Pteridicacid A (1) is a spirocyclic octaketide produced by the phytoepiphytic actinomycete Streptomyces hygroscopicus TP-A0451 and possesses potent plant-growth-promoting activity comparable to that of indole-3-acetic acid. The enantioselective totalsynthesis of this natural product was achieved by employing the Sn(OTf)(2)-mediated Evans aldol reaction and the Fukuyama acetylenic coupling reaction