Asymmetric induction in [2+2]cycloaddition of chlorosulfonyl isocyanate to

Abstract

The asymmetric [2+2]cycloaddition of chlorosulfonyl isocyanate to 1,2-O-isopropylidene-5-O-vinyl-d-glycofuranoses is presented. The stereoselectivity strongly depends on substitution and configuration at the C-3 carbon atom. A small substituent at C-3 or allo configuration of the sugar promote excellent stereoselectivity, affording (S) configuration at the C-4′ carbon atom of the azetidinone ring. Intramolecular cyclization in compounds 20, 22–26, and 31 provides the respective clavams 32–38.