Synthesis of allo- and epi-Inositol via the NHC-Catalyzed Carbocyclization of Carbohydrate-Derived Dialdehydes
摘要:
A synthesis of carbocyclic sugars from carbohydrate-derived dialdehydes using organocatalysis has been developed. Sorbitol, mannitol, and galactitol were converted via 1,6-tritylation, perbenzylation or permethylation, detritylation, and Swern oxidation into 2,3,4,5-tetra-O-alkyl-dialdoses that were cyclized via the benzoin reaction promoted by a triazolium carbene. Manno- and galacto-configured dialdehydes gave predominantly single inosose stereoisomers in up to 75% yield if the mixture was acetylated prior to isolation while the gluco-dialdehyde afforded a mixture of three stereoisomers in 61% overall yield. The inososes were stereospecifically reduced using sodium borohydride and then deprotected to give allo- and epi-inositol in good yield that confirmed the structural and stereochemical assignments.
Ruthenium Carbene Complexes with Imidazol-2-ylidene Ligands: Syntheses of Conduritol Derivatives Reveals Superior RCM Activity
作者:Lutz Ackermann、David El Tom、Alois Fürstner
DOI:10.1016/s0040-4020(99)01102-3
日期:2000.4
Syntheses of conduritol A, E and F derivatives are described using galactitol, d-mannitol and d-glucitol, respectively, as the starting materials. The key steps of this approach comprise a Tebbe olefination reaction for the preparation of dienes 15, 21 and 27 followed by ring closing metathesis (RCM) for the formation of the polyhydroxylated cyclohexene rings of the targets. A comparative study shows