Two Classes of Enzymes of Opposite Stereochemistry in an Organism: One for Fluorinated and Another for Nonfluorinated Substrates
作者:Tomoko Matsuda、Tadao Harada、Nobuyoshi Nakajima、Toshiyuki Itoh、Kaoru Nakamura
DOI:10.1021/jo991283k
日期:2000.1.1
observed in the reduction of hindered ketones such as isopropyl ketone, while the stereoselectivity was inverted in the reduction of ketones with electron-withdrawing atoms such as chlorine. The mechanism for the inversion in stereochemistry was investigated by enzymatic studies. Several enzymes with different stereoselectivities were isolated; one of them catalyzed the reduction of methyl ketones, and another
用白色假单胞菌干燥细胞还原甲基酮可得到对映体过量(ee)极好的(S)-醇,而三氟甲基酮的还原也可得到ee极佳的相反构型的相应醇。用三氟甲基取代甲基部分改变了体积和电子性质,检查了其对立体选择性的影响。在受阻酮(如异丙基酮)的还原中未观察到立体化学的反转,而在具有吸电子原子(如氯)的酮的还原中,立体选择性被反转。通过酶学研究了立体化学转化的机理。分离出了几种具有不同立体选择性的酶。它们之一催化甲基酮的还原,而另一种具有相反的立体选择性催化三氟甲基酮的还原。此外,将APG4和分离的酶均应用于制备规模的氟化酮还原反应,从而合成了具有优异ee的手性氟化醇。