Abstract
A regioselective acylation series of methyl α-D-glucopyranoside (1), methyl 3-O-benzoyl-4,6-O-benzylidene-α-D-mannopyranoside (1A), and methyl 4,6-O-benzylidene-2-O-(3,5-dinitrobenzoyl)-α-D-mannopyranoside (1B) has been carried out by the direct acylation method and afforded the 2,6-di-O-glucopyranoside and 2 or 3-O-mannopyranoside derivatives in an excellent yield. In order to obtain newer products, the 2,6-di-O-glucopyranoside derivative was further transformed to a series of 3,4-di-O-acyl derivatives containing a wide variety of functionalities in a single molecular framework. The structures of the newly synthesized compounds were elucidated on the basis of IR, 1H-NMR, 13C-NMR, 13C-DEPT spectral data, and elemental analysis. These synthesized derivatives were screened for in vitro antimicrobial activities against ten human pathogenic and five phytopathogenic microorganisms. A number of test compounds showed remarkable antimicrobial activity comparable to, and in some cases even higher than, the standard antibiotics employed. It was observed that methyl 3,4-di-O-(3-chlorobenzoyl)-2,6-di-O-hexanoyl-α-D-glucopyranoside (8) exhibited a varied range of MIC from 12.5 μg/disc to 25 μg/disc by the disk diffusion method and 1000 μg/mL to 1250 μg/mL by the broth macrodilution method.
Highlights
Carbohydrate chemistry is found in the field of organic synthesis, protein and nucleic acid chemistry, enzymology, antibiotics, immunology, and biotechnology
It was observed that methyl 3,4-di-O-(3-chlorobenzoyl)-2,6-di-O-hexanoyl-α-D-glucopyranoside (8) exhibited a varied range of minimum inhibition concentration (MIC) from 12.5 μg/disc to 25 μg/disc by the disk diffusion method and 1000 μg/mL to 1250 μg/mL by the broth macrodilution method
As a continuation of a research project on the biological evaluation of carbohydrate derivatives and guided by some encouraging results obtained in this field [20,21,22], we deliberately synthesized some acylated derivatives of D-glucopyranoside (Scheme 1) and D-mannopyranoside (Scheme 2) containing a variety of substituents in a single molecular framework
Summary
Carbohydrate chemistry is found in the field of organic synthesis, protein and nucleic acid chemistry, enzymology, antibiotics, immunology, and biotechnology. Of the carbohydrates isolated from natural sources, acyl- and alkyl-glycoses or glycoside derivatives are important and some of these have effective biological activity [1,2,3]. The direct method has been considered by the carbohydrate chemists as one of the most effective for selective acylation of carbohydrates. Selective acylation is important because of its usefulness for the synthesis of biologically active carbohydrates [8,9,10] and nucleosides [11, 12]. The benzene and substituted benzene nuclei play an important role as the common denominator for various biological activities [16, 17]. We evaluated the antibacterial and antifungal activities of the synthesized compounds using various bacterial and fungal strains and the results are reported here for the first time
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