d-proline and N-boc-5-hydroxy-l-proline are key chiral intermediates in the production of eletriptan and saxagliptin, respectively. An efficient proline racemase–proline dehydrogenase cascade was developed for the enantioselective production of d-proline. It included the racemization of l-proline to dl-proline and the enantioselective dehydrogenation of l-proline in DL-proline. The racemization of l-proline to dl-proline used an engineered proline racemase (ProR). l-proline up to 1000 g/L could be racemized to dl-proline with 1 g/L of wet Escherichia coli cells expressing ProR within 48 h. The efficient dehydrogenation of l-proline in dl-proline was achieved using whole cells of proline dehydrogenase-producing Pseudomonas pseudoalcaligenes XW-40. Moreover, using a cell-recycling strategy, d-proline was obtained in 45.7% yield with an enantiomeric excess of 99.6%. N-boc-5-hydroxy-l-proline was also synthesized from l-glutamate semialdehyde, a dehydrogenated product of l-proline, in a 16.7% yield. The developed proline racemase–proline dehydrogenase cascade exhibits great potential and economic competitiveness for manufacturing d-proline and N-boc-5-hydroxy-l-proline from l-proline.

d-脯氨酸和N -boc-5-羟基-l-脯氨酸分别是生产依曲坦和沙格列汀的关键手性中间体。开发了一种高效的脯氨酸消旋酶-脯氨酸脱氢酶级联反应，用于对映选择性生产d-脯氨酸。它包括l-脯氨酸消旋为dl-脯氨酸和l-脯氨酸在DL-脯氨酸中的对映选择性脱氢。l-脯氨酸到dl-脯氨酸的消旋化使用工程化脯氨酸消旋酶(ProR)。l-脯氨酸高达 1000 g/L 可与 1 g/L 湿大肠杆菌外消旋成dl-脯氨酸在 48 小时内表达 ProR 的细胞。使用产生脯氨酸脱氢酶的Pseudomonas pseudoalcaligenes XW-40的全细胞实现了dl-脯氨酸中l-脯氨酸的有效脱氢。此外，使用细胞回收策略，以 45.7% 的产率获得了d-脯氨酸，对映体过量为 99.6%。N - boc -5-羟基-L-脯氨酸也由L-谷氨酸半醛（L-脯氨酸的脱氢产物）合成，产率为16.7%。开发的脯氨酸消旋酶-脯氨酸脱氢酶级联在制造d-脯氨酸和N方面表现出巨大的潜力和经济竞争力-boc-5-羟基- l-脯氨酸来自l-脯氨酸。