Stereocontrolled synthesis of 1-oxabicyclic β-lactam antibiotics via[2 + 2]cycloaddition of isocyanates to sugar vinyl ethers

Abstract

[2 + 2]Cycloaddition of chlorosulfonyl and trichloroacetyl isocyanates to sugar vinyl ethers affords the corresponding azetidin-2-ones in moderate to good yields. Diastereofacial differentiation in these reactions is sterically dependent and usually provides excellent configuration control at C-4 of the azetidin-2-one ring. Deprotection of the amide nitrogen in those adducts, followed by suitable transformations of the sugar part, enables construction of a variety of β-lactam structures.