Thiazolidine Ring Opening in Penicillin Derivatives. Part 2. Enamine Formation

Andrew M. Davis, Nicola J. Layland, Michael I. Page, Frances Martin, Rory More O’ferrall

Research output: Contribution to journalArticlepeer-review

16 Citations (Scopus)


The alkaline hydrolysis of (3S,5R,6R)-methyl benzylpenicilloate, and the corresponding carboxamide and N-ethylamide, is accompanied by an absorbance increase at 285 nm. This is attributed to a competing elimination reaction across C6–C5 to open the thiazolidine ring and reversibly generate an enamine intermediate. Kinetic analysis and hydrolysis in D2O do not indicate a significant buildup of this intermediate during hydrolysis of the methyl ester. However, over the pH range 4–11 the rate of thiazolidine ring opening is competitive with hydrolysis of the ester function. The deuterium solvent kinetic isotope effect on the ring closure reaction is 7.5.

Original languageEnglish
Pages (from-to)1225-1229
Number of pages5
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number8
Publication statusPublished - Aug 1991


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