A New Synthesis of 3-Methyl-3-cyclopentene-1-carboxylic Acid and Derivatives

Abstract

Recently we reported the synthesis of desether-muscarine,¹ a compound of interesting cholinergic activity. The starting material for this synthesis was the 3-methyl-3-cyclopentene-l-carboxylic acid (II) already synthesized through photochemical addition of ethyl diazoacetate to isoprene and subsequent pyrolisis of I ² Following this synthetic route it was difficult to obtain such compound and mostly starting material was recovered together with a little photoaddition product. In order to have enough compound for the synthesis of desethermuscarine with the aim to separate its optical isomers, a new synthesis of I, from isoprene and ethyl diazoacetate via copper-catalized addition,³ has been sought and is reported here.