Benzylpenilloic acid

The following trivial names have been assigned to the penicillin transformation products shown (6), benzylpenicilloate (7), benzylpenaldic acid (8), D-penicillamine (9), a-methyl D-a-benzylpenicilloate (10), benzylpenillic acid (11), benzylpenillamine (12), benzyl-isopenillic acid (13), benzylpenilloic acid (14), benzylpenilloaldehyde (15), benzylpenicil-lenic acid (16) benzylpenillonic acid methyl ester and (17), dethiobenzylpenicillin methyl ester. 

Spectra of benzylpenilloic acids (see Figure 5.36) are more complex than those of the penicilloic acids as a result of the non-equivalence of the methylene protons produced at C-6 after decarboxylation. Full analysis is possible, however, from a 400 MHz spectrum, which reveals four 2-methyl resonances and duplicate 3-H, PhCH2, 5-H and fi-Hj signals, all evidence of the isomeric nature of the product (Figure 5.36). The 6-Hj signals are both composed of 8 lines as required by the ABX system (CH2CH), while the 5-H resonances appear as triplets. 

Some idea of the difficulties in determining the structure of the penicillins is illustrated by the conversion of benzylpenicillin in acid solution, first to benzyl-penillic acid and then to benzylpenilloic acid. 

H22N20i,S, D-a-Benzylpenilloic acid monohydrate, 44B, 462 5H22N2O7, N-Acetylactinobolin, 42B, 384 5H23NO4, Cycloheximide, 43B, 642... 

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