Md. Musawwer Khan

Bicyclic Hybrid Sugars as Glycosidase Inhibitors: Synthesis and Comparative Study of Inhibitory Activities of Fused Oxa-Oxa, Oxa-Aza, and Oxa-Carbasugar Hybrid Molecules

A few bicyclic hybrid sugar molecules comprising of oxa-aza, oxa-oxa, and oxa-carbasugar fused skeletons were designed and synthesized from C-2 acetoxyglucal involving Ferrier rearrangement, Grignard addition, and ring-closing metathesis as key steps. The inhibitory activities of the synthesized molecules were tested against commercially available enzymes, which revealed the sugar-piperidine and sugar-pyran hybrids as potent and selective inhibitors.

A simple and convenient synthetic protocol for O-isopropylidenation of sugars using bromodimethylsulfonium bromide (BDMS) as a catalyst.

Various O-isopropylidene derivatives of sugars and acyclic sugars were obtained in very good yields on reaction with acetone at room temperature with a catalytic amount of bromodimethylsulfonium bromide (BDMS). These O-isopropylidene derivatives can also be prepared in good yields on reaction with 2,2-dimethoxypropane (DMP) in acetonitrile using the same catalyst in shorter reaction times. Some of the advantages of this method are high effectiveness, a nonaqueous workup procedure, economic viability, and good yields.

Recent advances in multicomponent reactions involving carbohydrates

Being an attractive class of naturally occurring molecules with fascinating properties sugars and their derivatives have wide applications in different fields especially in drug discovery. Due to their highly diverse nature they play various important key roles in biological systems. In terms of providing both desirable structural diversity and compound libraries, multicomponent reactions (MCRs) are most efficient strategies. MCRs are widely employed by chemists to generate sugar based derivatives with significantly extended variations having various benefits to society. The advances in the synthesis of structurally diversified sugar based derivatives through new MCRs of the previous decade are reviewed.

Tetrabutylammonium tribromide (TBATB): a mild and efficient catalyst for O-isopropylidenation of carbohydrates

A wide range of O-isopropylidene derivatives can be prepared from the sugars and their derivatives on reaction with acetone at room temperature by employing 2 mol% of tetrabutylammonium tribromide (TBATB) as a catalyst. Good yields, low catalyst loading, mild reaction conditions, and a non-aqueous workup procedure are some major advantages of this protocol.

Synthesis of functionalized dihydro-2-oxypyrroles and tetrahydropyridines using 2,6-pyridinedicarboxylic acid as an efficient and mild organocatalyst

Simple and efficient protocols have been developed for the synthesis of diversely functionalized dihydro-2-oxypyrroles and tetrahydropyridines. One-pot four-component reaction of dialkyl acetylenedicarboxylates, amines and formaldehyde in the presence of 2,6-pyridinedicarboxylic acid in methanol at room temperature provides dihydro-2-oxypyrroles. The combination of β-ketoesters, aromatic aldehydes and amines yielded tetrahydropyridine derivatives under the same reaction conditions. The salient features of these methods are mild reaction conditions, reduced reaction time, moderate to high yields, applicability to a broad range of substrates and no tedious column chromatographic separation.

Bromodimethylsulfonium bromide (BDMS) mediated dithioacetalization of carbohydrates under solvent-free conditions.

A variety of diethyl dithioacetals of sugars can be prepared in very good yields by the reaction of various monosaccharides with ethanethiol in the presence of 3 mol% bromodimethylsulfonium bromide (BDMS) at 0-5°C. Similarly, dipropyl dithioacetal derivatives can also be obtained in good yields using propanethiol under identical reaction conditions. These dithioacetal derivatives were characterized by per-O-acetylation using silica gel-supported perchloric acid. The significant features of the present protocol are good-to-excellent yields, mild, clean, and solvent-free reaction conditions. This method is extremely suitable for the large-scale preparation of dithioacetal derivatives of various sugars.

Recent developments in multicomponent synthesis of structurally diversified tetrahydropyridines

Tetrahydropyridines (THPDs) have been recognized as a major constituent of naturally occurring alkaloids. Being heterocyclic nitrogenous compounds, they therefore display robust biological and pharmacological profiles. In this context, they are fascinating synthetic targets in synthetic chemistry and as a consequence of this their synthesis through simple and convenient tactics has emerged as an important and challenging task. To meet such challenge, multicomponent reactions (MCRs) are employed as an excellent tool for achieving compounds containing complex diversity in single step and production of their vast libraries. This review represents the advancement made in the field of multicomponent synthesis of THPDs and their derivatives of the last few years.

VO(acac)2/H2O2/NaI: a mild and efficient combination for the cleavage of dithioacetal derivatives of sugars

A wide variety of dithioacetal derivatives of sugars can be cleaved easily into the corresponding open-chain aldehydo sugars using an efficient combination of VO(acac)(2)/H(2)O(2)/NaI at 0-5°C. Some of the salient features of this protocol are mild reaction conditions, good yields, short reaction times, easy work-up procedures, and non-involvement of toxic chemicals.

One-pot practical method for synthesis of functionalized 4H-chromen-5-one derivatives under catalyst and solvent-free conditions

Abstract A facile and practical method was described for the synthesis of 4H-chromen-5-ones under catalyst- and solvent-free conditions by one-pot stirring of starting materials at 110 °C. The products were obtained by the reaction between cyclic 1,3-dicarbonyl compounds, aromatic aldehydes and (E)-N-methyl-1-(methylthio)-2-nitroethenamine (NMSM) in short duration with good to excellent yields. This simple and environmentally benign method eliminates the use of expensive, metallic and corrosive catalysts, hazardous organic solvents, and chromatographic separation. GRAPHICAL ABSTRACT