DEVELOPMENT OF CATALYTIC ASYMMETRIC REACTIONS USING LANTANOIDS

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1) Asymmetric Diels-Alder reactions of cyclopentadiene and several dienophiles catalyzed by a chiral ytterbium complex prepared by a noble axially asymmetric chiral ligand, BINAMIDE and Yb(OTf)_3 were investigated.The reaction with bromoacryloyl amide afforded cyclo-adduct in 97% yield with 98% de and with 93% ee. The adduct was converted cyclosarkomycin, a key intermediate for the synthesis of antitumor antibiotics sarkomycin (overall 6%, 10 steps). Although a diastereoselective synthesis of optically active cyclosarkomycin has been reported, this is the first catalytic enentioselective synthesis cyclosarkomycin.The reaction with a fumaric acid derivative gave a mixture of adduct in 83% yield with 52% de and with 84% ee. The adduct was converted to a key intermediate for the synthesis of TXA2 antagonist, ONO-8809 which was developed by Ono company. This fumaric acid derivative also reacted with siloxydiene to give a cyclohexene derivative with low enantioselectivity (13% ee).2) A new allylic halogenation and Pictet-Spengler reaction of imines, both catalyzed by Yb(OTf)_3 were developed. Asymmetric version of these reactions will be developed in future.