Surendra Singh Bisht

Application of Huisgen (3 + 2) cycloaddition reaction: Synthesis of 1-(2,3-dihydrobenzofuran-2-yl-methyl [1,2,3]-triazoles and their antitubercular evaluations

1,4-Disubstituted-1,2,3-triazoles (3-27) have been synthesized by [3+2] cycloaddition of different 2-(azidomethyl)-dihydronaptho(benzo)furans (2a, 2b, 2c and 2d) with different alkynes. All the compounds were screened for antitubercular activity against Mycobacterium tuberculosis H37Rv. Compounds 2a, 7, 9, 12 and 14 exhibited antitubercular activities with MIC ranging from 12.5 to 3.12 microg/ml.

Synthesis and molecular docking studies of 1-phenyl-4-glycosyl-dihydropyridines as potent antileishmanial agents

A series of 1-phenyl-4-glycosyl-dihydropyridines (4-17 and 19-21) were prepared by the one pot multicomponent reaction of glcosyl aldehyde, beta-keto compounds and aniline or substituted aniline in the presence of TBAHS as catalyst. The compounds were screened in vitro and in vivo for their antileishmanial activities. Most of the compounds exhibited moderate to good activity against amastigotes and promastigotes of Leishmania donovani. The compounds 4, 11, 12, 13, and 17 exhibited potent in vivo activity with selectivity index (SI) values 7.43-18.93. Molecular docking studies with these compounds revealed L. donovani PTR1 as the possible target to show antileishmanial activities.

L-Ascorbic acid in Organic Synthesis: An Overview

L-Ascorbic acid, commonly known as vitamin C is well-known in chemistry since long back. It has tremendous medical applications in several diseases. However, application of this chiral molecule in organic synthesis has been neglected earlier. In the later part of twentieth century application of ascorbic acid has gained momentum in organic synthesis of different molecules of biological importance and of chemotherapeutic significance. We have given an account of the history, chemistry, biochemistry and biosynthesis of ascorbic acid and application of this small molecule in organic synthesis. The application of ascorbic acid in accessing chiral synthons has also been described.

Aldol reaction of β-C-glycosylic ketones: synthesis of C-(E)-cinnamoyl glycosylic compounds as precursors for new biologically active C-glycosides

A series of beta-C-glycosylic ketones were prepared starting from d-glucose, d-xylose, d-mannose, and cellobiose. The beta-C-glycosylic ketones on aldol condensation with different aromatic aldehydes in the presence of a suitable organocatalyst led to the formation of respective C-(E)-cinnamoyl glycosides stereoselectively in good yields as precursors for the synthesis of biologically active compounds.

Synthetic studies in butenonyl C-glycosides: Preparation of polyfunctional alkanonyl glycosides and their enzyme inhibitory activity

A simple synthesis of phenyl butenoyl C-glycosides has been achieved by Aldol condensation of peracetylated glycosyl acetones with aromatic aldehydes followed by deacetylation with methanolic NaOMe. The selected butenoyl C-glycosides on conjugate addition of diethyl malonate resulted in polyfunctional alkanonyl glycosides in good yields. The butenoyl C- and alkanoyl C-glycosides were evaluated for their alpha-glucosidase, glucose-6-phosphatse and glycogen phosphorylase enzyme inhibitory activities in vitro. Three of the synthesized (3, 5 and 9) showed potent enzyme inhibitory activities as compared to standard drugs. Compounds 3, 5 and 9 were evaluated in vivo too displaying significant activity as compared to standard drugs acarbose and metformin.

A convenient synthesis of novel pyranosyl homo-C-nucleosides and their antidiabetic activities

A series of pyranosyl homo-C-nucleosides have been synthesized by reaction of butenonyl C-glycosides (5a-5j, and 8) and cyanoacetamide in presence of t-BuOK followed by further modifications. The reaction proceeds by Michael addition of cyanoacetamide to the butenonyl C-glycosides and subsequent dehydrative cyclization and oxidative aromatization to give glycosylmethyl pyridones (6a-6j, 7a-7j, 9, and 10). The glycosylmethyl pyridones (6a-6e) on reaction with POCl(3) under reflux gave respective glycosylmethyl pyridines (11a-11e and 12a-12e) in good yields. The synthesized compounds were screened for their in vitro α-glucosidase, glucose-6-phosphatase and glycogen phosphorylase inhibitory activities. One of the pyridylmethyl homo-C-nucleoside, compound 11d, displayed 52% inhibition of glucose-6-phosphatase as compared to the standard drug sodium orthovanadate while compound 12a showed a significant antihyperglycemic effect of 17.1% in the diabetic rats as compared to the standard drug metformin.

An efficient synthesis of tetramic acid derivatives with extended conjugation from L-Ascorbic Acid

Background Tetramic acids with polyenyl substituents are an important class of compounds in medicinal chemistry. Both solid and solution phase syntheses of such molecules have been reported recently. Thiolactomycin, a clinical candidate for treatment of tuberculosis has led to further explorations in this class. We have recently developed an efficient synthesis of tetramic acids derivatives from L- ascorbic acid. In continuation of this work, we have synthesised dienyl tetramic acid derivatives. Results 5,6-O-Isopropylidene-ascorbic acid on reaction with DBU led to the formation of tetronolactonyl allyl alcohol, which on oxidation with pyridinium chlorochromate gave the respective tetranolactonyl allylic aldehydes. Wittig olefination followed by reaction of the resulting tetranolactonyl dienyl esters with different amines resulted in the respective 5-hydroxy lactams. Subsequent dehydration of the hydroxy lactams with p-toluene sulphonic acid afforded the dienyl tetramic acid derivatives. All reactions were performed at ambient temperature and the yields are good. Conclusion An efficient and practical method for the synthesis of dienyl tetramic acid derivatives from inexpensive and easily accessible ascorbic acid has been developed. The compounds bear structural similarities to the tetramic acid based polyenic antibiotics and thus this method offers a new and short route for the synthesis of tetramic acid derivatives of biological significance.

Application of butenonyl-C-glucosides in the synthesis of pyrazolinyl-, aminopyrimidinyl- and biphenyl methyl-β-d-C-glucopyranosides

An access to different glycohybrids involving nucleophilic addition of N- and C-nucleophiles to the butenonyl glycosides followed by cyclization and subsequent reactions is reported. In the present communication, three different prototypes, β-d-glucopyranosylmethyl pyrazolines, β-d-glucopyranosylmethyl pyrimidines and β-d-glucopyranosylmethyl biphenyls, were prepared in moderate to good yields.Graphical Abstract