Approaches to cytochalasan synthesis: preparation and Diels–Alder reactions of 3-alkyl- and 3-acyl-Δ3-pyrrolin-2-ones

Abstract

A series of N-protected Δ³-pyrrolin-2-ones has been prepared, and their Diels–Alder reactivity assessed. 3-Alkyl- and 3-(oximinoalkyl)-1,5-dibenzyl-Δ³-pyrrolin-2-ones were found to isomerize to their 5-benzylidenepyrrolidinone isomers rather than undergo Diels–Alder reactions. In contrast N-acyl- and N-arylsulphonyl-Δ³-pyrrolin-2-ones were found to undergo Diels–Alder reactions with the major products being formed by an endo-selective cycloaddition to the less hindered face of the dienophile.