Penaldic acid

P. Gamer and J. M. Park, Glycosyl ot-amino acids via stereocontrolled buildup of a penaldic acid equivalent. An asymmetric synthesis of thymine polyoxin C, Tetrahedron Lett. 30 5065 (1989). 

Penicilloic acids (III) react instantly in aqueous solution with mercuric chloride 19d giving penicillamine (VII) and penaldic acid (VI). Penaldic acids decarboxylate rapidly to form the corresponding penilloaldehyde (VIII). This degradation forms the basis for a sensitive analytical method for benzylpenicillin. ... 

Two fragments were isolated by hydrolysis of the penicillins with acid. The first, penicillamine (3.2), was identified as p,p-dimethylcysteine by synthesis and shown to possess the unusual o-amino acid configuration. The second fragment, which retained the side-chain, was known as a penaldic acid (3.4). It behaved as a p-keto acid and lost carbon dioxide to give a penilloaldehyde... 

The penaldic acids were obtained by alkaline hydrolysis of a penicillin. Initially, this gave a dicarboxylic acid known as a penicilloic acid (3.3). Further... 

Hence, a possible explanation may be put forward that perhaps a penilloaldehyde-carboxylic acid (penaldic acid) is formed as an intermediate in the hydrolysis of penicillin, thus ... 

Fig. 23. Reaction of penicilloic acid (/) with cystine to yield penamaldic acid-cysteine mixed disulfide (//). Subsequent hydrolysis of II yields penicillamine-cysteine mixed disulfide (III) and penaldic acid (IV)...

Gamer P (1984) Stereocontrolled Addition to a Penaldic Acid Equivalent an Asymmetric Synthesis of Threo-pi-hydroxy-D-glutamic Acid. Tetrahedron Lett 25 5855... 

After neutfalization with a normal solution of sulfuric acid in the presence of phe-nolphthalein, a decinormal iodine solution is added and the reaction is allowed to evolve over 15 min. The excess iodine is titrated with a 10 mol/L thiosulfate solution. According to some authors, opening the P-lactam cycle does not stop at the stage of penicilloic acid. It leads to penaldic acid and to penicillamine in equimolar quantities. 

On the one hand, penaldic acid consumes one molecule of iodine, to give the corresponding imine. On the other hand, penicillamine consumes three molecules of iodine, to give the corresponding sulfonic acid. The direct iodometric method furnishes results that are in agreement with the microbiological ones. 

The configuration of alanilol and penaldic acid will be discussed in section V, pages 365-370. 

The formula of penicillin (IV) has three asymmetric centers one corresponds to the a-carbon atom of the amino acid penicillamine (V) the second is derived from the substituted a-formyl-a -amino acid, penaldic acid (VI), while the third asymmetric center is produced by the condensation of these two components to the thiazolidine structure present in the penicillins. The penicillamine isolated from penicillin was shown to have n configuration by conversion to n-valine. Penaldic... 

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