Ohashi Atsushi
Division of Supramolecular Science, Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), Ikoma City, Nara 630-0101, Japan.
Chirality. 2002 Jul;14(7):573-7. doi: 10.1002/chir.10082.
Using a series of the rhodium complexes with (1S,2S)-1-(R(1))methylphosphino-2-(R(2))(R(3))phosphinoethane (R(1), R(2) and R(3) = 1-adamantyl, t-butyl, cyclohexyl, cyclopentyl, methyl; abbreviated as unsymmetrical BisP*), very high enantioselectivities were observed when the di- or tri- substituted and tetra-substituted dehydro-alpha-amino acid derivatives were used as the substrates. The main factor to give high enantioselectivity is the repulsive interaction between the functional groups of the substrate and the bulky substituents of the unsymmetrical BisP*. Since the unsymmetrical BisP* has two independent chiral phosphorous atoms in the vicinity of the active site, the higher enantioselectivity than those by the C2 symmetric BisP* complexes can be obtained. Moreover, the fine-tuning to obtain extremely high enantioselectivity may be possible by changing the combination of the substituents on the two phosphorous atoms of the unsymmetrical BisP*.
使用一系列含有(1S,2S)-1-(R(1))甲基膦基-2-(R(2))(R(3))膦基乙烷（R(1)、R(2)和R(3) = 1-金刚烷基、叔丁基、环己基、环戊基、甲基；简称为不对称双膦配体BisP*）的铑配合物，当使用二取代或三取代以及四取代的脱氢-α-氨基酸衍生物作为底物时，观察到了非常高的对映选择性。产生高对映选择性的主要因素是底物的官能团与不对称双膦配体BisP的庞大取代基之间的排斥相互作用。由于不对称双膦配体BisP在活性位点附近有两个独立的手性磷原子，因此可以获得比C2对称双膦配体配合物更高的对映选择性。此外，通过改变不对称双膦配体BisP*两个磷原子上取代基的组合，有可能实现对极高对映选择性的精细调节。
