Total synthesis of swazinecic acid dilactone. Part 1. Synthesis of 2-hydroxy-2-methyl-3,5-dimethylenehexanedioic acid as an intermediate

Abstract

2- Hydroxy-2-methyl-3,5-dimethylenehexanedioic acid (8) was synthesised in two ways : (a) by condensation of diethyl malonate with ethyl 3-bromomethyl-2-ethoxycarbonyloxy-2-methylbut-3-enoate followed by hydrolysis and a Mannich reaction with dimethylamine–formaldehyde, and (b) by an organocopper coupling reaction with ethyl 3-bromomethyl-2-methyl-2-trimethylsilyloxybut-3-enoate and lithium α-ethoxycarbonylvinyl(hex-1-ynyl)-cuprate followed by hydrolysis.