6429-04-5Relevant articles and documents
Total synthesis of 8-epi-javaberine A and javaberine A
Yamamoto, Yasutomo,Tabuchi, Yuri,Baba, Ayana,Hideshima, Kumiko,Nakano, Mai,Miyawaki, Akari,Tomioka, Kiyoshi
, p. 1311 - 1321 (2016/11/07)
The total synthesis of berberine alkaloid javaberine A was examined. The B/C ring of berberine was successfully constructed by sequential Bischler-Napieralski cyclization-reduction protocols, and final demethylation afforded both javaberine A and its epimer.
Asymmetric Reduction of Cyclic Imines with Chiral Sodium Acyloxyborohydrides
Yamada, Koichiro,Takeda, Mikio,Iwakuma, Takeo
, p. 265 - 270 (2007/10/02)
Asymmetric reduction of prochiral cyclic imines with chiral sodium acyloxyborohydrides (5a-i), which are easily prepared by the reaction of NaBH4 with various N-acyl α-amino-acids, has been investigated.Of these new reducing agents, triacyloxyborohydrides (5c-f), derived from NaBH4 (1 equiv.) and (S)-N-acylproline (3 equiv.), were found to reduce 3,4-dihydropapaverine (2) in tetrahydrofuran to (S)-norlaudanosine (3) hydrochloride in 60percent optical yield.The N-benzyloxycarbonyl derivative (5c) could be isolated as a powder and characterized.The effect of solvents on this asymmetric reduction has been examined by the use of the isolated reagent (5c); halogenated alkane solvents such as CH2Cl2 or CHCl2CH3 gave a better optical yield of compound (3) (79percent e.e.).The reagent (5c) also reduced other cyclic imines (6a-c) and (8) to the corresponding alkaloids (7a-c) and (9) in excellent optical yields (70-86percent e.e.), providing an effective route to the asymmetric synthesis of these alkaloids.A possible reaction path for this reduction is also presented.