Spirocyclic penicillins

Abstract

The intramolecular, mercury-mediated cyclisation of (6S)-benzyl 6-[(R)-and (S)-2-amino-2-phenylacetamido]-6-(methylthio)penicillanates, (8) and (9), has been shown to give spiro[imidazolidine2,6′-penicillanate] derivatives. Unexpectedly, products (16) and (17), derived from attack on the morehindered β-face, were isolated in addition to the predicted products (10) and (11), formed by attack on the α-face. Formylation and removal of the carboxy protecting group gave spirocyclic penicillins devoid of useful antibacterial activity.