Total Synthesis of (-)-Ribesin B and its Structural Revision

A highly symmetric dihydrofuran lignan, ribesin B (1), isolated from the leaves of Ribes nigrum, was synthesized via a process whereby the key step was a sequential Michael addition–carbocyclization. However, the NMR spectral features of the synthesized 1 were inconsistent with those of the natural product 1. Thus, the chemical synthesis of the isovanillin-moiety containing compound 2 from chiral propargyl alcohol was conducted through a process that included lipase-catalyzed kinetic resolution. The NMR spectrum of 2 was perfectly superimposable to that of naturally isolated ribesin B. Consequently, the structure of ribesin B was revised to be that of 2.