerche di Mario Betti (1875-1942)
No full textMario Betti was a distinguished Italian chemist of the early 20th century. He investigated many research fields, but he is particularly known for innovative syn- thetic reactions and for his research in asymmetric synthesis. However, his work was al- most forgotten until the end of the 20th century, when the group of Naso and Cardellic- chio in Bari brought to the attention of the organic chemistry community a new re- search, inspired from the work of Betti. Since then, many research groups around the world have applied this old chemistry, that is still interesting and abreast of contempo- rary synthetic problems
A dichotomy in the enantioselective oxidation of aryl benzyl sulfides: A combined experimental and computational work
No full textPentafluorobenzyl pentafluorophenyl sulfide is oxidised with moderate e.e. value and a low yield by the usually highly successful oxidation protocol based upon tert-butyl hydroperoxide (TBHP) in the presence of a titanium/hydrobenzoin complex. This disappointing result resisted until the present work, in which the switch of the oxidation agent (from TBHP to cumene hydroperoxide), suggested by our previous computations, yielded the enantiopure sulfoxide. This valuable chiral compound was obtained in good yields (76%) without resorting to a chromatographic separation. DFT computations uncovered that this favourable reactivity was originated by a stabilizing π−π−stacking between the phenyl group of the oxidant and the pentafluorophenyl moiety of the substrate
Investigation on the Crystal Structures of Molecules Related to 2‐(Benzylsulfinyl)Benzoic Acid, As a Support to the Studies on the Inhibition of Human Carbonic Anhydrases
No full textA recent interest attaches to the derivatives of the (2-benzylsulfinyl)benzoic acid as inhibitors of human carbonic anhydrases (hCAs), an action that can be applied in innovative therapies. A set of crystal structures of six sulfides and six enantiopure sulfoxides related to this scaffold, taken from the literature, or derived from the work on the asymmetric synthesis of sulfinyl compounds, is investigated. The lattice energies of these structures are estimated by means of the Crystal Explorer 21 program. The weak interactions building up the crystal structures are identified, and their contributions are analyzed in comparison with the calculated lattice energies. The most stable conformations in the solid phase are identified. It is worth observing that the sulfides of the scaffold under investigation behave almost in the same manner; on the other hand, the presence of the sulfinyl group of the sulfoxides adds complexity, that shall be taken into account in future docking calculations of these molecules with the hCAs enzymes
Investigation of the titanium-mediated catalytic enantioselective oxidation of aryl benzyl sulfides containing heterocyclic groups
No full textOur enantioselective oxidation protocol, based upon hydroperoxides in the presence of a titanium/(S,S)-hydrobenzoin catalyst, was tested for the first time with aryl benzyl sulfides containing heterocyclic moieties (2-thienyl, 2-pyridyl and benzimidazolyl), two of them being connected with the blockbuster omeprazole drug. Good yields of enantiopure sulfoxides were obtained in most cases. Two exceptions of unsatisfactory enantioselectivity in the oxidation of benzimidazolyl sulfides are reported. However, one of them was solved by crystallization of an enantio-enriched mixture. The present work was supported also by X-ray diffraction analysis of some synthesized sulfoxides and by energetic calculation of the crystal structures. The unexpected result is that the crystal structures of the racemic mixture of the two problematic benzimidazolyl sulfoxides are composed of separate enantiomers (a conglomerate), an interesting result that could be exploited in the future for the separation of the enantiomers of these sulfoxides
Circular Dichroism and TDDFT Investigation of Chiral Fluorinated Aryl Benzyl Sulfoxides
No full textA series of ten chiral aryl benzyl sulfoxides with perfluorinated aryl or benzyl rings, obtained by enantioselective oxidation of sulfides, has been investigated by means of electronic circular dichroism (ECD) spectroscopy and time-dependent DFT (TDDFT) calculations. The (per)fluorination of the aromatic rings has a large impact on the conformer population, the molecular orbitals shape, and the character of electronic transitions. In this series, the transition responsible for the “sulfoxide primary” CD band has a large charge transfer (CT) character, as demonstrated by the CT metric index ΓNTO. As a consequence, global DFT hybrids such as B3LYP are largely inaccurate in the prediction of excited states; nevertheless, a correct simulation of CD spectra may be achieved by using range-separated functionals such as CAM-B3LYP. The use of the empirical Mislow's rule for assigning the absolute configuration is strongly discouraged for this class of compounds
Asymmetric Chemoenzymatic Synthesis of 1,3-Diols and 2,4-Disubstituted Aryloxetanes by Using Whole Cell Biocatalysts
Full text linkRegio- and stereoselective reduction of substituted 1,3-aryldiketones, investigated in the presence of different whole cell microorganisms, was found to afford β-hydroxyketones or 1,3-diols in very good yields (up to 95%) and enantiomeric excesses (up to 96%). The enantiomerically enriched aldols, obtained with opposite stereo-preference by baker’s yeast and Lactobacillus reuteri DSM 20016 bioreduction, could then be diastereoselectively transformed into optically active syn- or anti-1,3-diols by a careful choice of the chemical reducing agent (diastereomeric ratio up to 98:2). The latter, in turn, were stereospecifically cyclized into the corresponding oxetanes in 43–98% yields and in up to 94% ee, thereby giving a diverse selection of stereodefined 2,4-disubstituted aryloxetanes
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