Carbamate analogues of (−)‐physostigmine: In vitro inhibition of acetyl‐ and butyrylcholinesterase

Reaction of (−)‐eseroline (1) with alkyl, aryl and aralkylisocyanates afforded a series of carbamate analogues of (−)‐physostigmine (2) which were assayed for inhibition of acetyl‐ and butyrylcholinesterase (AChE and BChE, respectively) in vitro. Included in this study were two N‐alkyl‐substituted carbamates 9 and 14 obtained from (−)‐eseroline (1) with dialkylcarbamoyl chlorides, and allophanates 12 and 13 obtained as by‐products in the reaction of 1 and benzylcarbamoyl eseroline (8) with benzyl isocyanate. Whereas none of the analogues studied was more potent than 2 against electric eel AChE, and carbamates 6, 7 and 8 were all more than 3 times more potent against human plasma BChE than 2.