TOTAL SYNTHESIS OF STRYCHNINE

Strychnine is one of the most famous and complex natural products in its size. Woodward succeeded in the total synthesis of (-)-strychnine in 1954, but there were no other reports of the total synthesis of strychnine for about 40 years. In 1992, Magnus succeeded in the total synthesis of (-)-strychnine and then due to the dramatic progress of synthetic organic chemistry and organometallic chemistry, many researchers tried to synthesize ()- and (-)-strychnine by their original methods. We developed a novel synthetic method of a chiral cyclohexenyl amine derivative having an aryl group at the 2-posotion by palladium catalyst for the synthesis of (-)-mesembrine. Furthemore, (+)-crinamine, (-)-haemanthidine, and (+)-pretazettine Could be synthesized by the same procedure. Modifying this method, the total synthesis of (-)-strychnine was achieved. The chiral cyclohexenyl amine derivative having the sylyloxymethyl group at the 2-position was synthesized using the palladium catalyst. From this comopound, construction of the ABE-rings of (-)-strychnine was carried out. The C-ring was constructed using palladium-catalyzed allylic oxidation. The G-ring and then the F-ring were constructed by intramolecular Heck reaction. All cyclizations for synthesis of (+)-isostrychnine were performed using palladium catalysts. (+)-Isostrychnine was converted into (-)-strychnine by the known method. The progress of the synthesis of a chiral cyclohexenyl amine derivative having the substituent at the 2-position was described.