Development of a method for the asymmetric construction of substituted citric acid structures and synthesis of natural products as leading compounds for drug discovery

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Alkylcitrate family of natural products such as viridiofungin and trachyspic acid have attracted so much attention due to their potent inhibitory activities against biologically important enzymes (e.g. serine-palmitoyl transferase, phospholipase A2, heparanase, squalene synthase) as well as synthetically intriguing structures. However, a general method for the construction of highly functionalized citric acid structures containing a quaternary center has not been developed yet. In this research, we focused on developing a general and efficient method for the asymmetric synthesis of such citric acid structures, and aimed to achieve total syntheses of alkylcitrate family of natural products.In the former research, we developed a highly efficient asymmetric Baylis-Hillman reaction using dried β-isocupreidine (β-ICD). In addition, we succeeded in synthesizing two enantio-complementary catalysts to β-ICD starting from quinine. We found that β-ICD-catalyzed Baylis-Hillman reaction of γ-(p-methoxybenzyl)oxy-α-ketobutanoate proceeded with high enantioselectivity in good yield. We also examined asymmetric Mukaiyama aldol reaction of γ-(p-methoxybenzyl)oxy-α-ketobutanoate with the ketne silyl ether drived from S-tert-butyl pent-4-enethioate using several BOX-Cu catalysts but the encouraging results were not obtained.In the latter research, we achieved the first total synthesis of (+)-trachyspic acid as well as (±)-trachyspic acid based on Nozaki-Hiyama-Kishi reaction, therby determining its absolute structure. Furthermore, we accomplished the first total synthesis of (-)-virifiofungin A employing olefin cross metathesis as a key step.