Selective Anomeric Deacetylation of Per-Acetylated Carbohydrates Using (i-Pr)3Sn(OEt) and Synthesis of New Derivatives

In this study natural carbohydrates such as glucose, galactose, xylose, fructose andlactose, are acetylated by acetic anhydride and sodium acetate catalyst. Anomeric configuration is deacetylated by (i-Pr)3Sn(OEt)as a catalyst, an easy synthetic regioselective deacetylation of full acetylated carbohydrates using (i--Pr)3Sn(OEt) is described. The acetylated carbohydrates reacted with HBr (solution in AcOH, 32 wt.%) for the bromination of anomeric position. The synthesis oxazaphosphorine, and bromo hexa alkyl Methylsulfonate derivatives from anomeric position of carbohydrates was reacted. FT IR, 1H, 13C NMR, 31PNMR spectroscopy techniques were employed to examine the synthesized compounds.

Synthesis of various β-D-glucopyranosyl and β-D-xylopyranosyl hydroxybenzoates and evaluation of their antioxidant activities

Various β-D-glucopyranosyl and β-D-xylopyranosyl hydroxybenzoates were efficiently prepared from 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide (TAGB) or 2,3,4-tri-O-acetyl-α-D-xylopyranosyl bromide (TAXB), respectively, by amine-promoted glycosylation. Regioselective deacetylation of the resulting acetylated β-D-gluco- and β-D-xylopyranosyl hydroxybenzoates was investigated using Novozym 435 as a lipase catalyst. In the case of β-D-glucopyranosyl hydroxybenzoates, Novozym 435-catalyzed deacetylation is regioselective at C-4 and C-6 positions. On the other hand, β-D-xylopyranosyl hydroxybenzoates are deacetylated only at the C-4 position. Antioxidant activities of free hydroxybenzoic acids and the respective β-D-gluco- and β-D-xylopyranosyl hydroxybenzoates were evaluated by DPPH˙ radical scavenging as well as their inhibitory effect on autoxidation of bulk methyl linoleate. The β-D-xylopyranosyl protocatechoate, as well as quercetin and α-tochopherol, show high antioxidant activity for the radical scavenging activity by 1,1-diphenyl-2-picrylhydrazyl (DPPH˙). In bulk methyl linoleate, the antioxidant activities of β-D-gluco- and β-D-xylopyranosyl protocatechoates are higher than that of α-tocopherol.