DIASTEREOSELECTIVE IODOCARBOCYCLIZATION REACTION OF 2-OXY-4-PENTENYLMALONATE OR 3-OXY-4-PENTENYLMALONATE DERIVATIVES

1,2- Or 1,3-asymmetric induction in the iodocarbocyclization reaction of 4-pentenylmalonate derivatives having a stereogenic center at an al lylic or a homoallylic position has been investigated. ,The iodocarboc yclization reactions of 3-oxy-4-pentenylmalonate derivatives proceeded with high cis-selectivity through stereoelectronic control of the oxy genated substituent at an allylic position. In the reaction of (S)-2-s iloxy-4-pentenylmalonate, an excellent diastereoselectivity was achiev ed through the utilization of double stereodifferentiation with a chir al titanium catalyst. Furthermore, as an application of the present re action, the asymmetric syntheses of cyclosarkomycin and a synthetic in termediate of brefeldin A from optically pure 2- and 3-oxy-4-pentenylm alonate derivatives are also described.