A new process is described for the preparation of (5R)-penem derivatives of the general formula I: ##STR1## wherein R.sub.1 represents a hydrogen atom or an organic group; R.sub.2 represents a hydrogen atom or a carboxy protecting group and Y represents a hydrogen or halogen atom or an organic group. A 2-thiacephem derivative of the general formula II: ##STR2## wherein R.sub.1, R.sub.2 and Y have the meanings/given above is oxidized by means of organic peracids to the corresponding sulphone of the general formula III: ##STR3## which is subsequently submitted to a desulphurative ring contraction by extrusion of SO.sub.2 to give exclusively the desired (5R)-penem derivatives of the general formula I.
Compounds of formula
wherein R, and R, is each H, halo or an organic group, R3 is H or organic group, n = 1 or 2, M is a heavy mono- or divalent metal, or M2A wherein M2 is a heavy divalent metal and A is an organic or inorganic group, are prepared by treating a starting penicillin in a solvent with a salt of M, or M2A in the presence of a base at a temperature of from --70° to 100°C. The azetidinones of formula I are useful intermediates in the synthesis of β-lactam antibiotics, esp penem.
式 I 的氮杂环丁酮化合物是合成 β-内酰胺类抗生素(尤其是青霉烯)的有用中间体,其中 R 和 R 分别为 H、卤素或有机基团,R3 为 H 或有机基团,n = 1 或 2,M 为一价或二价重金属,或 M2A,其中 M2 为二价重金属,A 为有机或无机基团。
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作者:ALPEGIANI M.、 BEDESCHI A.、 FOGLIO M.、 FRANCESCHI G.、 PERRONE E.