Asymmetric reduction of cyclic imines with chiral sodium acyloxyborohydrides
Asymmetric reduction of cyclic imines with chiral sodium acyloxyborohydrides
复制标题
手性酰氧基硼氢化钠对环状亚胺的不对称还原
DOI：
10.1039/p19830000265
复制
发表时间：
1983
期刊：
影响因子：
--
通讯作者：
T. Iwakuma
中科院分区：
文献类型：
--
作者：
Koichiro Yamada;M. Takeda;T. Iwakuma
研究了手性酰氧基硼氢化钠（5a-i）对前手性环亚胺的不对称还原反应。在这些新的还原剂中，三酰氧基硼氢化钠（5c-f），衍生自NaBH 4（1当量）。和（S）-N-酰基脯氨酸（3当量），在四氢呋喃中还原3，4-二氢罂粟碱（2）得到（S）-去甲劳丹核苷（3）盐酸盐，光学产率为60%。N-苄氧基羰基衍生物（5c）可以作为粉末分离并表征。溶剂对这种不对称还原的影响已经通过使用分离的试剂（5c）进行了检查;卤代烷烃溶剂如CH 2Cl 2或CHCl 2CH 3给出了更好的化合物（3）的光学产率（70% e.e.）。试剂（5c）还以优异的光学产率（70- 86% e.e.）将其它环亚胺（6a-c）和（8）还原成相应的生物碱（7a-c）和（9），为这些生物碱的不对称合成提供了一条有效途径。还提出了这种还原的可能反应途径。
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 60% 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)(70% 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 (70–86% e.e.), providing an effective route to the asymmetric synthesis of these alkaloids. A possible reaction path for this reduction is also presented.