Convenient, scalable synthesis of 2-methyl-3-(3′,3′-carboxymethylpropyl)-1,4-naphthoquinone, the principal vitamin K urinary metabolite

The ultimate metabolite of vitamin K, 2-methyl-3-(3′,3′-carboxymethylpropyl)-1,4-naphthoquinone (1), has been shown to be biologically active and may be used as a measure of vitamin K levels in the body. We report a facile, five-step synthesis of 1 that requires only two isolated intermediates and a single chromatographic purification, and provides the title product in 26% overall yield. The structure of one of the intermediates was confirmed by X-ray crystallography.