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

1,2- O-Isopropylidene-α- 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 K 13CN (pH 6.8, 5 min) to 1 yields d- gluco and l- ido cyanohydrins that are readily reduced with H 2 and Pd-BaSO 4, to give 1,2- O-isopropylidene-α- d- gluco-hexodialdo-1,4-furanose ( 2; ∼65%) and 1,2- O-isopropylidene-β- dl- ido-hexodialdo-1,4-furanose ( 3; 35%). Aldehydes 2 and 3 are reduced in situ with NaBH 4, the resulting alcohols are deprotected with aqueous acid, and the aldoses are chromatographed on Dowex 50 X-8 (Ca 2+) 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-β- 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.