The Synthesis and Configuration of Fukiic Acid Derivatives

Abstract

Abstract The methylation of 3,4-dimethoxyphenylpyruvic acid (II) gave the corresponding methyl ester (III), which was then subjected to a Wittig reaction with carbomethoxymethylenetriphenylphosphorane to give the corresponding fumaric (IVa) and maleic (IVb) acid derivatives in a 1:3 ratio. The cis-hydroxylation of IVa and IVb with an aqueous solution of potassium permanganate and magnesium sulfate gave methyl (±)-thero-2,3-dihydroxy-4-(3,4-dimethoxyphenyl)-3-methoxycarbonylbutyrate (Va) and its (±)-erythro-isomer (Vb) respectively. The dimethyl esters, (±)-Va and (±)-Vb, were converted to the corresponding monomethyl esters, (±)-VIIa and (±)-VIIb respectively, via two dicarboxylic acid derivatives, (±)-VIa and (±)-VIb. The resolution of (±)-VIIb with brucine gave (+)-VIIb and (−)-VIIb, which were then converted to (+)-Vb and (+)-VIb and to (−)-Vb and (−)-VIb respectively. The synthetic (+)-Vb was shown to be identical with the natural O,O′-dimethylfukiic acid dimethyl ester by a mixed fusion and by comparisons of their IR and NMR spectra. From the present study it is evident that natural fukiic acid has an erythro configuration.