Synthesis of (+)- and (−)-Phaseolinic Acid by Combination of Enzymatic Hydrolysis and Chemical Transformations with Revision of the Absolute Configuration of the Natural Product

(-)-Phaseolinic acid is a metabolite of a fungus, Macrophomina phaseolina, and (-)-methylenolactocin is an antitumoral antibiotic from Penicillum sp. In the course of our studies aimed at the synthesis of enantiomerically pure g-butyrolactones4 we focused our attention on the synthesis of both enantiomers of phaseolinic acid and on the determination of their absolute configuration by means of chemical and spectroscopic correlations. The strategy was to correlate (-)-phaseolinic acid with (-)-methylenolactocin