Sugars branched-chain, cyclic acetals

Stereodivergent pathways relative to other allylic systems (e.g. allylic acetates) have been found in the reactions of cyclic allylic sulfides or ethers of benzothiazole with organocopper reagents. In this case the Sn2 process occurs with syn stereochemistry (eq 5) and is due to the anchimeric coordination of the organometallic reagent with the heterocyclic moiety. This has been utilized for regio- and stereocontroUed access to branched-chain sugars. 

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