5 ALB [AlLibis(binaphthoxide)]錯体を用いた生物活性物質の実践的触媒的不斉合成(口頭発表の部)

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Heterobimetallic complexes function as both a Brφnsted base and a Lewis acid, making possible a variety of new asymmetric catalyses. Among them, ALB [AlLibis(binaphthoxide)] complex is an effective catalyst for asymmetric Michael reactions, tandem Michael-aldol reactions, and hydrophosphonylations of aldehydes. Herein we describe the applications of these reactions to practical catalytic asymmetric syntheses of several bioactive compounds. 1) Practical catalytic asymmetric synthesis of strychnos alkaloids The key Michael reaction promoted efficiently by ALB (0.3mol%) and KO/Bu (0.27mol%) in the presence of activated MS4A gave 2 in 98% yield and 99%ee. The Michael adduct 2 was converted to the tricyclic compound 9 using a Fisher indol synthesis and an amide coupling as key steps. Finally a first catalytic asymmetric total synthesis of 20-deethyl tubifolidine has been achieved through a key cyclization of 9 using DDQ. We hope to reveal our catalytic asymmetric total synthesis of (-)-tubifolidine, being currently under investigation, at the meeting. 2) Practical catalytic asymmetric synthesis of a prostaglandin derivative The three-component coupling product 10 was synthesized using a key tandem Michael-aldol reaction promoted efficiently by ALB (10mol%) in 86% yield and 91%ee, before the conversion to the enone 11. After recrystallization, optically pure 11 was transformed to the enone 14 through a hydrosilylation, a stereoselective reduction, and an aldol condensation via titanium-enolate, as key steps. Finally 11-deoxy-PGF_<1α> has been efficiently synthesized through a key asymmetric epoxidation of 14 using TBHP catalyzed by La-BINOL complex.
天然有機化合物討論会の論文
1997-07-20

5 ALB [AlLibis(binaphthoxide)]錯体を用いた生物活性物質の実践的触媒的不斉合成(口頭発表の部)

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