More detailed C,sO enriched spectra for [Me2PhPMn(CO>5] [PF6] in the entire «(CO) region may be found in ref 2. In addition, we have observed that this reaction proceeds ~4.5 times slower in D2180 as compared with H2180. The details of this isotope effect on the oxygen-exchange process will be the subject of a later publication. (28) R.

Louis, Missouri 63 166)ENZYMIC CATALYSIS in the formation of organic compounds in nature provides the most efficient and stereospecific examples of catalytic asymmetric synthesis. Readily obtainable catalysts approaching the efficiency of enzymic processes would be highly desirable and would have obvious advantages over asymmetric syntheses requiring asymmetric reagents.A few examples of non-enzymic catalytic asymmetric synthesis have been reported.1 Optically active polymers have been employed as catalysts . ,

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Catalytic asymmetric hydrogenations have been reported using soluble complexes of rhodium and chiral phosphines. 1-5 These results suggest that any prochiral olefin or other unsaturated group that will hydrogenate with these soluble systems can be reacted to produce a predominance of one enantiomer when an optically active ligand is used. Then, the problem of achieving high efficiency becomes a purely synthetic one and is limited only by the ingenuity and skill of the chemist to make the proper ligand.We report the successful application of this principle for the preparation of optically active N-acyl-a-amino acids. Using phosphine ligands in which the phosphorus possesses asymmetry, we have been able to proceed from an initial lead of 1 5 2 5 % optical bias to 85-90% in a rational manner. The net result is a directed synthesis of chiral a-amino acids that, similar to enzymatic processes, do not require the usual resolution step.Our initial success reducing a-phenylacrylic acid with the known methylpropylphenylphosphine" as a complexing ligand gave an optical bias up to 28%.? This result encouraged us to use more complex systems, and we found that a-acylamidocinnamic acids reduced more readily with the same catalyst. A variety of tertiary phosphines gave efficiencies in the 28-32% range, as shown in TABLE 1.These results, though too low to be of practical use, did indicate that the asymmetric phosphine was integral to the catalytic process. However, we felt that further exchanging of R groups with other hydrocarbon radicals to increase

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