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1.
Viruses ; 15(9)2023 08 28.
Article in English | MEDLINE | ID: mdl-37766233

ABSTRACT

Antiviral properties of different oxa- and aza-heterocycles are identified and properly correlated with their structural features and discussed in this review article. The primary objective is to explore the activity of such ring systems as antiviral agents, as well as their synthetic routes and biological significance. Eventually, the structure-activity relationship (SAR) of the heterocyclic compounds, along with their salient characteristics are exhibited to build a suitable platform for medicinal chemists and biotechnologists. The synergistic conclusions are extremely important for the introduction of a newer tool for the future drug discovery program.


Subject(s)
Antiviral Agents , Drug Discovery , Antiviral Agents/pharmacology , Structure-Activity Relationship
2.
J Org Chem ; 88(18): 12872-12883, 2023 Sep 15.
Article in English | MEDLINE | ID: mdl-36007267

ABSTRACT

The synthesis of highly functionalized five-membered oxa- and aza-heterocycles has been reported utilizing hydrogen-bond donor (HBD) catalysis. In this method, an epoxide was taken as a substrate and reacted with functionalized arylidene/alkylidene malononitrile derivatives in the presence of a newly designed HBD catalyst. In all the cases, the products 2,5-disubstituted tetrahydrofurans (2,5-THFs) were obtained in good to excellent yields (up to 86%) with high diastereoselectivity (dr up to 99:1) as a single regioisomer. The stereochemistry at the 2- and 5-positions of the five-membered ring has been confirmed by single-crystal X-ray analysis, and cis is found to be the major product. The same strategy has been further utilized to obtain substituted oxazolidines whenever the epoxide has been reacted with isocyanate as an electrophile. In order to induce enantioselectivity, a chiral epoxide has been reacted with both the electrophiles in the presence of the same catalyst system to afford the single stereoisomer of the final products. This synthetic methodology involves a low catalyst loading and ambient reaction condition and has been generalized with various substituents present in the starting electrophiles to produce the resultant products in acceptable yields and stereoselectivity.

3.
J Org Chem ; 80(19): 9700-12, 2015 Oct 02.
Article in English | MEDLINE | ID: mdl-26334184

ABSTRACT

A simple strategy for the synthesis of highly functionalized cyclohexanone derivatives containing an all-carbon quaternary center from α-(aryl/alkyl)methylidene-ß-keto esters or ß-diketones via a K-enolate mediated domino Michael-Michael reaction sequence with moderate to good yield and excellent diastereoselectivity (de > 99%) is described. Interestingly, Li-base mediated reaction of α-arylmethylidene-ß-diketones affords functionalized 3,5-dihydroxy cyclohexane derivatives as the kinetically controlled products via a domino aldol-aldol reaction sequence with excellent diastereoselectivity. Li-enolates of the ß-keto esters or ß-diketones undergo facile domino Michael-Michael reaction with nitro-olefins to afford the corresponding nitrocyclohexane derivatives in good yields and excellent diastereoselectivity (de > 99%). The formation of the products and the observed stereoselectivity were explained by plausible mechanisms and supported by extensive computational study. An asymmetric version of the protocol was explored with (L)-menthol derived nonracemic substrates, and the corresponding nonracemic cyclohexanone derivatives containing an all-carbon quaternary center were obtained with excellent stereoselectivity (de, ee > 99%).

4.
Org Biomol Chem ; 12(19): 3037-44, 2014 May 21.
Article in English | MEDLINE | ID: mdl-24671378

ABSTRACT

A new pyrene based fluorescence probe has been synthesized for fluorogenic detection of Cu(2+) in acetonitrile-aqueous media (7 : 3 CH3CN-HEPES buffer, v/v, at pH 7.5) with bioimaging in both prokaryotic (Candida albicans cells) and eukaryotic (Tecoma stans pollen cells) living cells. The anion recognition properties of the sensor have also been studied in acetonitrile by fluorescence methods which show remarkable sensitivity toward fluoride over other anions examined.


Subject(s)
Bignoniaceae/cytology , Candida/cytology , Copper/analysis , Fluorescent Dyes/chemistry , Fluorides/analysis , Pyrenes/chemistry , Anions , Cell Survival , Fluorescent Dyes/chemical synthesis , Proton Magnetic Resonance Spectroscopy , Spectrometry, Fluorescence , Spectrophotometry, Ultraviolet
5.
J Org Chem ; 79(6): 2682-7, 2014 Mar 21.
Article in English | MEDLINE | ID: mdl-24559471

ABSTRACT

HMPA is known to increase the reduction potential of SmI2. However, in many cases, the transferred electron returns from the radical anion of the substrate back to the Sm(3+). This could be avoided by an efficient trapping of the radical anion: e.g., by protonation. However, bimolecular protonation by a proton donor from the bulk may be too slow to compete with the back electron transfer process. An efficient unimolecular protonation could be achieved by using a proton donor which complexes to SmI2, in which case the proton is unimolecularly transferred within the ion pair. A derivative of HMPA in which one of the methyl groups was substituted by a CH2CH2OH unit was synthesized. Cyclic voltammetry studies have shown that it resembles HMPA in its ability to enhance the reduction potential of SmI2, and reactivity studies show that it has also efficient proton shift capabilities. The various aspects of this additive were examined in the reactions of SmI2 with three substrates: benzyl chloride, methyl cinnamate, and anthracene.

6.
Analyst ; 138(6): 1903-7, 2013 Mar 21.
Article in English | MEDLINE | ID: mdl-23392200

ABSTRACT

A new rhodamine-quinoline based dyad has been synthesized. It shows a highly selective response to Cd(2+) in the presence of other competing metal ions in aqueous media (pH = 7.1). The detection limit of the sensor is in the 10(-7) M level.


Subject(s)
Cadmium/analysis , Fluorescent Dyes/chemistry , Quinolines/chemistry , Rhodamines/chemistry , Spectrometry, Fluorescence/methods , Water Pollutants, Chemical/analysis , Cations, Divalent/analysis , Colorimetry , Limit of Detection , Water/analysis
7.
J Org Chem ; 78(6): 2311-26, 2013 Mar 15.
Article in English | MEDLINE | ID: mdl-23320819

ABSTRACT

A simple strategy for the synthesis of chiral α,ß-diamino- and α-amino,ß-hydroxy ester derivatives in high yields with moderate to high ee has been developed via asymmetric imino-aldol and aldol reactions, respectively, starting from protected aminoesters employing memory of chirality concept for chiral induction. This strategy has been extended for the enantioselective synthesis of aziridines (ee up to 92%). The absolute configuration of the imino-aldol adducts has been determined. The stereochemical outcome of the products has been explained by a suitable mechanism and supported by computational studies.


Subject(s)
Amino Acids, Diamino/chemistry , Aziridines/chemistry , Aziridines/chemical synthesis , Imines/chemistry , Amino Acids, Diamino/chemical synthesis , Catalysis , Computer Simulation , Esters , Molecular Structure , Stereoisomerism
8.
J Org Chem ; 75(21): 7061-72, 2010 Nov 05.
Article in English | MEDLINE | ID: mdl-20932043

ABSTRACT

Addition of α-arylmethylidene- or α-alkylidene-ß-keto ester enolate to N-activated aldimines via the imino aldol pathway followed by intramolecular aza-Michael reaction in a domino fashion has been developed, and a highly diastereoselective route to substituted piperidines is reported. Enantiopure piperidines are synthesized from chiral sulfinyl imines. Formation and the observed stereoselectivity of the products have been rationalized by mechanistic and computational studies.


Subject(s)
Imines/chemistry , Piperidines/chemistry , Piperidines/chemical synthesis , Stereoisomerism , Substrate Specificity
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