Efficient syntheses of (-)-arbusclin D and (+)-4-epi-arbusclin D are reported. By these syntheses the C-4 stereochemistry of arbusclin D and the absolute configuration of (-)-arbusclin D have been determined to be a s shown in structure 1. The biological activities, such as cytotoxic activity toward P-388 lymphocytic leukemia, plant growth regulating activity, and antimicrobial activity of compounds 1, 3, 7, 9, 12, and 14 were also studied.