Abstract
Ring formation and syntheses of natural products were carried out utilizing latent powers of polyfunctional groups. Thus two novel methodologies, an intramolecular double Michael reaction and a tandem intramolecular Michael-aldol reaction, have been developed. Atisirene (7), atisine (18), pentalenic acid (28), pentalenene (29), epilupinine (32), and tylophorine (36) were synthesized using the intramolecular double Michael reaction. Several frameworks of natural products, possessing polycyclic systems fused to cyclobutane, were constructed by the tandem intramolecular Michaelaldol reaction. Furthermore, various natural products, testosterone (67), androsterone (68), 3-oxosilphinene (72), Δ9(12)-capnellene (78), as well as 1β-methylcarbapenem antibiotic (96) were stereoselectively synthesized by means of the intramolecular Diels-Alder reaction or the intramolecular 1, 3-dipolar cycloaddition.
