The cleavage reaction of cyclopropane ring is one of the useful method in organic synthesis. Especially the sequence of cyclopropanation-homoconjugate addition is one of the accessible methods for the synthesis of natural products possessing ring- and side-chain contiguous chiral centers. This report deals with the synthetic studies of biologically active natural products possessing such chiral centers by using the ring opening reaction of double activated cyclopropanes. Cyclopropane derivatives (3-8) have been synthesized from methyl acetoacetate by alkylation, diazo transfer followed by copper-mediated cyclopropanation. The stereochemical course of homoconjugate addition to an activated cyclopropane has been elucidated. The opening reactions proceed with inversion of absolute configuration at the apical carbon of the cyclopropane. The various adducts (16,22,25,31,44 and 46) were obtained by homoconjugate addition of nucleophiles (Gilmann reagent, Grignard reagents, cyanide anion, methanol etc.) to cyclopropane derivatives. The adducts were converted effectively into the synthetic intermediate of steroids (21 and 27), iridoid monoterpenes (30,36,37 and 38), the synthetic intermediate of thienamycin (42) and epiinvictolide (53) by routine functional group transformation.
