Ashok K. Yadav

Synthesis of some new pyrido[2,3‐d]pyrimidines and their ribofuranosides as possible antimicrobial agents

The ribofuranosides, namely, 4-amino-5,7-disubstituted-1-[2′,3′,5′-tri-O-benzoyl-α-d-ribofuranosyl]pyrido-[2,3-d] pyrimidine-2(1H)-thiones, have been synthesized by the condensation of trimethylsilyl derivatives of 5,7-disubstituted pyrido[2,3-d]pyrimidine-2(1H)-thiones with β-d-ribofuranose-1-acetate-2,3,5-tribenzoate in the presence of SnCl4. The heterocyclic bases, namely, 4-amino-5,7-disubstituted pyrido[2,3-d]pyrimidine-2(1H)-thiones, were synthesized by the treatment of 2-amino-3-cyano-4,6-disubstituted pyridines with thiourea. The structures of all the synthesized ribofuranosides and their precursors have been established by elemental analysis, IR, and 1H NMR spectral data. The 13C NMR data of ribofuranosides has also been presented. All the synthesized heterocyclic bases and their ribofuranosides have been screened for their antibacterial and antifungal activities.

Bioengineered probiotics as a new hope for health and diseases: an overview of potential and prospects.

Despite the use of microorganisms as therapeutics for over a century, the scientific and clinical admiration of their potential is a recent phenomenon. Genome sequencing and genetic engineering has enabled researchers to develop novel strategies, such as bioengineered probiotics or pharmabiotics, which may become a therapeutic strategy. Bioengineered probiotics with multiple immunogenic or antagonistic properties could be a viable option to improve human health. The bacteria are tailored to deliver drugs, therapeutic proteins or gene therapy vectors with precision and a higher degree of site specificity than conventional drug administration regimes. This article provides an overview of methodological concepts, thereby encouraging research and interest in this topic, with the ultimate goal of using designer probiotics as therapeutics in clinical practice.

Facile Ionic Liquid–Mediated Protocol for the Regioselective Synthesis of 1,5-Benzothiazepines

Abstract An efficient one-step ionic liquid–mediated green protocol for the regioselective synthesis of (+)/(±)-cis-2-(4-methoxy/benzyloxyphenyl)-3-hydroxy-2,3-dihydro-1,5-benzothiazepin-4-[5H]-ones has been developed from the reaction between substituted 2-aminobenzenethiol and methyl-(±)-trans-3-(4-methoxy/benzyloxy phenyl)glycidate, under nitrogen atmosphere, at 60 ± 2 °C. The reaction has been performed in ionic liquids (viz, 1-butyl-3-methylimidazolium bromide/hexafluorophosphate), and the yields of the 1,5-benzothiazepine derivatives were found to be excellent. The cis-stereoisomer was obtained as the major product along with a trans-isomer as minor product.

Enantioselective cathodic reduction of some prochiral ketones in the presence of (-)-N, N'-dimethylquininium tetrafluoroborate at mercury cathode

Abstract This work describes preparative scale enantioselective cathodic reduction of some prochiral ketones, viz. 3,4-dihydro-1(2 H )-naphthaleneone, 2-octanone, 1-phenyl-2-propanone, E -3-octen-2-one, 1-octyn-3-one, 1-undecyn-3-one, 1-tetradecyn-3-one at mercury pool in N , N -dimethyl formamide (DMF)–2-propanol (9.5:0.5), using tetrabutylammonium tetrafluoroborate (TBA·BF 4 ), as supporting electrolyte and (−)- N , N ′-dimethylquininium tetrafluoroborate (DMQ·2BF 4 ), as a enantioselective inductor. The products obtained were corresponding ( S )-alcohols in 24–70% ee.

Synthesis of Some Novel 4-Imino-3,5,7-Trisubstituted Pyrido[2,3-d]Pyrimidine-2(1H)-Thiones and Their Nucleosides as Potential Therapeutic Agents

Abstract Some newer 4-imino-3,5,7-trisubstituted pyrido[2,3-d]pyrimidine-2(1H)-thiones were synthesized by the condensation of 2-amino-3-cyano-4,6-disubstituted pyridines with phenylisothiocyanate. The nucleosides viz., 4-imino-3,5,7-trisubstituted-1-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)pyrido[2,3,-d]pyrimidine-2(1H)-thiones were synthesized by the condensation of trimethylsilyl derivatives of pyrido[2,3-d]pyrimidine with sugar namely β-D-ribofuranose 1-acetare-2,3,5-tribenzonte while 4-imino-3,5,7-trisubstituted-1-(2,3,5-tri-O-benzoyl-α-D-ribofuranosyl)pyrido(2,3-d]pyrimidine-2(1H)-thiones were prepared by condensing trimethylsilyl derivatives of pyrido[2,3-d]-pyrimidine with sugar in presence of SnCl4. All the synthesized nucleosides and their precursors were characterized by spectral and elemental analysis data and have been screened for their antimicrobial activities.

Synthesis and antimicrobial screening of some new 4-imino-3,5,7-trisubstituted pyrido[2,3-d]pyrimidines and their ribofuranosides as potential chemotherapeutic agents

Some new nucleosides, viz. 4-imino-3,5,7-trisubstituted-1-(2′,3′,5′-tri-O-kbenzyl–β-D-ribofuranosyl)pyrido[2,3-d]pyrimidin/e–2(1H)-ones/ thiones(VII/VIII), have been synthesized by condensation of trimethylsilyl derivatives of 4-imino-3,5,7-trisubstituted pyrido[2,3-d]pyrimidin/e-2(1H)-ones/thiones (III/IV) with β-D-ribofuranosyl1-acetate-2,3,5-tribenzoate. Compounds III/IV have been synthesized by refluxing 2-amino-3-cyano-4,6-disubstituted pyridine (II) with substituted an arylisocyanate or an isothiocyanate respectively. The structure of all the synthesized compounds have been established by IR and 1H NMR studies. These compounds have been screened for antimicrobial activities in order evaluate. The possibility of the derivatives to be used as potential chemotherapeutic agents.

SYNTHESIS OF SOME 2-THIOXOPYRIDO[2,3-d]PYRIMIDINE RIBOFURANOSIDES AND THEIR ANTIMICROBIAL ACTIVITY

Abstract 2-Thioxc-3,5,7-trisubstitutcd-I-[2′.3′,5′-tri-O-benzoyl-β-D-ribofuranosyllpyrido [2,3-d]pyri midin-4(IH)-ones have been prepared by the condensation of trimethylsilyl derivative of 2-thioxo-3,5,7-trisubstituted pyrido[2,3-d]pyrimidin-4(IH)-ones with β-D-ribofuranose 1-acetate-2,3,5-tribenzoate in 65%-78% yield. The structure of the synthesized ribofuranosides and their precursors have been established by IR, 1H NMR and elemental analysis. These derivatives have been screened for their antimicrobial activity.

SYNTHESIS OF NOVEL THIOXODERIVATIVES OF PYRIDO[2,3-d]PYRIMIDINES AND THEIR NUCLEOSIDES AS POSSIBLE ANTICANCER AGENTS

Abstract Synthesis of some 2-thioxo-3,5,7-trisubstituted pyrido[2,3-d]pyrimidine-4(1H)-ones and corresponding nucleosides viz. 2-thioxo-3,5,7-trisubstituted-1-(2,3,5-tri-O-benzoyl-β-D-ribofuranosyl)pyrido[2,3-d]-pyrimidine4 (1H)-ones is reported. The results of antimicrobial activities are also reported. The structures of the compounds have been established by elemental, IR and NMR analyses.

Anodic oxidations—I. The Kolbe oxidation of unsymmetrical half-esters derived from stobbe condensation

Abstract The Kolbe oxidation of some partially neutralized half-ester, viz., 3-carbethoxy-4,4-diphenyl but-3-enoic acid ( 1 ), 3-carbethoxy-4,4-dimethyl but-3-enoic acid ( 2 ), 3-carbethoxy-3-cyclopent-1′-en-propionic acid ( 3 ) and 3-carbethoxy-3-cyclohex-1′-en-propionic acid ( 4 ), has been investigated in an undivided cell at smooth platinum foil anode in methanol. In order to optimize the yield of the dimer, the anodic oxidation of 1 has been studied in detail by varying different parameters, like current density, degree of partial neutralization of the half-ester and electrode material. Besides the dimerized product, affoded by all these half-ester, two stereoisometric ethers, viz., ethyl 2-methoxymethyl-3,3-diphenyl prop-2-enoate ( 1b ) and ethyl 2-[methoxy (diphenyl)] methyl prop-2-enoate ( 1c ) have been isolated in 69% and 11% respectively from 1 in a typical experiment. The probable mechanism for the process has been presented.