Wittig Reactions of Maleimide Derived Stabilized Ylides with Alkyl Pyruvates: Concise Approach to Methyl Ester of (±)-Chaetogline A

A facile synthesis of methyl ester of chaetogline A is reported starting from the corresponding methyl 1-methyltryptophanate derived maleimide. A stereoselective Wittig olefination with a carbonyl function in methyl pyruvate followed by phosphorous pentoxide induced regioselective dehydrative cyclization are the essential reactions. An acid induced thermodynamically driven stereoselective β- to α-position migration of the exocyclic carbon−carbon double unit in ethyl tetrahydroindolizinoindolylidenepropanoate is described.