Stereoselective Michael addition reactions of 5-glyco-4-nitrocyclohex-1-enes

Abstract Michael additions of 5-glyco-4-nitrocyclohex-1-enes ( 2 and 3 ) proceeded in a stereoselective way, leading in each case to single adducts in which the electron-deficient alkenes add on the C-4 of the cyclohexene rings, in a trans mode to the adjacent, sterically demanding, sugar side-chain. When dimethyl maleate or dimethyl fumarate and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were used, there was in situ elimination of nitrous acid, and the product consisted in a 1:1 mixture of the epimeric α,β-unsaturated esters 7 .