- 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.
- King-Morris,Bondo,Mrowca,Serianni
-
-
- HYDROXIDE-CATALYZED ISOMERIZATION OF D-(1-13C)MANNOSE: EVIDENCE FOR THE INVOLVEMENT OF 3,4-ENEDIOLS
-
The KOH-catalyzed isomerization of D-(1-13C)mannose under anaerobic conditions was studied by 13C-n.m.r. spectroscopy.D-(1-13C)Glucose and D-(1-13C)fructose are generated during the reaction, as expected.In addition, however, (6-13C)glucose, (6-13C)mannose, and (6-13C)fructose are produced in small proportions, possibly via symmetrical 3,4-enediol intermediates.The involvement of the latter structures in 13C-label shifting is inferred from the observation of (1-13C)sorbose and (6-13C)sorbose in the reaction mixture.
- King-Morris, Melinda J.,Serianni, Anthony S.
-
-