Preparation and use in amino acid synthesis of a new chiral glycine derivative - (R)- and (S)-tert-Butyl 2-tert-Butyl-4-methoxy-2,5-dihydroimidazole-1-carboxylate (BDI)

European Journal of Organic Chemistry

Volumn , Issue 7, 1998, Pages 1337-1351

  Seebach, Dieter ^a   Hoffmann, Matthias ^a  

^a ETH ZURICH   (Switzerland)

Author keywords

Amino acid synthesis; Chiral glycine building block; Dihydroimidazole

Indexed keywords

EID: 0002478426     PISSN: 1434193X     EISSN: None     Source Type: Journal    
DOI: 10.1002/(SICI)1099-0690(199807)1998:7<1337::AID-EJOC1337>3.0.CO;2-T     Document Type: Article

References (54)

1. R. M. Williams, Synthesis of Optically Active α-Amino Acids, 1st ed., Pergamon Press, Oxford, 1989. - R. O. Duthaler, Tetrahedron 1994, 50, 1539-1650. For a most recent paper on amino acid synthesis by the O'Donnel methodology see: E. J. Corey, F. Xu, M. C. Noe, J. Am. Chem Soc. 1997, 119, 12414.
2. R. M. Williams, Synthesis of Optically Active α-Amino Acids, 1st ed., Pergamon Press, Oxford, 1989. - R. O. Duthaler, Tetrahedron 1994, 50, 1539-1650. For a most recent paper on amino acid synthesis by the O'Donnel methodology see: E. J. Corey, F. Xu, M. C. Noe, J. Am. Chem Soc. 1997, 119, 12414.
3. R. M. Williams, Synthesis of Optically Active α-Amino Acids, 1st ed., Pergamon Press, Oxford, 1989. - R. O. Duthaler, Tetrahedron 1994, 50, 1539-1650. For a most recent paper on amino acid synthesis by the O'Donnel methodology see: E. J. Corey, F. Xu, M. C. Noe, J. Am. Chem Soc. 1997, 119, 12414.
4. U. Schöllkopf, Tetrahedron 1983, 39, 2085-2091. - U. Schöllkopf, Pure & Appl. Chem. 1983, 55, 1799-1806. - U. Schöllkopf in Topics in Current Chemistry (Ed.: F. L. Boschke), Springer Verlag, Berlin, 1983, vol. 109, p. 65-85.
5. U. Schöllkopf, Tetrahedron 1983, 39, 2085-2091. - U. Schöllkopf, Pure & Appl. Chem. 1983, 55, 1799-1806. - U. Schöllkopf in Topics in Current Chemistry (Ed.: F. L. Boschke), Springer Verlag, Berlin, 1983, vol. 109, p. 65-85.
6. U. Schöllkopf, Tetrahedron 1983, 39, 2085-2091. - U. Schöllkopf, Pure & Appl. Chem. 1983, 55, 1799-1806. - U. Schöllkopf in Topics in Current Chemistry (Ed.: F. L. Boschke), Springer Verlag, Berlin, 1983, vol. 109, p. 65-85.
7. ⋯with recycling of the undesired enantiomer[4][5][6].
8. R. Fitzi, D. Seebach, Tetrahedron 1988, 44, 5277-5292.
9. Review: D. Seebach, A. R. Sting, M. Hoffmann. Angew. Chem. 1996, 108, 2880-2921; Angew. Chem. Int. Ed. 1996, 35, 2708-2748.
10. Review: D. Seebach, A. R. Sting, M. Hoffmann. Angew. Chem. 1996, 108, 2880-2921; Angew. Chem. Int. Ed. 1996, 35, 2708-2748.
11. J. N. Kinkel, U. Gysel, D. Blaser, D. Seebach, Helv. Chim. Acta 1991, 74, 1622-1635. - D. Blaser, D. Seebach, Liebigs Ann. Chem. 1991, 1067-1078. - D. Seebach, T. Gees, F. Schuler, Liebigs Ann Chem. 1993, 785-799.
12. J. N. Kinkel, U. Gysel, D. Blaser, D. Seebach, Helv. Chim. Acta 1991, 74, 1622-1635. - D. Blaser, D. Seebach, Liebigs Ann. Chem. 1991, 1067-1078. - D. Seebach, T. Gees, F. Schuler, Liebigs Ann Chem. 1993, 785-799.
13. J. N. Kinkel, U. Gysel, D. Blaser, D. Seebach, Helv. Chim. Acta 1991, 74, 1622-1635. - D. Blaser, D. Seebach, Liebigs Ann. Chem. 1991, 1067-1078. - D. Seebach, T. Gees, F. Schuler, Liebigs Ann Chem. 1993, 785-799.
14. Preliminary communication: S. Blank, D. Seebach, Angew. Chem. 1993, 105, 1780-1781; Angew. Chem. Int. Ed. 1993, 32, 1765-1766.
15. Preliminary communication: S. Blank, D. Seebach, Angew. Chem. 1993, 105, 1780-1781; Angew. Chem. Int. Ed. 1993, 32, 1765-1766.
16. Abstract of a poster: M. Hoffmann, D. Seebach, Chimia 1997, 51, 90-92.
17. M. Hoffmann, S. Blank, D. Seebach, E. Küsters, E. Schmid, Chirality 1998, 10, 217-222.
18. D. Seebach, M. Hoffmann, A. R. Sting, J. N. Kinkel, M. Schulte, E. Küsters, J. Chromatogr. A 1998, 796, 299-307.
19. S. Blank, Diss. ETH Nr. 10193, Zürich, Switzerland, 1993.
20. ⋯mainly due to the fact that it was difficult to exceed enantiomer ratios above 97:3.
21. M. Hoffmann, Diss. ETH Nr. 12387, Zürich, Switzerland, 1997.
22. The absolute configuration of (R)- and (S)-1 was determined from the X-ray crystal structure of the salt 3 (P. Seiler, X-ray service of our laboratory)[11]. It also follows from the comparison of amino acid esters, synthesized from BDI, with authentic enantiopure samples of known configuration.
23. For the isolation and characterization of the racemic as well as of the enantiopure (Z)-analogs of 2 and of BDI see ref.[10].
24. Most mono- and dialkylated BDI derivatives are oils which may partially decompose upon distillation. The yields given in Scheme 3 and 5 refer to analytically pure chromatographed samples.
25. The structure of enantiopure 14 (Scheme 3) with p-nitrobenzyl instead of p-methoxybenzyl as the substituent was determined by B. Rheiner, as part of the requirements in a crystallography course at ETH Zürich, 1992.
26. With Li-Boc-BMI, Fitzi had obtained the product of alkylation with rac-1-phenylethylbromide in 68% yield and with a diastereoisomer ratio of 92.5:7.5[4]; see the mechanistic discussion in footnote 43 of [19]. For another enantiomer differentiation of an alkyl halide by a chiral oxazoline see: A. I. Meyers, K. Kamata, J. Am Chem. Soc. 1976, 98, 2290-2294.
27. K. Suzuki, D. Seebach, Liebigs Ann. Chem. 1992, 51-61.
28. Various amounts and concentrations of hydrochloric acid, trifluoro acetic acid (TFA) and acidic ion exchange resin in aqueous methanol, aqueous THF and water were tested.
29. Y. Hamada, S. Kato, T. Shioiri, Tetrahedron Lett. 1985, 26, 3223-3226.
30. 3Si-protection under the conditions of introducing the (Z) group. Only the amino acid ester rac-16 could be obtained in analytically pure form as such (bulb-to-bulb destillation at high vacuum). A protection of the amino functionality followed by flash chromatography was therefore not necessary in this case. In all other cases (also with the α-branched amino acid esters shown in Scheme 6) the (Z) protecting group was introduced in order to obtain analytically pure samples of the esters F and H.
31. Formation of diketopiperazines by dimerization of amino acid methyl esters F was not observed. The poor overall yields of (Z)-protected esters (see Experimental Part) is partially due to losses caused by water-solubility of the esters F.
32. L-Alanine, L-valine, and L-phenylalanine methyl ester (as obtained from (S)-(+)-BDI) were characterized by gas chromalography following the literature procedure: S. Abdalla, E. Bayer, H. Frank, Chromatographia 1987, 23, 83-85.
33. 3 (5-epi-24) was determined by B. Rheiner, as part of the requirements in a crystallography course at ETH Zürich, 1992.
34. The methodology of using BDI as a chiral building block in amino acid synthesis clearly employs milder hydrolysis conditions than all the other methods developed in our group, so far, and also than many other synthetic methods found in the literature (for an overview see ref. [1][5]).
35. D. Seebach, E. Pfammatter, V. Gramlich, T Bremi, F. Kühnle, S. Portmann, I. Tironi, Liebigs. Ann. Chem. 1992, 1145-1151.
36. For results and a detailed mechanistic discussion of Michael additions to di-tert-butylphenol esters see ref.[19] and references to Heathcock's and Cooke's work therein.
37. See also our other papers on carbonyl derivatives with "sterically protected but electronically active" CO groups, reference 10 in ref.[19].
38. At this temperature pivalaldehyde reacted very slowly with enaminate E, giving rise to the product rac-44 in only 8% yield.
39. For erythro-hydroxyleucine see ref.[32] and for erythro-hydroxyphenylalanine see ref.[33].
40. K. J. Hale, S. Manaviazar, V. M. Delisser, Tetrahedron 1994, 50, 9181-9188.
41. A. Saeed, D. W. Young, Tetrahedron 1992, 48, 2507-2514.
42. For other methods developed by our group to prepare α-amino β-hydroxy acids of erythro configuration see: D. Seebach, E. Juaristi, D. D. Miller, C. Schickli, T. Weber, Helv. Chim. Acta 1987, 70, 237-261 and S. Blank, D. Seebach, Liebigs Ann. Chem. 1993, 889-896.
43. For other methods developed by our group to prepare α-amino β-hydroxy acids of erythro configuration see: D. Seebach, E. Juaristi, D. D. Miller, C. Schickli, T. Weber, Helv. Chim. Acta 1987, 70, 237-261 and S. Blank, D. Seebach, Liebigs Ann. Chem. 1993, 889-896.
44. The two diastereomeric Li-alkoxides formed in the original addition step are expected to cyclize with different rates, and, indeed, the ratios of epimers detected in the two types of products 43-46 and 47-50 are different.
45. H. E. Zimmerman, M. D. Traxler, J. Am. Chem Soc. 1957, 79, 1920-1923.
46. D. Blaser, S. Y. Ko, D. Seebach, J. Org. Chem. 1991, 56, 6230-6233
47. and D. Blaser, Diss. ETH Nr. 9527, Zürich, Switzerland, 1991.
48. For a detailed mechanistic discussion see refs.[5][9], and: D. Seebach, T. Maetzke, W. Petter, B. Klötzer, D. A. Plattner, J. Am. Chem. Soc 1991, 113, 1781-1786.
49. 2R group[38].
50. This electrophile was prepared according to the experimental procedure described on page 66 in: L. Brandsma, H. D. Verkruijsse, Synthesis of Acetylenes, Allenes and Cumulenes - A Laboratory Manual, Elsevier, Amsterdam, 1981.
51. This electrophile was prepared in analogy with the experimental procedure for the preparation of 3-bromocyclohexene described on page 401 in: A. Vogel, Textbook of Practical Organic Chemistry, Longman, New York, 1978.
52. For the preparation of this electrophile see ref.[41]
53. A. Studer, D. Seebach, Liebigs Ann Chem. 1995, 217-222.
54. M. P. Cooke, J. Org. Chem. 1986, 51, 1637-1638.