P-Methoxybenzyl esters

The piperonyl ester can be prepared from an amino acid ester and the benzyl alcohol (imidazole/dioxane, 25°, 12 h, 85% yield) or from an amino acid and the benzyl chloride (Et3N, DMF, 25°, 57-95% yield). It is cleaved, more readily than a p-methoxybenzyl ester, by acidic hydrolysis (CF3COOH, 25°, 5 min, 91% yield). ... 

The preparation of 6-y5-iodopenicillanic acid (25) from 6-APA (8) was reported by Pfizer chemists Scheme 6.7) [64]. The p-methoxybenzyl ester of 6-a-hydroxypenicillanic acid (43), prepared by the method of Sheehan et al. [65], was converted to the trifiate (44), which upon reaction with sodium iodide gave the 6-yS-iodopenicillanate ester (45) deprotection then provided the free acid (25). 

The addition of aqueous hydrochloric acid to the azabicyclohexanes 143a,b causes breakdown of the aziridine ring. In contrast to tliis, the p-methoxybenzyl ester 146 can be hydrolyzed to the unstable carboxylic... 

Carboxyl protection. Tetralyl esters can be selectively cleaved by Me SiCl-Nal in MeCN at room temperature without affecting benzhydryl esters and p-methoxybenzyl esters. 

Synonyms p-Anisyl phenylacetate Anisyl a-toluate p-M ethoxy benzyl phenyl acetate Phenylacetic acid, p-methoxybenzyl ester... 

Deprotection of Derivatives of Carboxylic Acids.—Methyl esters are demethylated with anhydrous trifluoroacetic acid, in yields ranging from quantitative to 2%. Triarylamine radical cations react with benzyl esters in an oxidative cleavage reaction to give carboxylic acids yields are best with p-methoxybenzyl esters. ... 

The action of methyl iodide and strong anhydrous base on 6j8-tritylaraino-penicillinates effects. S-alkylation and 1,2- bond rupture, to form the 1,2-seco-penicillins (114). With p-methoxybenzyl esters, dialkylation may occur, giving (115 t) as a product. ... 

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