CHIRAL RHODIUM COMPLEX-CATALYZED ASYMMETRIC CYCLIZATION AND ITS APPLICATION TO THE SYNTHESIS OF NATURAL-PRODUCTS

Rh(I)-catalyzed cyclization of substituted 4-pentenals into cyclopentanones found first by our laboratory was developed into the highly diastereoselective and enantioselective asymmetric cyclization by using the Rh(I)-complex with chiral ligand such as BINAP, and (+)-DIPMC. Cationic Rh (1) with BINAP afforded the best asymmetric cyclization in chemical yields and enantioselectivity as well as the diastereoselectivity. This cyclization method could be successfully applied for the synthesis of iridomyrmecin and isoiridomyrmecin from monene. In addition, Rh(I)-catalyzed cyclization of oct-6-enal with the cis-cyclohexane-1,2-dioxy function at C 3-position afforded two conformational diastereomers due to a cis-cyclohexane-1, 2-diol moiety. The interesting findings found by our group are summarized as main topics in this paper.