Evidence for Stereoelectronic Control in the OsO_4 Bis-hydroxylation of tran8-Cyclohex-2-ene-1,4-diol8. Synthesis of Differentially Protected myo-Inositol Derivatives

摘要

The importance of osmium tetraoxide-catalyzed cis-dihydroxylation of olefins is evident for the consideration of its use in the stereoselective synthesis of polyhydrox-ylated compounds. In the case of the oxidation of allylic-substituted alkenes the origin of the diastereoselection can be attributed to steric, Stereoelectronic, and con-formational4 effects. From the studies performed by Kishi, an empiric rule established that osmylation of 1,2-disubstituted acyclic and cyclic olefins containing an allylic oxygen-bearing stereocenter affords diols with a stereochemically predictable outcome with the major product being the one arising from the anti attack to the oxygen function. If the change of the electronic properties of a stereogenic center controls the diastereoselectivity in the OsO_2 attack, this powerful tool should be employed in organic synthesis. In this context we have previously described short and efficient, syntheses of the myo-inositol derivative 2a and of the aminocyclitol moiety of the antibiotic hygromycin A (2b) from 7-oxanorbornenes (Scheme 1).