Treatment of 3-(2-ethynylphenyl)prop-2-ynyl benzenesulfinate with 2.5-mol % of [RhCl(CO)(2)](2) at 40 degrees C under an atmosphere of CO effected the successive 2,3-sigmatropic rearrangement and carbonylative [2 + 2 + 1] ring-closing reaction to afford the 8-(phenylsulfonyl)-1H-cyclopent[a]-inden-2-one in a high yield. Chemical modification of the ring-closed product via lipase-mediated optical resolution produced tile optically active 3-acetoxy-3a-cyclohexyloxy-3,3a-dihydrocyclopent[a]indene skeleton, the core carbon framework of cyanosporasides A and B.