An efficient homogeneous catalytic enantioselective synthesis of α- amino acid derivatives

Tetrahedron Letters

Volumn 39, Issue 48, 1998, Pages 8775-8778

  O'Donnell, Martin J ^a   Delgado, Francisca ^a   Hostettler, Curt ^a,c   Schwesinger, Reinhard ^b  

^a INDIANA UNIVERSITY   (United States)

^b UNIVERSITY OF FREIBURG   (Germany)

^c ELI LILLY AND COMPANY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

AMINO ACID DERIVATIVE; BENZOPHENONE; HALIDE; PHOSPHAZENE DERIVATIVE; QUATERNARY AMMONIUM DERIVATIVE; UNCLASSIFIED DRUG;

ALKYLATION; AMINO ACID SEQUENCE; AMINO ACID SYNTHESIS; ARTICLE; CATALYSIS; CHROMATOGRAPHY; ENANTIOMER;

CINCHONA;

EID: 0032569863     PISSN: 00404039     EISSN: None     Source Type: Journal    
DOI: 10.1016/S0040-4039(98)01995-9     Document Type: Article

References (39)

1. 2. O'Donnell, M. J.; Esikova, I. A.; Mi, A.; Shullenberger, D. F.; Wu, S. "Amino Acid and Peptide Synthesis Using Phase-Transfer Catalysis," in Phase-Transfer Catalysis: Mechanisms and Synthesis (ACS Symposium Series 659), Halpern, M. E., Ed., ACS: Washington, D. C., Chapter 10, 1997.
2. 3. (a) O'Donnell, M. J.; Eckrich, T. M. Tetrahedron Lett. 1978, 4625-4628;
3. (b) O'Donnell, M. J.; Bennett, W. D.; Wu, S. J. Am. Chem. Soc. 1989, 111, 2353-2355;
4. (c) O'Donnell, M. J.; Wu, S.; Huffman, J. C. Tetrahedron 1994, 50, 4507-4518;
5. (d) O'Donnell, M. J.; Wu, S.; Esikova, I.; Mi, A. U.S. Patent, 1996 5,554,753.
6. 4. For reviews of chiral PTC, see: (a) O'Donnell, M. J. "Asymmetric Phase Transfer Reactions," in Catalytic Asymmetric Synthesis, Ojima, I., Ed., Verlag Chemie, New York, 1993, Chap. 8;
7. (b) Shioiri, T. "Chiral Phase Transfer Catalysis," in Handbook of Phase Transfer Catalysis, Sasson, Y. and Neumann, R., Eds., Blackie Academic & Professional. London, 1997, Chap. 14.
8. 5. a) Corey, E. J.; Xu, F.; Noe, M. C. J. Am. Chem. Soc. 1997, 119, 12414-12415;
9. b) Corey, E. J.; Noe, M. C.; Xu, F. Tetrahedron Lett. 1998, 39 , 5347-5350.
10. 6. Lygo, B.; Wainwright, P. G. Tetrahedron Lett. 1997, 38, 8595-8598.
11. 7. Esikova, I. A.; Nahreini, T. S.; O'Donnell, M. J. "A New Interfacial Mechanism for Asymmetric Alkylation by Phase-Transfer Catalysis," in Phase-Transfer Catalysis: Mechanisms and Synthesis (ACS Symposium Series 659), Halpern, M. E., Ed., ACS: Washington, D. C., Chapter 7. 1997.
12. 8. Schwesinger, R.; Willaredt, J.; Schlemper, H.; Keller, M.; Schmidt, D.; Fritz, H. Chem. Ber. 1994, 127, 2435-2454.
13. 9. Schwesinger bases have been used in solid-phase unnatural amino acid and peptide synthesis (termed "UPS," Unnatural Peptide Synthesis). See: (a) O'Donnell, M. J.; Zhou, C.; Scott, W. L. J. Am. Chem. Soc. 1996, 118, 6070-6072;
14. (b) Dominguez, E.; O'Donnell, M. J.; Scott, W. L. Tetrahedron Lett., 1998, 39, 2167-2170 and cited references.
15. 10. Selected references for the use of Schwesinger bases in alkylation reactions: (a) Schwesinger, R. Chimia 1985, 39, 269-272;
16. (b) Sproat, B. S.; Beijer, B.; Iribarren, A. Nucleic Acid Res. 1990, 18, 41-46;
17. (c) Schwesinger, R. Nachr. Chem. Tech. Lab. 1990, 38, 1214-1226;
18. (d) Trupp, B.; Handreck, D. -R.; Böhm, H. -P.; Knothe, L.; Fritz, H.; Prinzbach, H. Chem. Ber. 1991, 124, 1757-1775;
19. (e) Pietzonka, T.; Seebach, D. Chem. Ber. 1991, 124, 1837-1843;
20. (f) Allmendinger, T. Tetrahedron 1991, 47, 4905-4914;
21. (g) Pietzonka, T.; Seebach, D. Angew. Chem., Int. Ed. Engl. 1992, 31, 1481-1482;
22. (h) Uhlig, F.; Puschner, B.; Herrmann, E.; Zobel, B.; Bernhardt, H.; Uhlig, W. Phosphorus, Sulfur, Silicon 1993, 81, 155-163;
23. (i) Pinkos, R.; Melder, J. -P.; Weber, K.; Hunkler, D.; Prinzbach, H. J. Am. Chem. Soc. 1993, 115, 7173-7191;
24. (j) Solladié-Cavallo, A.; Csaky, A. G.; Gantz, I.; Suffert, J. J. Org. Chem. 1994, 59, 5343-5346;
25. (k) Tundo, P.; Selva, M.; Marques, C. A. ACS Symp. Ser. 1996, 81;
26. (l) Seebach, D.; Bezençon, O.; Jaun, B.; Pietzonka, T.; Matthews, J. L.; Kühnle, F. N. M.; Schweizer, W. B. Helv. Chim. Acta 1996, 79, 588-608;
27. (m) Bezençon, O.; Seebach, D. Liebigs Ann. 1996, 1259-1276;
28. (n) Jun, Z. D.; Fuchs, P. L. Tetrahedron Lett., 1996, 37, 5249-5252;
29. (o) Keynes, M. N.; Earle, M. A.; Sudharshan, M.; Hultin, P. G. Tetrahedron 1996, 52, 8685-8702;
30. (p) Du, X.; Armstrong, R. W. J. Org. Chem. 1997, 62, 5678-5679 and cited references.
31. 11. BEMP = 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine; BTPP = tert-butylimino-tri(pyrrolidino)phosphorane.
32. 12. (a) We thank Professor F. G. Bordwell and Dr. X. -M. Zhang for determining the acidity of the benzophenone imine of glycine t-butyl ester (1).
33. 3CN is 28.4 (Ref. 9) while in DMSO it is estimated to be 17.0.
34. 2Et, 22.8. See O'Donnell, M. J.; Bennett, W. D.; Bruder, W. A.; Jacobsen, W. N.; Knuth, K.; LeClef, B.; Polt, R. L.; Bordwell, F. G.; Mrozak, S. R. J. Am. Chem. Soc. 1988, 110, 8520-8525.
35. 2 (0.5 mL). The reaction mixture was then cooled (-50 or -78 °C), the base was added (1.5 equiv. for active halides, 5.0 equiv. for non-active halides) dropwise over a few seconds, and the reaction mixture was stirred at -50 or -78 °C until starting material 1 had been consumed (TLC, silica gel, hexane/EtOAc, 12:1). The solvent was evaporated in vacuo and the residue was purified by flash chromatography on silica gel. (hexane/EtOAc, 12:1). Chiral HPLC (isocratic) was used to determine enantioselectivities using the following (column, mobile phase (ranges used), flow rate (ranges used), detection wavelength, compounds): Baker Bond DNBPG (covalent), hexane-iPrOH (600:1 to 350:1), 0.3 mL/min, 254 nm, 2b, 2c, 2d, 2e, 2f, 2h, 2n, 2o); Chiracel OD, hexane:iPrOH (99.5:0.5), 1.0 mL/min, 254 nm, 2a, 2g; Whelk-01, hexane:iPrOH (98:2 to 90:10), 1.0 to 0.6 mL/min, 254 nm, 2i, 2j, 2k, 2l, 2m, 2p.
36. 15. A temperature study of the alkylation of an active halide (benzyl bromide) with BEMP (3) under normal reaction conditions using catalyst 5 follows (alkylation temperature, time, yield of 2, %ee): -78 °C., 7h, 88%, 91%ee; -50 °C., 5h, 89%, 83%ee; -20 °C, 88%, 77%ee; RT, 89%, 48%ee.
37. 16. A temperature study of the alkylation of a non-active halide (ethyl iodide) with BTPP (4) under normal reaction conditions using catalyst 5 follows (alkylation temperature, time, yield of 2, %ee): -78 °C., 24h, 84%, 93%ee; -50 °C., 6h, 89%, 89%ee; -20 °C., 89%, 87%ee; RT, 88%, 59%ee.
38. 17. Compared with the optimal conditions (see notes 15 and 16), the stronger base BTPP with an active halide (benzyl bromide) gave a reduced enantioselectivity (-50 °C., 4h, 91%, 81%ee) (-78 °C., 4h, 86%, 88%ee) while the weaker base BEMP with a non-active halide (ethyl iodide) resulted in a much slower reaction (-50 °C., 24h, 78%, 91%ee) (-78 °C., 24h, 63%+starting Schiff base, 93%ee).
39. 18. Reaction with the secondary halide, isopropyl iodide, was not successful. Similarly, reaction with benzhydryl bromide under standard conditions did not yield alkylation product.