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Paper | Special issue | Vol 76, No. 2, 2008, pp.1191-1204
Published online, 2nd June, 2008
DOI: 10.3987/COM-08-S(N)81
A New Chiral Synthesis of a Bicyclic Enedione Containing a Seven-Membered Ring Mediated by a Combination of Chiral Amine and Brønsted Acid

Takashi Nagamine, Kohei Inomata,* and Yasuyuki Endo*

*Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai 981-8558, Japan

Abstract

Several chiral amines bearing a heterocyclic moiety such as pyrrolidine, piperazine or tetrazole were prepared from L-phenylalanine. The enantioselectivity of the intramolecular asymmetric aldol reaction mediated by a combination of the synthetic chiral amine and a Brønsted acid to construct an enedione containing a seven-membered ring was examined in detail. A remarkable increase of enantioselectivity depending on the amount of Brønsted acid was observed.