Development of Several New Reactions and Their Application to the Total Synthesis of Biologically Active Natural Products ：Synthesis of Linderol A and Determination of Its Absolute Configuration

Linderol A （1）, a monoterpene-polyketide, was isolated in 1995 from the fresh bark of Lindera umbellata （Lauraceae）, and its absolute structure was not determined. It was also reported potent inhibitory activity of 1 on the melanin biosynthesis of the cultured B-16 melanoma cells. See Fig. 1. On the other hand, we reported in 1995 an interesting multi-tandem reaction of coumarin derivatives （2; W = electron withdrawing group） by treatment with CH2 = S（O）Me2 to yield stereoselectively a tricyclic 2-substituted （4） via a cyclopropane intermediate （3） cyclopenta [ b ] benzofuran-3-ol derivative （Scheme 1）.