Stable, isotopically substituted carbohydrates: an improved synthesis of (6-13C)aldohexoses

1,2-O-Isopropylidene-alpha-D-xylo-pentodialdo-1,4-furanose (1) has been used as the parent aldose in the preparation of D-(6-13C)glucose and L-6-13C)idose via cyanohydrin reduction. The addition of K13CN (pH 6.8, 5 min) to 1 yields D-gluco and L-ido cyanohydrins that are readily reduced with H2 and Pd-BaSO4, to give 1,2-O-isopropylidene-alpha-D-gluco-hexodialdo-1,4-furanose (2; approximately 65%) and 1,2-O-isopropylidene-beta-L-ido-hexodialdo-1,4-furanose (3; 35%). Aldehydes 2 and 3 are reduced in situ with NaBH4, the resulting alcohols are deprotected with aqueous acid, and the aldoses are chromatographed on Dowex 50 X-8 (Ca2+) ion-exchange resin (200-400 mesh), to yield D-(6-13C)glucose (6) and L-(6-13C)idose (7). Molybdate epimerization of 6 and 7 yields D-(6-13C)mannose and L-(6-13C)gulose, respectively. A similar reaction scheme may be applied to methyl 2,3-O-isopropylidene-beta-D-ribo-pentodialdo-1,4-furanoside to generate the remaining four (6-13C)aldohexoses. This route is considerably simpler than the traditional Kiliani-Fischer route, and higher yields are obtained.