REGIOSELECTIVE AND STEREOSELECTIVE CYCLIZATIONS - APPLICATION TO NATURAL-PRODUCTS SYNTHESIS

Cyclization of unsaturated ketyl radical anions, photochemically induced by electron transfer from triethylamine (NEt3) to unsaturated ketones, produced cyclopentanols or cyclohexanols. The cyclization reaction was regio-, stereo- and chemo- selective and gave high yields in cyclopentanols or cyclohexanols. Ketyl radical anions could also induce the ring opening of strained ring such as cyclopropanes, epoxides and 7-oxabicyclo[2.2.1]heptanes. Furthermore 3-azabicyclo[4.3.0]nonane skeletons were obtained by photoreductive cyclization of epsilon,omega-unsaturated beta-ketoamides, and azaspiranic skeletons by treatment of unsaturated beta-ketoamides or enaminoamides by Mn(OAc)3. Application of these methodologies to natural products synthesis is described.