Regio- and Stereoselective Reduction of Substituted 1.3-Dicarbonyl Compounds by Use of Bakers' Yeast

1. 添加剂对面包酵母还原1-氯-2,4-烷二酮的影响——在反应水溶液中加入2 mol/L的SrCl_2可提高还原产物的% ee值。其他金属氯化物也表现出类似的效果，尽管没有那么大。这种作用可归因于添加剂对多重还原酶的选择性激活或抑制。烘焙酵母还原1-乙酰氧基-2,4-烷二酮——与还原1-乙酰氧基-2-羟基-4-烷二酮的95 - 99% ee相比，还原在40 - 90% ee下产生(S)-1-乙酰氧基-2-羟基-4-烷二酮。% ee值略有下降可归因于C-4上的氧官能团的存在。氧基有效地抑制了乙酰氧基的水解，这种水解发生在1-乙酰氧基-2-烷酮中，并产生了1,2-二醇作为副产物。具有旋光活性的三功能产物是有用的手性合成物。利用面包师酵母无细胞萃取物进行高效不对称还原——发现无细胞萃取物使用催化量的NADPH，以葡萄糖为氢化物来源，不添加任何辅助因子再生酶，以59 - 88%的产率和95 - 99%的产率将1-乙酰氧基-2-烷醇还原为1-乙酰氧基-2-烷醇。该方法有望适用于1-氯和1-乙酰氧基-2,4-烷二酮。

1. Effects of Additives of the Bakers' Yeast Reduction of 1-Chloro-2,4-alkanediones---The % ee values of reduction products were found to be enhanced by addition of SrCl_2 in 2 mol/L to the aqueous reaction solution. Other metal chlorides also exhibited similar effects, though not so large. The effects can be attributed to selective activation or inhibition of additives toward plural reducing enzymes.2. Bakers' Yeast Reduction of 1-Acetoxy-2,4-alkanediones ---The reduction produced (S)-1-acetoxy-2-hydroxy-4-alkanones in 40 - 90% ee, as compared with the reduction of 1-acetoxy-2-alkanones with 95 - >99% ee. The somewhat diminished % ee values can be attributed to the presence of an oxo functional group at C-4. The oxo group effectively suppressed the hydrolysis of the acetoxy group, which occurred for 1-acetoxy-2-alkanones and produces 1,2-diols as by-product. The optically active trifunctional products are useful as chiral synthons.3. Highly Efficient Asymmetric Reduction by Use of Bakers' Yeast Cell-Free Extract---The cell-free extract was found to reduce 1-acetoxy-2-alkanones to 1-acetoxy-2-alkanols in 59 - 88% yield and 95 - >99% ee by use of a catalytic amount of NADPH with glucose as hydride source and without addition of any enzyme for the cofactor regeneration. This method is expected to be applicable to 1-chloro- and 1-acetoxy-2,4-alkanediones.