Sulfur-Free Penicillin Derivatives. V. Preparation, Hydrolysis, and Oxidative Rearrangement Of Fused Oxazoline–Azetidinones

Author:

Wolfe Saul,Lee Shui-Lung,Ducep Jean-Bernard,Kannengiesser Gérard,Lee Wha Suk

Abstract

Chlorinolysis of an anhydropenicillin affords a 2-(2′-chloro-3′S-amino, -acylamino or -phthalimido-4′-oxo)azetidinyl-3-methyl-2-butenoyl chloride, as a mixture of 2′R (cis) and 2′S (trans) epimers in which the 2′R epimer usually predominates. Hydrolysis of the acid chloride and treatment of the carboxylic acid with aqueous bicarbonate causes cyclization, in the case of a 3′-acylamino substituent, to a 2R-6-(1′-carboxy-2′-methyl-prop-1-enyl)-1-oxa-3,6-diaza-4S,5R-bicyclo[3,2,0]hept-2-ene-7-one. The mechanisms of these transformations are discussed, and alternative routes to such fused oxazoline–azetidinones are also presented.The oxazolines undergo ready hydrolysis to sulfonic acid salts of 2-(2′R-acyloxy-3′S-amino-4′-oxo)azetidinyl-3-methyl-2-butenoates upon treatment with the hydrate of a sulfonic acid in acetone solvent. Neutralization of these salts proceeds without O → N acyl transfer, because acylation yields a diacylated azetidinone in which the new acyl substituent is attached to nitrogen. Monobromination of the allylic methyl groups of these salts, followed by treatment with 2 molar-equiv. of triethylamine, leads to a deep-seated rearrangement, in high yield, to an oxazinone. The mechanism of this rearrangement and, in particular, the role of acylimines in this and related reactions, including the biosynthesis of penicillin, are discussed.

Publisher

Canadian Science Publishing

Subject

Organic Chemistry,General Chemistry,Catalysis

Cited by 17 articles. 订阅此论文施引文献 订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献

1. Tetramethylguanidinium Azide;Encyclopedia of Reagents for Organic Synthesis;2004-10-15

2. An unprecedented cleavage of the β-lactam ring: a novel synthesis of acyclic N,O- and N,S-acetals;J. Chem. Soc., Perkin Trans. 1;1996

3. 1992 Lemieux Award Lecture Studies related to the penicillin receptor;Canadian Journal of Chemistry;1994-04-01

4. Synthesis of 4-Substituted Monocyclic β-Lactams by a Lewis Acid-mediated Reaction;Agricultural and Biological Chemistry;1986-04

5. STUDIES RELATED TO BETA-LACTAM COMPOUNDS;Current Trends in Organic Synthesis;1983

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