A preparation of protected 2-deoxy-2-hydroxymethyl-d-mannose and -d-glucose derivatives not involving organometallic reagents

The branched chain protected sugar, 2-C-hydroxymethyl-2,3;5,6-di-O-isopropylidene-d-mannofuranose was specifically benzylated at the primary hydroxyl group position by the stannylene procedure (93%). Oxidation with pyridinium chlorochromate gave in 71% yield 2-C-benzyloxymethyl-2,3;5,6-di-O-isopropylidene-d-mannonolactone which was reduced with 3 equiv of samarium diiodide in oxolane to a 56:44 mixture of the 2-deoxy derivatives, 2-C-benzyloxymethyl-2-deoxy-5,6-O-isopropylidene-d-mannono- (5) and -d-glucono-lactones in 83% combined yield. Reduction of lactone 5 with DIBAH in dichloromethane gave the protected branched chain sugar, 2-C-benzyloxy-2-deoxy-5,6-O-isopropylidene-d-mannose in 63% yield. In the reduction of 2-C-hydroxymethyl-2,3;5,6-di-O-isopropylidene-d-mannonolactone and 2-C-hydroxymethyl-d-mannonolactone in water solution, only lactones with the d-manno configuration, 2-deoxy-2-C-hydroxymethyl-5,6-O-isopropylidene-d-mannonolactone and 2-deoxy-2-C-hydroxymethyl-d-mannono-(1,5)-lactone, could be isolated or characterized among the products of the reaction.