Catalytic asymmetric hydrogenation of β-substituted α,β,γ,δ- unsaturated amino acids

Tetrahedron Letters

Volumn 40, Issue 16, 1999, Pages 3093-3096

  Burk, Mark J ^a,b   Bedingfield, Karen M ^a,c   Kiesman, William F ^a,d   Allen, John G ^a  

^a DUKE UNIVERSITY   (United States)

^b Chirotech Technology Limited   (United Kingdom)

^c BRISTOL MYERS SQUIBB   (United States)

^d BIOGEN   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AMINO ACID DERIVATIVE; GLYCINE DERIVATIVE;

ARTICLE; CATALYSIS; HYDROGENATION; REACTION ANALYSIS; STEREOCHEMISTRY;

EID: 0033574553     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(99)00437-2     Document Type: Article

References (19)

1. (a) Burk, M. J.; Gross, M. F.; Harper, T. G. P.; Kalberg, C. S.; Lee, J. R.; Martinez, J. P. Pure & Appl. Chem. 1996, 68, 37 and references therein,
2. (b) Burk, M. J.; Bienewald, F. "Unnatural α-Amino acids via asymmetric hydrogenation of enamides," in Transition Metals for Organic Synthesis and Fine Chemicals; C. Bolm and M. Beller Eds. Wiley VCH: Wienheim, 1998; Chapter 1, pp. 13-25.
3. For the synthesis of dienamide substrates, please see Burk, M. J.; Allen, J. G.; Kiesman, W. F.; Stoffan, K. M. Tetrahedron Lett. 1997, 38, 1309.
4. Abbreviations: DuPHOS 1,2-bis(phospholano)benzene; BPE 1,2-bis(phospholano)ethane.
5. Burk, M. J.; Allen, J. G.; Kiesman, W. F. J. Am. Chem. Soc. 1998, 120, 657.
6. (a) Halpern, J. In Asymmetric Synthesis; Morrison, J. D.; Ed.; Academic Press: New York, 1985; Vol. 5, Chapter 2.
7. (b) Landis, C. R.; Halpern, J. J. Am. Chem. Soc. 1987, 109, 1746.
8. (c) Nagel, U.; Rieger, B. Organometallics 1989, 8, 1534.
9. (d) Ojima, I.; Kogure, T.; Yoda, N. J. Org. Chem. 1980, 45, 4728.
10. (e) Brown, J. M.; Chaloner, P. A. J. Chem. Soc., Chem. Commun. 1980, 344.
11. (f) Brown, J. M.; Murrer, B. A. J. Chem.. Soc., Perkin Trans. II 1982, 489.
12. (g) Chan, A. S. C.; Pluth, J. J.; Halpern, J. J. Am. Chem. Soc. 1980, 102, 5952.
13. (a) Burk, M. J.; Gross, M. F.; Martinez, J. P. J. Am. Chem. Soc. 1995, 117, 9375.
14. See also (b) Hoerrner, R. S.; Askin, D.; Volante, R. P.; Reider, P. J. Tetrahedron Lett. 1998, 39, 3455.
15. R = 6.51 minutes.
16. All substrates and hydrogenated products gave satisfactory characterization data.
17. Preliminary results show that heating the reaction mixtures to 50-60 °C greatly improves reaction rate and substrate conversion without significantly diminishing stereoselectivity.
18. We proposed that stereoselectivity in the overreduction reaction took place due to double differentiation between the asymmetric catalyst and chiral monoreduced product. Where the major 4/6 enantiomer was the favored substrate for the overreduction reaction, the enantiomeric excess of 4/6 remaining would be expected to fall.
19. When (R,R)- and (S,S)-enantiomers of the same catalyst were used to give both enantiomeric products, the %ee's achieved were essentially identical, as is indicated in Scheme 2 for the most enantioselective catalyst, Me-BPE-Rh.