Hydrogenation with Chiral, Nonracemic Catalysts

Catalytic Hydrogenation with Chiral, Nonracemic Catalysts 

In several syntheses scattered throughout this book, an alkenyl amino acid was prepared. In all of those cases, reduction of the double bond leads to the saturated amino acid. If the double bond contains a substituent, the amino group or another. S 

When the amino group is attached to the alkene as in 5.246, hydrogenation of the double bond can generate a chiral center if a chiral catalyst is used for hydrogenation. In this example, a chiral catalyst developed by Achiwa (5.247) allowed reduction of methyl 3-(N-acetylamino)but-2Z-enoate (5.24) to give methyl 3-(N-acetylamino)butanoate (5,248), quantitatively (53%ee, R).l 3 Similarly, methyl 3-0 -acetylamino)-3-phenyl-propanoate was prepared in 90% yield (47%ee, R). 

Noyori used the BINAP-Ru(II) catalyst [5.250, where BINAP is 2,2 -bis-(diphenylphosphino)-l,l -binaphthyl] to reduce p-aminopropenoic acid as well as several derivatives. Reduction of 5.246 with R-BINAP (5,250) gave a good yield of 5,248, but with only 5%ee, R. In several examples, the -isomer showed greater 

12 Ohshiro, S. Kuroda, K. Fujita. T. Yakugaku Zasshi, 1967, 87,1184 Chertu Abstr., 1968. 68 40031w]. 

---