New coumarins from Harbouria trachypleura: isolation and synthesis

Two known furanocoumarins, (+)-oxypeucedanin and (+)-saxalin, two known coumarins, umbelliferone and (+)-epoxysuberosin, and two new coumarins (+)-trachypleuranin-A and (±)-trachypleuranin-B, were isolated from the methanol extract of Harbouria trachypleura. An efficient five-step asymmetric synthesis of (+)-trachypleuranin-A was performed using a sequential [3,3] Claisen–Cope rearrangement and a Shi asymmetric epoxidation. (±)-Trachypleuranin-B, a chlorinated coumarin, was synthesized from (±)-epoxysuberosin.