Dale et al. discussed the role of the hydroxyl groups in the interaction of sugars with the /3-glucosidase by investigating the inhibitory effects of some monosaccharides and their derivatives against the enzyme [1]. We planned to investigate the role of glycon hydroxyl groups via a kinetic study on the hydrolysis of deoxymonosaccharide-containing substrates by glycosidases. In our program, simple and efficient syntheses of various deoxymonosaccharides was required. In this report, a convenient synthesis of deoxy derivatives of D-mannose, namely D-rhamnose (6-deoxy-D-mannose, 7), 4-deoxy-Dlyxo-hexose (" 4-deoxy-D-mannose", 8), and 4,6-dideoxy-D-lyxo-hexose ("4,6-dideoxy-D-mannose", 9), is described. Several reports have been published on the synthesis of D-rhamnose [2-5] and 4-deoxy-D-lyxo-hexose [6-10]; however, there is no report on the synthesis of 4,6-dideoxy-D-lyxo-hexose.
Methyl 2,3-O-isopropylidene-6-O-(p-tolylsulfonyl)-a-D-mannopyranoside (1), available in two steps from methyl a-o-mannopyranoside [11,12], was the common intermediate for the synthesis of these three deoxy monosaccharides. The p-tolylsulfonyl group is useful for the protection and the deoxgenation of the C-6 hydroxyl group of 1; thus treatment with sodium borohydride in hot dimethyl sulfoxide gave a deoxygenated product, methyl 2,3-O-isopropylidene-a-D-rhamnopyranoside 2. Similarly, Fang et al. produced 2 from 1 using lithium aluminum hydride as a reducing agent [12].