Table 1.
Deracemization of benzylisoquinolines rac-1 to berbines (S)-2 by a stepwise transformation using MAO in the first step and BBE in the second.
| Substrate | Procedure[a] | Time[b] [h] | (S)-2[c] [%] | ee (2)[d] [%] |
|---|---|---|---|---|
| 1 a | A | 48+24 | 93 | >97 |
| 1 a | B | 48+24 | 90 | >97 |
| 1 b | A | 48+24 | 97 | >97 |
| 1 b | B | 48+24 | 95 | >97 |
| 1 c | A | 72+24 | 79[e] | >97 |
| 1 c | B | 72+24 | 79[e] | >97 |
[a]
Procedure A: direct addition of BBE to the reaction mixture after completion of the first step. Procedure B: addition of BBE after removal of MAO by centrifugation.
[b]
Reaction time for 1st+2nd step.
[c]
Determined by HPLC on an achiral stationary phase.
[d]
Determined by HPLC on a chiral stationary phase.
[e]
4 % of regioisomer formed.