The manual and automated solid-phase synthesis of α-substituted prolines and homologues

Journal of Combinatorial Chemistry

Volumn 5, Issue 5, 2003, Pages 684-692

  Scott, William L ^a,b   Alsina, Jordi ^b   O'Donnell, Martin J ^b  

^a ELI LILLY AND COMPANY   (United States)

^b INDIANA UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ALKANE DERIVATIVE; PROLINE DERIVATIVE;

ALKYLATION; AMINO TERMINAL SEQUENCE; ARTICLE; AUTOMATION; MOLECULAR INTERACTION; RACEMIC MIXTURE; SOLID;

EID: 0141795447     PISSN: 15204766     EISSN: None     Source Type: Journal    
DOI: 10.1021/cc030037q     Document Type: Article

References (47)

1. The trans/cis notation refers to the relationship between the two peptide bond side chains and ignores the higher priority of the carbonyl group. See: Abell, A. D.; Gardiner, J. J. Org. Chem. 1999, 64, 9668-9672.
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5. (d) Gillespie, P.; Cicariello, J.; Olson, G. L. Biopolymers (Peptide Science) 1997, 43, 191-217.
6. Holladay, M. W.; Nadzan, A. M. J. Org. Chem. 1991, 56, 3900-3905.
7. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
8. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
9. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
10. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
11. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
12. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
13. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
14. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
15. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
16. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
17. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
18. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
19. For reports in the solid-phase synthesis of similar targets, see: (a) Murphy, M. M.; Schullek, J. R.; Gordon, E. M.; Gallop, M. A. J. Am. Chem. Soc. 1995, 117, 7029-7030. (b) Bicknell, A. J.; Hird, N. W. Bioorg. Med. Chem. Lett. 1996, 6, 2441-2444. (c) Hamper, B. C.; Dukesherer, D. R.; South, M. S. Tetrahedron Lett. 1996, 37, 3671-3674. (d) Hollinshead, S. P. Tetrahedron Lett. 1996, 37, 9157-9160. (e) Maclean, D.; Schullek, J. R.; Murphy, M. M.; Ni, Z.-J. ; Gordon, E. M.; Gallop, M. A. Proc. Natl. Acad. Sci. U.S.A. 1997, 94, 2805-2810. (f) Gong, Y.-D.; Najdi, S.; Olmstead, M. M.; Kurth, M. J. J. Org. Chem. 1998, 63, 3081-3086. (g) Karoyan, P.; Triolo, A.; Nannicini, R.; Giannotti, D.; Altamura, M.; Chassaing, G.; Perrotta, E. Tetrahedron Lett. 1999, 40, 71-74. (h) Dondas, H. A.; Grigg, R.; MacLachlan, W. S.; MacPherson, D. T.; Markandu, J.; Sridharan, V.; Suganthan, S. Tetrahedron Lett. 2000, 41, 967-970. (i) Henkel, B.; Stenzel, W.; Schotten, T. Bioorg. Med. Chem. Lett. 2000, 10, 975-977. (j) Barrett, A. G. M.; Boffey, R. J.; Frederiksen, M. U.; Newton, C. G.; Roberts, R. S. Tetrahedron Lett. 2001, 42, 5579-5581. (k) Hoveyda, H. R.; Hall, D. G. Org. Lett. 2001, 3, 3491-3494. (1) Steger, M.; Hubschwerlen, C.; Schmid, G. Bioorg. Med. Chem. Lett. 2001, 11, 2537-2540. (m) Hanessian, S.; Bayrakdarian, M. Tetrahedron Lett. 2002, 43, 9441-9444.
20. (a) Cativiela, C.; Díaz-de-Villegas, M. D. Tetrahedron: Asymmetry 2000, 11, 645-732.
21. (b) Park, K.-H.; Kurth, M. J. Tetrahedron 2002, 58, 8629-8659.
22. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
23. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
24. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
25. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
26. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
27. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
28. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
29. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
30. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
31. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
32. For selected reports in the asymmetric solution phase preparation of α-substituted proline ring homologues, see ref 3 and: (a) Seebach, D.; Boes, M.; Naef, R.; Schweizer, W. B. J. Am. Chem. Soc. 1983, 105, 5390-5398. (b) Joucla, M.; El Goumzili, M. Tetrahedron Lett. 1986, 27, 1681-1684. (c) Bajgrowicz, J.; El Achquar, A.; Roumestant, M.-L.; Pigière, C.; Viallefont, P. Heterocycles 1986, 24, 2165-2167. (d) Schöllkopf, U.; Hinrichs, R.; Lonsky, R. Angew. Chem., Int. Ed. Engl. 1987, 26, 143-145. (e) Seebach, D.; Dziadulewicz, E.; Behrendt, L.; Cantoreggi, S.; Fitzi, R. Liebigs Ann. Chem. 1989, 1215-1232. (f) Berrien, J.-F.; Royer, J.; Husson, H.-P. J. Org. Chem. 1994, 59, 3769-3774. (g) Ferey, V.; Vedrenne, P.; Toupet, L.; Le Gall, T.; Mioskowski, C. J. Org. Chem. 1996, 61, 7244-7245. (h) Matsumura, Y.; Kinoshita, T.; Yanagihara, Y.; Kanemoto, N.; Watanabe, M. Tetrahedron Lett. 1996, 37, 8395-8398. (i) Chinchilla, R.; Galindo, N.; Nájera, C. Tetrahedron: Asymmetry 1998, 9, 2769-2772. (j) Wang, H.; Germanas, J. P. Synlett 1999, 33-36. (k) Abellán, T.; Chinchilla, R.; Galindo, N.; Guillena, G.; Nájera, C.; Sansano, J. M. Eur. J. Org. Chem. 2000, 2689-2697.
33. Scott, W. L.; O'Donnell, M. J.; Delgado, F.; Alsina, J. J. Org. Chem. 2002, 67, 2960-2969.
34. (a) O'Donnell, M. J.; Zhou, C.; Scott, W. L. J. Am. Chem. Soc. 1996, 118, 6070-6071.
35. (b) Scott, W. L.; Zhou, C.; Fang, Z.; O'Donnell, M. J. Tetrahedron Lett. 1997, 38, 3695-3698.
36. For a recent short review about UPS chemistry, see: (c) O'Donnell, M. J. ; Scott, W. L. Unnatural Amino Acid and Peptide Synthesis (UPS). In Peptides 2000: Proceedings of the Twenty-Sixth European Peptide Symposium; Martinez, J., Fehrentz, J.-A., Eds.; EDK: Paris, 2001; pp 31-36.
37. Schwesinger, R.; Willaredt, J.; Schlemper, H.; Keller, M.; Schmitt, D.; Fritz, H. Chem. Ber. 1994, 127, 2435-2454.
38. The following abbreviations are used: BTPP, tert-butylimino-tri(pyrrolidino)phosphorane; DIEA, N,N-diisopropylethylamine; FAB-MS, fast atom bombardment mass spectrometry; Fmoc, 9-fluorenylmethoxycarbonyl; Fmoc-Cl, 9-fluorenylmethyl chloroformate; HOAc, acetic acid; UPS, unnatural peptide synthesis; TES, triethylsilane; TMOF, trimethyl orthoformate.
39. For example, the presence of cross-linked side products was minimized during the alkylation by using a 10-fold excess of α-bromo-ω -chloroalkanes. In another example of a side reaction, when n = 3, there was evidence that the ω-bromo compound led to partial olefin formation by elimination.
40. For the conversion of an unreactive alkyl chloride into the more reactive iodide by an in situ Finklestein reaction, see: O'Donnell, M. J.; Lugar, C. W.; Pottorf, R. S.; Zhou, C.; Scott, W. L.; Cwi, C. L. Tetrahedron Lett. 1997, 38, 7163-7166.
41. Pearson, D. A.; Blanchette, M.; Baker, M. L.; Guindon, C. A. Tetrahedron Lett. 1989, 30, 2739-2742.
42. For selected reports concerning the asymmetric solution-phase synthesis of 3-alkyl-tetrahydroisoquinoline-3-carboxylic acid derivatives, see ref 6d, 6k, and: Ooi, T.; Takeuchi, M.; Maruoka, K. Synthesis 2001, 1716-1718.
43. Early experiments involved use of α,α′ -dibromo-o-xylene as the alkylating agent, which led to considerably lower crude HPLC purities and yields.
44. For n = 2 with strategy 2, the desired four-membered ring was not obtained; neither was N-acylated chloro-substituted starting material 8 recovered. We believe there is a competing intramolecular cyclization by O-alkylation from 8 to generate a six-membered imidate.
45. 2O (95:5) in order to minimize partial decomposition of the N-acylated final products over time. Unacylated material resulting from the acid-catalyzed hydrolysis can be inferred by the presence of 2-naphthoic acid in the HPLC of the crude products.
46. Reverse O- to N-acyl migration can be accomplished by allowing the O-acyl product to stand in acetonitrile in the presence of DIEA overnight to complete the conversion to the N-acyl desired product. For a report of a similar O- to N-acyl migration under basic conditions, see: Owens, T. D.; Semple, J. E. Org. Lett. 2001, 3, 3301-3304.
47. Lewis, A.; Wilkie, J.; Rutherford, T. J.; Gani, D. J. Chem. Soc., Perkin Trans. 1, 1998, 3777-3793.