Phramacological properties of esters of 1-alkyl-2-hydroxyalkylpyrrolidine and their quaternary derivatives.

A series of esters of 1-alkyl-2-hydroxyalkylpyrrolidine and their quaternary derivatives have been shown to possess significant anti-acetylcholine activity. The benzilic acid esters were the most active, followed by xanthene-9-carboxylic acid, fluorene-9-carboxylic acid and diphenylacetic acid esters in that order. The quaternary derivatives were more active than their corresponding tertiary compounds both in vivo and in vitro. The most active compound of the series tested in vivo was (1-methylpyrrolid-2-yl)methyl benzilate methiodide and was as potent as atropine. There was a progressive decrease in anti-acetylcholine activity and a proportional increase in local anaesthetic activity as the number of carbon atoms was increased from 1 to 3 in the pyrrolidyl side-chain of the tertiary salts of the benzilic acid ester series. Likewise increasing the size of the group on the nitrogen atom led to a decrease in anti-acetylcholine activity and an increase in local anaesthetic activity. Quaternization of the tertiary salts resulted in a loss of local anaesthetic activity. Most of the compounds tested possessed some antihistamine properties, while papaverine-like activity was confined to the tertiary salts only. No significant neuromuscular blocking activity was evident.