The use of carbonyl group anisotropy effect in determination of the relative configuration of carbapenams

Abstract

Assignments of relative configuration of the newly formed stereogenic center at the bridgehead carbon atom of bicyclic carbapenams obtained in Kinugasa reaction can be easily achieved by analyzing chemical shifts of the H-2 proton and geminal protons of the protected alkoxymethyl group at the C-2 carbon atom. The differences of 1H NMR chemical shifts of these protons fall in two ranges of about 3.3-3.7 ppm, and 4.0-4.4 ppm. This observation can be attributed to the influence of the anisotropy of the neighboring carbonyl group and can be easily correlated with configuration at the bridgehead carbon atom. © ARKAT-USA, Inc.