Table 3.
Synthesis of d‐ and l‐2 a–j from 1 a–j.[a]
| PAL(H359Y)/LAAD cascade | PAL(WT)/DAAO cascade | PAL(WT) only | |||||
|---|---|---|---|---|---|---|---|
| Subs. | R | Conv. [%][b] | ee d‐2 [%][b] | Conv. [%][b] | ee l‐2 [%][b] | Conv. [%][b] | ee l‐2 [%][b] |
| 1 a | p‐NO2 | 79 | >99 | 82 | >99 | 84 | rac |
| 1 b | m‐NO2 | 74 | 98 | 76 | >99 | 79 | 89 |
| 1 c | o‐NO2 | 80 | 98 | 83 | >99 | 91 | rac |
| 1 d | p‐CF3 | 64 | 98 | 66 | >99 | 65 | 76 |
| 1 e | p‐CN | 77 | 99 | 79 | >99 | 72 | 70 |
| 1 f | o‐F | 77 | >99 | n.r. | n.r. | 84 | >99 |
| 1 g | m‐F | 74 | 98 | n.r. | n.r. | 67 | >99 |
| 1 h | p‐F | 62 | >99 | n.r. | n.r. | 53 | >99 |
| 1 i | 3,5‐F2 | 78 | >99 | n.r. | n.r. | 57 | 97 |
| 1 j | m‐Cl | 63 | 99 | n.r. | n.r. | 86 | >99 |
[a] Reaction conditions: 5 mm subs., 5 m NH4OH, 25 mg mL−1 PAL E. coli wet cells, 35 mg mL−1 LAAD or DAAO E. coli wet cells, 40 equiv NH3:BH3, pH 9.6, 37 °C, 220 rpm. [b] Determined by HPLC analysis (yields of isolated products are given in the Supporting Information). n.r.=not required, because of the high ee value products from the PAL‐mediated reaction alone.