Derivatives of 6-aminopenicillanic acid. Part X. A non-enzymic conversion of benzylpenicillin into semi-synthetic penicillins

Abstract

The carboxy-group of penicillin G is conveniently protected by treatment of the derived ethoxyformic anhydride with (E)-benzaldehyde oxime or (E)-2-furaldehyde oxime. Treatment with phosphorus pentachloride and N-methylmorpholine, followed by methanol, then gives the corresponding O-(6-aminopenicillanoyl)oxime. After introduction of any desired N-acyl substituent the carboxy-protecting group is removed, as the corresponding nitrile, by mild treatment with a nucleophile in the presence of anhydrous base.