Synthesis of New Hexosaminyl D- and L-chiro-Inositols Related to Putative Insulin Mediators

We have developed an efficient synthetic strategy to HexNH2‐α(1⇄3)‐L‐chiro‐inositol (XII−XIII) and HexNH2‐α(1⇄2)‐D‐chiro‐inositol (XIV−XV) based on the regio and stereoselective glycosylation of tetrabenzoyl‐L‐chiro‐inositol 2 and tetrabenzyl‐D‐chiro‐inositol 14. Compounds XII−XV may constitute the central structural motifs of inositolphosphoglycans, which have been proposed as putative insulin mediators, and their syntheses have been designed on the basis of biosynthetic considerations. The syntheses of XII−XIII and XIV−XV involve the selective monoglycosylation of an L‐chiro inositol diequatorial diol system (2) and a D‐chiro inositol axial/equatorial diol system (14), respectively. To establish the experimental conditions to achieve the best reactivity−selectivity balance, the glycosylation reactions were studied using D‐gluco‐ and D‐galacto‐configured 2‐azido‐2‐deoxytrichloacetimidate glycosyl donors with different reactivities. The results obtained provide a practical synthetic route and new reactivity−selectivity data. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)