Studies related to penicillins. Part XI. Mechanism of degradation of benzylpenicillinic and phenoxymethylpenicillinic acid by mercury(II) acetate

Abstract

Acetoxymercury(II)(2S)-3-acetoxymercurio(II)thio-2-{(1R,5S)-3-benzyl-6-oxo-2-oxa-4,7-diazabicyclo[3.2.0]-hept-3-en-7-yl}-3-methylbutanoate (16) is formed when potassium benzylpenicillinate (1) is added to mercury(II) acetate in acetic acid. The salt (16) is converted into (3S, 4S)-4-acetoxy-1-(2-methylprop-1-enyl)-3-phenylacetamidoazetidin-2-one (6) by hot acetic acid, into (1R,5S)-3-benzyl-7-(2-methylprop-1-enyl)-2-oxa-4,7-diazabicyclo[3.2.0]hept-3-en-6-one (10) by dimethyl sulphoxide, and into methyl (2S)-2-{(1R,5S)-3-benzyl-6-oxo-2-oxa-4,7-diazabicyclo[3.2.0]hept-3-en-7-yl}-3-mercapto-3-methylbutanoate (15) by diazomethane. Pyridine removes the elements of mercury(II) acetate from the salt (16) to give the derivative (21).

Potassium phenoxymethylpenicillinate (2) undergoes an analogous reaction in the presence of mercury(II) acetate and acetic acid to give the salt (18). This derivative is also converted into the acetate (7) by hot acetic acid, into the methylpropenyl derivative (12) by dimethyl sulphoxide, into the ester (17) by diazomethane, and into the salt (22) by pyridine.