Transformations of penicillin. Part II. NN′-Di-isopropyihylrazine, a new reagent for protection of carboxylic acids

Abstract

NN′-Di-isopropylhydrazine is a useful reagent for the protection of carboxylic acids. The derived hydrazides can be reconverted by selective oxidation, with, for example, lead tetra-acetate, into the parent acids in very high yield. The protecting group has been used for penicillins. Acid-catalysed rearrangement of the NN′-di-isopropyl-hydrazide from 6β-phenylacetamidopenicillanic acid (S)-sulphoxide, followed by oxidative cleavage of the protecting group, afforded the corresponding deacetoxycephalosporanic acid. Thermal rearrangement of the N-iso-propylhydrazide of 6β-phenylacetamidopenicillanic acid (S)-sulphoxide gave a moderate yield of anhydropenicillin.