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Paper | Regular issue | Vol 38, No. 4, 1994, pp.843-851
Published online, 1st January, 1970
DOI: 10.3987/COM-93-6652
From Penicillins to 4,5-Dioxothiazolidines: A Thermal Rearrangement of Tritylaminopenam Derivatives

Marco Alpegiani and Ettore Perrone*

*Pharmacia Farmitalia Carlo Erba Srl, 20014 Nerviano, Milano, Italy

Abstract

Thermolysis of p-nitrobenzyl 6β-tritylaminopenicillanate 1β-oxide (1) afforded (2R)-3-methyl-2-(4-oxo-5-tritylimino-3-thiazolidinyl)-3-butenoate (8), which could be easily converted into 4,5-dioxothiazolidines (9, 11). The influence of catalytic amounts of 2-mercaptobenzothiazole in promoting the rearrangement, and the isolation of the thiazolidinone (10) from thermolysis of a model azetidinone (17), suggest that the unusual scission of the C-5,C-6 bond originally present in penam (1) occurred at the level of tritylamino-1,2-secopenicillanates. A mechanism is proposed after the observation that the 6α-deuteriated penam (2) rearranged to the undeuteriated thiazolidinone (8), whilst epimeric 2-deuterio derivatives (18) were produced from 1 in the presence of D2O.