OPTICALLY-ACTIVE QUATERNARY CARBON CENTERS FROM THE PHOTOADDITION OF CHROMIUM ALKOXYCARBENE COMPLEXES AND OPTICALLY-ACTIVE THIAZOLINES

The photolytic reaction of chromium-alkoxycarbene complexes with valine-derived, optically active thiazolines produced optically active beta-lactam penam derivatives in fair to good yield and with high diastereoselectivity. In most cases alcoholosis of the beta-lactam followed by solvolysis of the thiazolidine ring produced optically active quaternary centers having carbon substituents in four different oxidation states-alkane, alkoxy, aldehyde, and ester. The absolute configuration of the stereogenic center could be inverted by a sequence of redox manipulations of the ester and aldehyde group, making either enantiomer available from the same precursor.