Vitamin B12-catalyzed synthesis of some peracetylated alkyl b-D-xylopyranosides

Abstract

The vitamin B12-catalyzed glycosylation reaction of brominated b-D-xylose peracetate with alkanols ROH (C1-C8) has been studied. The catalytically active species in this reaction was cob(I)alamin, obtained by chemical reduction of Vitamin B12 with NaBH4 (Co(III) to Co(I)). The reaction was carried out with 2 mol% of vitamin B12, with respect to xylosyl bromide 1, under argon at room temperature. Under these conditions, peracetylated C1-C8-alkyl b-D-xylopyranosides (3a–3f) were obtained in moderate yield (55–70 %). In all cases 3,4-di-O-acetyl-D-xylal (4) was obtained, as the product of reductive elimination of peracetylated xylosyl bromide (15–25 %).

Keywords

• alkyl b-D-xylopyranosides
• brominated b-D-xylose peracetate
• glycosylaton
• vitamin B12