Proline-catalyzed asymmetric addition reaction of 9-tosyl-3,4-dihydro-beta-carboline with ketones.
[reaction: see text] 9-Tosyl-3,4-dihydro-beta-carboline (1) reacted with a ketone in the presence of (S)-proline as a catalyst to give the corresponding addition product in good yield and high enantioselectivity. In the process, a small amount of water was found to affect the stereoselectivity of the products. The system was applied to reaction of compound 1 and 3-buten-2-one to give 3,4,6,7,12,12b-hexahydro-1H-indolo[2,3-a]quinolizin-2-one, which is a versatile precursor for the synthesis of some indole alkaloids.
Itoh
Takashi
T
School of Pharmaceutical Sciences, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
Yokoya
Masashi
M
Miyauchi
Keiko
K
Nagata
Kazuhiro
K
Ohsawa
Akio
A