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■ Nucleophilic Asymmetric Epoxidation Catalyzed by Cyclic Guanidines

Tetsuya Kita, Bongki Shin, Yuichi Hashimoto, and Kazuo Nagasawa*

*Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan

Abstract

Asymmetric nucleophilic epoxidation of chalcone and its derivatives was studied using chiral cyclic guanidine compounds. Pentacyclic guanidine 1a, which has a characteristic closed-type cavity, catalyzed the reaction to give epoxides with 39-60% ee. The newly developed tricyclic guanidine 4 drastically accelerated the reaction, and induced the asymmetric induction of chalcones with almost the same level of 1a.