Penicilloic acid degradation pathways

Fig. 5.7. The acid-catalyzed hydrolysis of penicillins involves first the formation of an acylium ion (5.22), which, by reacting with H20, yields penicil-loic acids 5.24 (Pathway b). The participation of a neighboring 6-acylamido group increases the rate of hydrolysis. During this intramolecular reaction (Pathway a), oxazolylthiazolidines (5.23) are formed and then give rise to the degradation products penicilloic acids 5.24, penicillenic acids 5.25,...

Scheme 19.17 Nucleophilic opening of penicillin s beta-lactam. This process occurs under basic conditions and is driven by the energetics associated with relieving the considerable bond-angle strain present in the 4-membered-ring. Two pathways are shown (i) The top results in acylation of a biological surface that has a good nucleophile such as the terminal amino-group on a lysine amino acid residue and, (ii) The lower represents a ready hydrolytic ring-opening by a water molecule to produce an inactive degradation product called penicilloic acid.

Study of the chemical degradation pathways of penicilloic acid (Levine 1960b,c Schwartz 1969) (see Fig. 5) suggested that penicilloic acid interacts with... 

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