PALLADIUM-MEDIATED ASYMMETRIC-SYNTHESIS OF CIS-3,6-DISUBSTITUTED CYCLOHEXENES - A SHORT TOTAL SYNTHESIS OF OPTICALLY-ACTIVE (+)-GAMMA-LYCORANE

An asymmetric alkylation of the cyclohexenediol derivative 6 with 2c or 2d using a catalytic amount of Pd(OAc)(2) in the presence of(S)-BINAPO was achieved. The alkylation products 15 (49% ee, 53% yield) and 25 (40% ee, 63% yield) were further treated with a palladium catalyst to give the oxindole derivatives 14 and 26. The absolute configuration of the monoalkylated product 15 was determined by the CD exiton method. From 6, a total synthesis of (+)-gamma-lycorane (9) was accomplished in five steps in 23% overall yield and 46% ee.