Stereocontrolled total synthesis of (+)-paraherquamide B

Journal of the American Chemical Society

Volumn 118, Issue 3, 1996, Pages 557-579

  Cushing, Timothy D ^a,c   Sanz Cervera, Juan F ^a,b   Williams, Robert M ^a  

^a Department of Environmental and Radiological Health Sciences   (United States)

^b UNIVERSITY OF VALENCIA   (Spain)

^c AMGEN INC   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ANTHELMINTIC AGENT; PARAHERQUAMIDE B; PARAHERQUAMIDE DERIVATIVE; UNCLASSIFIED DRUG;

ARTICLE; DRUG SYNTHESIS; REACTION ANALYSIS; STEREOCHEMISTRY;

EID: 0030020574     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja952666c     Document Type: Article

References (115)

1. (a) Yamazaki, M.; Fujimoto, H.; Okuyama, E.; Ohta, Y. Proc. Jpn. Assoc. Mycotoxicol. 1980, 10, 27.
2. (b) Yamazaki, M.; Okuyama, E.; Kobayashi, M.; Inoue, H. Tetrahedron Lett. 1981, 22, 135.
3. (a) Blizzard, T. A.; Marino, G.; Mrozik, H.; Fisher, M. H.; Hoogsteen, K.; Springer, J. P. J. Org. Chem. 1989, 54, 2657.
4. (b) Blizzard, T. A.; Mrozik, H.; Fisher, M. H.; Schaeffer, J. M. J. Org. Chem. 1990, 55, 2256.
5. (c) Blizzard, T. A.; Margiatto, G.; Mrozik, H.; Schaeffer, J. M.; Fisher, M. H. Tetrahedron Lett. 1991, 32, 2437.
6. (d) Blizzard, T. A.; Margiatto, G.; Mrozik, H.; Schaeffer, J. M.; Fisher, M. H. Tetrahedron Lett. 1991, 32, 2441.
7. (e) Blizzard, T. A.; Rosegay, A.; Mrozik, H.; Fisher, M. H. J. Labelled Compd. Radiopharm. 1990, 28, 461.
8. (a) Ondeyka, J. D.; Goegelman, R. T.; Schaeffer, J. M.; Kelemen, L. J. Antibiot. 1990, 43, 1375.
9. (b) Liesch, J. M.; Wichman, C. F. J. Antibiot. 1990, 43, 1380.
10. Blanchflower, S. E.; Banks, R. M.; Everett, J. R.; Manger, B. R.; Reading, C. J. Antibiot. 1991, 44, 492.
11. Blanchflower, S. E.; Banks, R. M.; Everett, J. R.; Reading, C. J. Antibiot. 1993, 46, 1355.
12. Ostlind, D. A.; Mickle, W. G.; Ewanciw, D. V.; Andriuli, F. J.; Campbell, W. C.; Hernandez, S.; Mochaeles, S.; Munguira, E. Res. Vet. Sci. 1990, 48, 260.
13. (a) Shoop, W. L.; Egerton, J. R.; Eary, C. H.; Suhayda, D. J. Parasitol. 1990, 76 (2) 186.
14. (b) Shoop, W. L.; Michael, B. F.; Haines, H. W.; Eary, C. H. Vet. Parasitol. 1992, 43, 259.
15. (c) Schaeffer, J. M.; Blizzard, T. A.; Ondeyka, J.; Goegelman, R.; Sinclair, P. J.; Mrozik, H. Biochem. Pharmacol. 1992, 43, 679.
16. (d) Shoop, W. L.; Haines, H. W.; Eary, C. H.; Michael, B. F. Am. J. Vet. Res. 1992, 53, 2032.
17. Coles, G. C. Pestic. Sci. 1977, 8, 536.
18. (a) Van Wyk, J. A.; Malan, F. S. Vet. Rec. 1988, 123, 226.
19. (b) Echevarria, F. A. M.; Trindade, N. P. Vet. Rec. 1989, 124, 147.
20. (a) Sanz-Cervera, J. F.; Glinka, T.; Williams, R. M. J. Am. Chem. Soc. 1993, 115, 347.
21. (b) Sanz-Cervera, J. F.; Glinka, T.; Williams, R. M. Tetrahedron 1993, 49, 8471.
22. (a) Williams, R. M.; Glinka, T.; Kwast, E. J. Am. Chem. Soc. 1988, 110, 5927.
23. (b) Williams, R. M.; Glinka, T.; Kwast, E.; Coffman, H.; Stille, J. K. J. Am. Chem. Soc. 1990, 112, 808.
24. (c) Williams, R. M.; Glinka, T.; Kwast, E. Tetrahedron Lett. 1989, 30, 5575.
25. A preliminary account of this work has appeared: Cushing, T. D.; Sanz-Cervera, J. F.; Williams, R. M. J. Am. Chem. Soc. 1993, 115, 9323.
26. (a) Birch, A. J.; Wright, J. J. J. Chem. Soc., Chem. Commun. 1969, 644.
27. (b) Birch, A. J.; Wright, J. J.; Tetrahedron 1970, 26, 2339.
28. (c) Birch, A. J.; Russell, R. A. Tetrahedron 1972, 28, 2999.
29. (d) Baldas J.; Birch, A. J.; Russell, R. A. J. Chem. Soc., Perkin Trans. I 1974, 50.
30. (a) Polonsky, J.; Merrien, M. A.; Prange, T; Pascard, C. J. Chem Soc., Chem Commun. 1980, 601.
31. (b) Prange, T.; Billion, M.-A.; Vuilhorgne, M.; Pascard, C.; Polonsky, J. Tetrahedron Lett. 1981, 22, 1977.
32. Bond, R. F.; Boeyens, J. C. A.; Holzapfel, C. V.; Steyn, P. S. J. Chem. Soc., Perkin Trans. I 1979, 1751.
33. Fredenhagen, A.; Hug, P.; Peter, H. H. J. Antibiot. 1990, 48, 661.
34. The enantiomer of the natural product was selected as the target due to the large relative cost difference between (S)- and (R)-proline.
35. (a) Somei, M.; Karasawa, Y.; Kaneko, C. Heterocycles 1981, 16, 941.
36. (b) Kametani, T.; Kanaya, N.; Ihara, M. J. Am. Chem. Soc. 1980, 102, 3974.
37. (a) Stoermer, D.; Heathcock, C. H. J. Org. Chem. 1993, 58, 564.
38. (b) Guller, R.; Dobler, M.; Borschberg, H.-J. Helv. Chim. Acta 1991, 74, 1636.
39. (c) Darbre, T.; Nussbaumer, C.; Borschberg, H.-J. Helv. Chim. Acta 1984, 67, 1040.
40. (d) Delpech, B.; Khuong-Huu, Q. J. Org. Chem. 1978, 43, 4898.
41. Guillaumet, G.; Coudert, G.; Loubinnoux, B. Angew. Chem., Int. Ed. Engl. 1983, 22, 64. (Matrix Presented)
42. Williams, R. M.; Cushing, T. D. Tetrahedron Lett. 1990, 31, 6325.
43. (a) Nicolaou, K. C. Tetrahedron 1981, 37, 4097.
44. (b) Nicolaou, K. C.; Magolda, R. L.; Sipio, W. J.; Barnette, W. E.; Lysenko, Z.; Joullie, M. M. J. Am. Chem. Soc. 1980, 102, 3784.
45. (c) Clive, D. L. J. Tetrahedron 1978, 34, 1049-1132.
46. (a) Clive, D. J. L.; Chiiattu, G.; Curtis, N. J.; Kiel, W. A.; Wong, C. K. J. Chem. Soc., Chem. Commun. 1977, 725.
47. See also: (b) Liotta, D.; Zima, G. Tetrahedron Lett. 1978, 50, 4977. (c) Tiecco, M.; Testaferri, L.; Tingoli, M.; Bartoli, D.; Balducci, R. J. Org. Chem. 1990, 55, 429.
48. See also: (b) Liotta, D.; Zima, G. Tetrahedron Lett. 1978, 50, 4977. (c) Tiecco, M.; Testaferri, L.; Tingoli, M.; Bartoli, D.; Balducci, R. J. Org. Chem. 1990, 55, 429.
49. Nicolaou, K. C.; Claremon, D. A.; Barnette, W. E.; Seitz, S. P. J. Am. Chem. Soc. 1979, 101, 3704.
50. (a) Cookson, R. C.; Liverton, N. J. J. Chem. Soc., Perkin Trans. I 1985, 1589.
51. (b) Kocienski, P.; Love, C.; Whitby, R.; Roberts, D. A. Tetrahedron Lett. 1988, 29, 2867. See also:
52. (c) Nicolaou, K. C.; Prasad, C. V. C.; Somers, P. K.; Hwang, C.-K. J. Am. Chem. Soc. 1989, 111, 5335.
53. For a related observation, see: Taylor, S. T.; Davisson, M. E.; Hissom, B. R., Jr.; Brown, S. J.; Pristach, H. A.; Schramm, S. B.; Harvey, S. M. J. Org. Chem. 1987, 52, 425.
54. Hutchins, R. O.; Hutchins, M. G.; Milewski, C. A. J. Org. Chem. 1972, 37, 4191.
55. Houlihan, W. J.; Remers, W. A.; Brown, R. K. Indoles, Part one, The Chemistry of Heterocycles; John Wiley & Sons, Inc.: New York, 1972.
56. (a) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483.
57. (b) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431.
58. This difficulty was observed in a short synthesis of the known 6-acetoxy-7-methoxyindole (i). The unstable substance i was treated with TMSI, producing the dimer ii as the sole product. (Matrix Presented) See: (a) Walker, G. N. J. Am. Chem. Soc. 1955, 77, 3844. (b) Burton, H.; Duffield, J. A.; Prail, P. F. G. J. Chem. Soc. 1950, 1062. (c) Beer, R. J. S.; Mcgrath, L.; Robertson, A.; Woodier, A. B. J. Chem. Soc. 1949, 2061. (d) Beer, R. J S.; Clarke, K.; Khorana, H. G.; Robertson, A. J. Chem. Soc. 1948, 2223. (e) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483. (f) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431. (g) Deibel, R. M. B.; Chedekel, M. R. J. Am. Chem. Soc. 1984, 106, 5884. (h) Heacock, R. A. Chem. Rev. 1959, 59, 181.
59. This difficulty was observed in a short synthesis of the known 6-acetoxy-7-methoxyindole (i). The unstable substance i was treated with TMSI, producing the dimer ii as the sole product. (Matrix Presented) See: (a) Walker, G. N. J. Am. Chem. Soc. 1955, 77, 3844. (b) Burton, H.; Duffield, J. A.; Prail, P. F. G. J. Chem. Soc. 1950, 1062. (c) Beer, R. J. S.; Mcgrath, L.; Robertson, A.; Woodier, A. B. J. Chem. Soc. 1949, 2061. (d) Beer, R. J S.; Clarke, K.; Khorana, H. G.; Robertson, A. J. Chem. Soc. 1948, 2223. (e) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483. (f) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431. (g) Deibel, R. M. B.; Chedekel, M. R. J. Am. Chem. Soc. 1984, 106, 5884. (h) Heacock, R. A. Chem. Rev. 1959, 59, 181.
60. This difficulty was observed in a short synthesis of the known 6-acetoxy-7-methoxyindole (i). The unstable substance i was treated with TMSI, producing the dimer ii as the sole product. (Matrix Presented) See: (a) Walker, G. N. J. Am. Chem. Soc. 1955, 77, 3844. (b) Burton, H.; Duffield, J. A.; Prail, P. F. G. J. Chem. Soc. 1950, 1062. (c) Beer, R. J. S.; Mcgrath, L.; Robertson, A.; Woodier, A. B. J. Chem. Soc. 1949, 2061. (d) Beer, R. J S.; Clarke, K.; Khorana, H. G.; Robertson, A. J. Chem. Soc. 1948, 2223. (e) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483. (f) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431. (g) Deibel, R. M. B.; Chedekel, M. R. J. Am. Chem. Soc. 1984, 106, 5884. (h) Heacock, R. A. Chem. Rev. 1959, 59, 181.
61. This difficulty was observed in a short synthesis of the known 6-acetoxy-7-methoxyindole (i). The unstable substance i was treated with TMSI, producing the dimer ii as the sole product. (Matrix Presented) See: (a) Walker, G. N. J. Am. Chem. Soc. 1955, 77, 3844. (b) Burton, H.; Duffield, J. A.; Prail, P. F. G. J. Chem. Soc. 1950, 1062. (c) Beer, R. J. S.; Mcgrath, L.; Robertson, A.; Woodier, A. B. J. Chem. Soc. 1949, 2061. (d) Beer, R. J S.; Clarke, K.; Khorana, H. G.; Robertson, A. J. Chem. Soc. 1948, 2223. (e) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483. (f) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431. (g) Deibel, R. M. B.; Chedekel, M. R. J. Am. Chem. Soc. 1984, 106, 5884. (h) Heacock, R. A. Chem. Rev. 1959, 59, 181.
62. This difficulty was observed in a short synthesis of the known 6-acetoxy-7-methoxyindole (i). The unstable substance i was treated with TMSI, producing the dimer ii as the sole product. (Matrix Presented) See: (a) Walker, G. N. J. Am. Chem. Soc. 1955, 77, 3844. (b) Burton, H.; Duffield, J. A.; Prail, P. F. G. J. Chem. Soc. 1950, 1062. (c) Beer, R. J. S.; Mcgrath, L.; Robertson, A.; Woodier, A. B. J. Chem. Soc. 1949, 2061. (d) Beer, R. J S.; Clarke, K.; Khorana, H. G.; Robertson, A. J. Chem. Soc. 1948, 2223. (e) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483. (f) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431. (g) Deibel, R. M. B.; Chedekel, M. R. J. Am. Chem. Soc. 1984, 106, 5884. (h) Heacock, R. A. Chem. Rev. 1959, 59, 181.
63. This difficulty was observed in a short synthesis of the known 6-acetoxy-7-methoxyindole (i). The unstable substance i was treated with TMSI, producing the dimer ii as the sole product. (Matrix Presented) See: (a) Walker, G. N. J. Am. Chem. Soc. 1955, 77, 3844. (b) Burton, H.; Duffield, J. A.; Prail, P. F. G. J. Chem. Soc. 1950, 1062. (c) Beer, R. J. S.; Mcgrath, L.; Robertson, A.; Woodier, A. B. J. Chem. Soc. 1949, 2061. (d) Beer, R. J S.; Clarke, K.; Khorana, H. G.; Robertson, A. J. Chem. Soc. 1948, 2223. (e) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483. (f) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431. (g) Deibel, R. M. B.; Chedekel, M. R. J. Am. Chem. Soc. 1984, 106, 5884. (h) Heacock, R. A. Chem. Rev. 1959, 59, 181.
64. This difficulty was observed in a short synthesis of the known 6-acetoxy-7-methoxyindole (i). The unstable substance i was treated with TMSI, producing the dimer ii as the sole product. (Matrix Presented) See: (a) Walker, G. N. J. Am. Chem. Soc. 1955, 77, 3844. (b) Burton, H.; Duffield, J. A.; Prail, P. F. G. J. Chem. Soc. 1950, 1062. (c) Beer, R. J. S.; Mcgrath, L.; Robertson, A.; Woodier, A. B. J. Chem. Soc. 1949, 2061. (d) Beer, R. J S.; Clarke, K.; Khorana, H. G.; Robertson, A. J. Chem. Soc. 1948, 2223. (e) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483. (f) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431. (g) Deibel, R. M. B.; Chedekel, M. R. J. Am. Chem. Soc. 1984, 106, 5884. (h) Heacock, R. A. Chem. Rev. 1959, 59, 181.
65. This difficulty was observed in a short synthesis of the known 6-acetoxy-7-methoxyindole (i). The unstable substance i was treated with TMSI, producing the dimer ii as the sole product. (Matrix Presented) See: (a) Walker, G. N. J. Am. Chem. Soc. 1955, 77, 3844. (b) Burton, H.; Duffield, J. A.; Prail, P. F. G. J. Chem. Soc. 1950, 1062. (c) Beer, R. J. S.; Mcgrath, L.; Robertson, A.; Woodier, A. B. J. Chem. Soc. 1949, 2061. (d) Beer, R. J S.; Clarke, K.; Khorana, H. G.; Robertson, A. J. Chem. Soc. 1948, 2223. (e) Chan, A. C.; Hilliard, P. R., Jr. Tetrahedron Lett. 1989, 30, 6483. (f) d'Ischia, M.; Prota, G. Tetrahedron 1987, 43, 431. (g) Deibel, R. M. B.; Chedekel, M. R. J. Am. Chem. Soc. 1984, 106, 5884. (h) Heacock, R. A. Chem. Rev. 1959, 59, 181.
66. (a) Beer, R. J. S.; Clarke, K.; Davenport, H. F.; Robertson, A. J. Chem. Soc. 1951, 2029.
67. (b) Bennington, F.; Morin, R. D.; Clark, L. C., Jr. J. Org. Chem. 1959, 24, 917.
68. Kosuge, T.; Ishida, H.; Inabe, A.; Nukaya, H. Chem. Pharm. Bull. 1985, 33, 1414.
69. This material has interesting chemical and physical characteristics. The solvent must be removed immediately after the hydrogenolysis to prevent the white product from turning to a black sludge. This oxindole 31 would also change from a white color to a metallic gray simply by drying on the vacuum pump. These decomposition properties are no doubt due to the autoxidation of the indole tautomer form.
70. The undesired regioisomer was obtained in less than 1% yield, and the bis-alkylated material was produced in only 8.3% yield. This selectivity is presumably a manifestation of the domination of inductive effects of the amide functionality directing the alkylation to the 7-position.
71. The structure of compound 33 was confirmed by simply tosylating 33 and comparing the product (37) to the same substance prepared from 31. The two independently synthesized products were identical in every way. (Matrix Presented)
72. (a) Kishi, Y.; Nakatsuka, S.; Fukuyama, T.; Havel, M. J. Am. Chem. Soc. 1973, 95, 6494.
73. (b) Robinson, B. Chem. Rev. 1969, 69, 785.
74. Sirowej, H.; Khan, S. A.; Plieninger, H. Synthesis 1972, 84.
75. Williams, R. M.; Glinka, T. Tetrahedron Lett. 1986, 27, 3581.
76. Sakaitani, M.; Ohfune, Y. J. Am. Chem. Soc. 1990, 112, 1150.
77. Yoshimura, J.; Yamaura, M.; Suzuki, T.; Hashimoto, H. Chem. Lett. 1983, 1001.
78. N2′ fashion, furnishing the spiro lactones.
79. (a) Giovannini, A.; Savoia, D.; Umani-Ronchi, A. J. Org. Chem. 1989, 54, 228.
80. (b) Flynn, D. L.; Zelle, R. E.; Grieco, P. A. J. Org. Chem. 1983, 48, 2424.
81. 2 will also cleave lactam carbamates including BOC-protected lactams; see: Wei, Z.-Y.; Knaus, E. E.; Tetrahedron Lett. 1994, 35, 847.
82. 2 will also cleave lactam carbamates including BOC-protected lactams; see: Wei, Z.-Y.; Knaus, E. E.; Tetrahedron Lett. 1994, 35, 847.
83. Williams, R. M.; Brunner, E. J.; Sabol, M. R. Synthesis 1988, 963.
84. Corey, E. J.; Kim, C. U.; Takeda, M. Tetrahedron Lett. 1972, 13, 4339.
85. (a) Magid, R. M.; Fruchey, O. S.; Johnson, W. L.; Allen, T. G. J. Org. Chem. 1979, 44, 359.
86. (b) Magid, R. A. Tetrahedron 1980, 36, 1901.
87. N2′ reaction; see: (a) Denmark, S. A.; Henke, B. R. J. Am. Chem. Soc. 1991, 113, 2177. (b) Denmark, S. A.; Henke, B. R. J. Am. Chem. Soc. 1989, 111, 8022.
88. N2′ reaction; see: (a) Denmark, S. A.; Henke, B. R. J. Am. Chem. Soc. 1991, 113, 2177. (b) Denmark, S. A.; Henke, B. R. J. Am. Chem. Soc. 1989, 111, 8022.
89. (a) Hutchison, A. J.; Kishi, Y. J. Am. Chem. Soc. 1979, 101, 6786.
90. (b) Guller, R.; Borschberg, H.-J. Tetrahedron Lett 1994, 35, 865.
91. Trost, B. M.; Fortunak, J. M. D. Organometallics 1982, 1, 7.
92. (a) Ashimori, A.; Overman, L. E. J. Org. Chem. 1992, 57, 4571.
93. (b) Karabelas, K.; Westerlund, C.; Hallberg, A. J. Org. Chem. 1985, 50, 3896.
94. (c) Cava, M. P.; Kevinson, M. I. Tetrahedron 1985, 41, 5061 and literature cited therein.
95. In a recently reported synthesis of gelsemine, a tertian lactam was reduced in the presence of a secondary lactam with DIBAH. However, this reagent failed on substrates 69; see: Dutton, J. K.; Steel, R. W.; Tasker, A. S.; Popsavin, V.; Johnson, A. P. J. Chem. Soc., Chem. Commun. 1994, 765.
96. Martin, S. F.; Benage, B.; Geraci, L. S.; Hunter, J. E.; Mortimore, M. J. Am. Chem. Soc. 1991, 113, 6161.
97. (a) Yoon, N. M.; Brown, H. C. J. Am. Chem. Soc. 1968, 90, 2927.
98. (b) Marlett, E. M.; Park, W. S.; J. Org. Chem. 1990, 55, 2968.
99. (c) Jorgenson, M. J. Tetrahedron Lett. 1962, 559.
100. 3. Newcombe, N. J.; Fang, Y.; Vijn, R. J.; Hiemstra, H.; Speckamp, W. N. J. Chem. Soc., Chem. Commun. 1994, 767.
101. (a) Gaskell, A. J.; Radunz, H. -E.; Winterfeldt, E. Tetrahedron Lett. 1970, 5361.
102. (b) Winterfeldt, E.; Gaskell, A. J.; Korth, T.; Radnuz, H.-E.; Walkowiak, M. Chem. Ber. 1969, 102, 3558.
103. (c) Hollinshead, S. P.; Grubisha, D. S.; Bennett, D. W.; Cook, J. M. Heterocycles 1989, 29, 529.
104. 4-pyridine. See: (a) Takayama, H.; Kitajima, M.; Ogata, K.; Sakai, S. J. Org. Chem. 1992, 57, 4583. (b) Takayama, H.; Odaka, H.; Aimi, N.; Sakai, S. Tetrahedron Lett. 1990, 38, 5483. (c) Takayama, H.; Masubuchi, K.; Kitajima, M.; Aimi, N.; Sakai, S. Tetrahedron 1989, 45, 1327. (d) Fu, X.; Cook, J. M. J. Org. Chem. 1993, 58, 661
105. 4-pyridine. See: (a) Takayama, H.; Kitajima, M.; Ogata, K.; Sakai, S. J. Org. Chem. 1992, 57, 4583. (b) Takayama, H.; Odaka, H.; Aimi, N.; Sakai, S. Tetrahedron Lett. 1990, 38, 5483. (c) Takayama, H.; Masubuchi, K.; Kitajima, M.; Aimi, N.; Sakai, S. Tetrahedron 1989, 45, 1327. (d) Fu, X.; Cook, J. M. J. Org. Chem. 1993, 58, 661
106. 4-pyridine. See: (a) Takayama, H.; Kitajima, M.; Ogata, K.; Sakai, S. J. Org. Chem. 1992, 57, 4583. (b) Takayama, H.; Odaka, H.; Aimi, N.; Sakai, S. Tetrahedron Lett. 1990, 38, 5483. (c) Takayama, H.; Masubuchi, K.; Kitajima, M.; Aimi, N.; Sakai, S. Tetrahedron 1989, 45, 1327. (d) Fu, X.; Cook, J. M. J. Org. Chem. 1993, 58, 661
107. 4-pyridine. See: (a) Takayama, H.; Kitajima, M.; Ogata, K.; Sakai, S. J. Org. Chem. 1992, 57, 4583. (b) Takayama, H.; Odaka, H.; Aimi, N.; Sakai, S. Tetrahedron Lett. 1990, 38, 5483. (c) Takayama, H.; Masubuchi, K.; Kitajima, M.; Aimi, N.; Sakai, S. Tetrahedron 1989, 45, 1327. (d) Fu, X.; Cook, J. M. J. Org. Chem. 1993, 58, 661
108. (e) Takayama, H.; Tominaga, Y.; Kitajima, M.; Aimi, N.; Sakai, S. J. Org. Chem. 1994, 59, 4381.
109. Similar problems were observed during the total synthesis of isopteropodine and pteropodine; see: Martin, S. F.; Mortimore, M. Tetrahedron Lett. 1990, 31, 4557. In this system, the solution involved treating the chloroindolenines with silver perchlorate in methanolic perchloric acid. This method was attempted on substrate 73, but unfortunately it failed to produce any desired product.
110. Osamura, Y.; Nakamura, K. J. Am. Chem. Soc. 1993, 115, 9112.
111. Parker, A. J. Chem. Rev. 1969, 69, 1.
112. (a) Owellen, R. J.; Hartke, C. J. Org. Chem. 1976, 41, 102.
113. (b) Kuehne, M. E.; Roland, D. M.; Hafter, R. J. Org. Chem. 1978, 43, 3703.
114. (c) Awang, D. V. C.; Vincent, A.; Kidack, D. Can. J. Chem. 1984, 62, 2667.
115. (Matrix Presented)