The fused@-lactam-thiazolidine structure proposed for penicillin has focused the attention of chemists on@-lactams. A recent discussion of the chemistry of P-lactains2 lists the compounds which had been prepared through 19-17, including those made during the collaborative British-American project on the chemistry of penicillin. No new methods for the synthesis of@-lactams were discovered in the course of the very intensive effort made to ...