Total synthesis of (±)-deethylibophyllidine: Studies of a Fischer indolization route and a successful approach via a Pummerer rearrangement/thionium ion-mediated indole cyclization

Journal of Organic Chemistry

Volumn 61, Issue 20, 1996, Pages 7106-7115

  Bonjoch, Josep ^a   Catena, Juanlo ^a   Valls, Nativitat ^a  

^a UNIVERSITY OF BARCELONA   (Spain)

Author keywords

[No Author keywords available]

Indexed keywords

ALKALOID; DEETHYLIBOPHYLLIDINE; INDOLE DERIVATIVE; UNCLASSIFIED DRUG;

ARTICLE; DRUG SYNTHESIS; NUCLEAR MAGNETIC RESONANCE; REACTION ANALYSIS;

EID: 0029822041     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo960848z     Document Type: Article

References (91)

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2. For leading references regarding isolation, characterization, and biosynthesis of ibophyllidine alkaloids, see: (a) Khuong-Huu, F.; Cesario, M.; Guilhem, J.; Goutarel, R. Tetrahedron 1976, 32, 2539. (b) Kan, C.; Husson, H.-P.; Jacquemin, H.; Kan, S.-K.; Lounasmaa, M. Tetrahedron Lett. 1980, 21, 55. (c) Kan, C.; Husson, H.-P.; Kan, S.-K.; Lounasmaa, M. Tetrahedron Lett. 1980, 21, 3363. (d) Kuehne, M. E.; Pitner, J. B. J. Org. Chem. 1989, 54, 4553. (e) Saxton, J. E. The Ibogamine-Catharanthine Group. In Monoterpenoid Indole Alkaloids, supplement to part 4, Saxton, J. E., Ed. in The Chemistry of Heterocyclic Compounds, Taylor, E. C., Ed.; John Wiley: Chichester, 1994; Vol. 25, pp 487-521.
3. For leading references regarding isolation, characterization, and biosynthesis of ibophyllidine alkaloids, see: (a) Khuong-Huu, F.; Cesario, M.; Guilhem, J.; Goutarel, R. Tetrahedron 1976, 32, 2539. (b) Kan, C.; Husson, H.-P.; Jacquemin, H.; Kan, S.-K.; Lounasmaa, M. Tetrahedron Lett. 1980, 21, 55. (c) Kan, C.; Husson, H.-P.; Kan, S.-K.; Lounasmaa, M. Tetrahedron Lett. 1980, 21, 3363. (d) Kuehne, M. E.; Pitner, J. B. J. Org. Chem. 1989, 54, 4553. (e) Saxton, J. E. The Ibogamine-Catharanthine Group. In Monoterpenoid Indole Alkaloids, supplement to part 4, Saxton, J. E., Ed. in The Chemistry of Heterocyclic Compounds, Taylor, E. C., Ed.; John Wiley: Chichester, 1994; Vol. 25, pp 487-521.
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5. For leading references regarding isolation, characterization, and biosynthesis of ibophyllidine alkaloids, see: (a) Khuong-Huu, F.; Cesario, M.; Guilhem, J.; Goutarel, R. Tetrahedron 1976, 32, 2539. (b) Kan, C.; Husson, H.-P.; Jacquemin, H.; Kan, S.-K.; Lounasmaa, M. Tetrahedron Lett. 1980, 21, 55. (c) Kan, C.; Husson, H.-P.; Kan, S.-K.; Lounasmaa, M. Tetrahedron Lett. 1980, 21, 3363. (d) Kuehne, M. E.; Pitner, J. B. J. Org. Chem. 1989, 54, 4553. (e) Saxton, J. E. The Ibogamine-Catharanthine Group. In Monoterpenoid Indole Alkaloids, supplement to part 4, Saxton, J. E., Ed. in The Chemistry of Heterocyclic Compounds, Taylor, E. C., Ed.; John Wiley: Chichester, 1994; Vol. 25, pp 487-521.
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16. (c) Recently, we have described another synthetic approach to this target: Fernàndez, J.-C.; Valls. N.; Bosch, J.; Bonjoch, J. J. Chem. Soc., Chem. Commun. 1985, 2317.
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19. For the only previously described synthetic strategy, see: Magnus, P. D.; Exon, C.; Sear, N. L. Tetrahedron 1983, 39, 3725.
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22. By Birch reduction of 4-methoxyphenethylamines: (a) Ueda, N.; Tokuyama, T.; Sakan, T. Bull. Chem. Soc. Jpn. 1966, 39, 2012. (b) Sawlewicz, P.; Smulkowski, M.; Sowinski, P.; Borowaki, E. Pol. J. Chem. 1978, 52, 219.
23. By Birch reduction of 4-methoxyphenethylamines: (a) Ueda, N.; Tokuyama, T.; Sakan, T. Bull. Chem. Soc. Jpn. 1966, 39, 2012. (b) Sawlewicz, P.; Smulkowski, M.; Sowinski, P.; Borowaki, E. Pol. J. Chem. 1978, 52, 219.
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26. For approaches leading to 1,2,3,3a,4,5-hexahydroindol-6-ones, see: (a) from 1,3-cyclohexanedione, Bryson, T. A.; Gammill, R. B. Tetrahedron Lett. 1974, 3963. (b) From 6-methoxyindoline, Iida, H.; Aoyagi, S.; Kibayashi J. Chem. Soc., Perkin Trans. 1 1975, 2502. Iida, H.; Yuasa, Y.; Kibayashi, C. Synthesis 1977, 879. From pyrrolidine-2-thiones, Michael, J. P.; Howard, A. S.; Katz, R. B.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4751. Michael, J. P.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4755. For the reduction to octahydroderivatives: Higashiyama, H.; Honda, T.; Otomasu, H.; Kametani, T. Planta Med. 1983, 48, 268. Ito, K.; Naruma, M.; Furukawa, H. J. Chem. Soc., Chem. Commun. 1975, 681.
27. For approaches leading to 1,2,3,3a,4,5-hexahydroindol-6-ones, see: (a) from 1,3-cyclohexanedione, Bryson, T. A.; Gammill, R. B. Tetrahedron Lett. 1974, 3963. (b) From 6-methoxyindoline, Iida, H.; Aoyagi, S.; Kibayashi J. Chem. Soc., Perkin Trans. 1 1975, 2502. Iida, H.; Yuasa, Y.; Kibayashi, C. Synthesis 1977, 879. From pyrrolidine-2-thiones, Michael, J. P.; Howard, A. S.; Katz, R. B.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4751. Michael, J. P.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4755. For the reduction to octahydroderivatives: Higashiyama, H.; Honda, T.; Otomasu, H.; Kametani, T. Planta Med. 1983, 48, 268. Ito, K.; Naruma, M.; Furukawa, H. J. Chem. Soc., Chem. Commun. 1975, 681.
28. For approaches leading to 1,2,3,3a,4,5-hexahydroindol-6-ones, see: (a) from 1,3-cyclohexanedione, Bryson, T. A.; Gammill, R. B. Tetrahedron Lett. 1974, 3963. (b) From 6-methoxyindoline, Iida, H.; Aoyagi, S.; Kibayashi J. Chem. Soc., Perkin Trans. 1 1975, 2502. Iida, H.; Yuasa, Y.; Kibayashi, C. Synthesis 1977, 879. From pyrrolidine-2-thiones, Michael, J. P.; Howard, A. S.; Katz, R. B.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4751. Michael, J. P.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4755. For the reduction to octahydroderivatives: Higashiyama, H.; Honda, T.; Otomasu, H.; Kametani, T. Planta Med. 1983, 48, 268. Ito, K.; Naruma, M.; Furukawa, H. J. Chem. Soc., Chem. Commun. 1975, 681.
29. For approaches leading to 1,2,3,3a,4,5-hexahydroindol-6-ones, see: (a) from 1,3-cyclohexanedione, Bryson, T. A.; Gammill, R. B. Tetrahedron Lett. 1974, 3963. (b) From 6-methoxyindoline, Iida, H.; Aoyagi, S.; Kibayashi J. Chem. Soc., Perkin Trans. 1 1975, 2502. Iida, H.; Yuasa, Y.; Kibayashi, C. Synthesis 1977, 879. From pyrrolidine-2-thiones, Michael, J. P.; Howard, A. S.; Katz, R. B.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4751. Michael, J. P.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4755. For the reduction to octahydroderivatives: Higashiyama, H.; Honda, T.; Otomasu, H.; Kametani, T. Planta Med. 1983, 48, 268. Ito, K.; Naruma, M.; Furukawa, H. J. Chem. Soc., Chem. Commun. 1975, 681.
30. For approaches leading to 1,2,3,3a,4,5-hexahydroindol-6-ones, see: (a) from 1,3-cyclohexanedione, Bryson, T. A.; Gammill, R. B. Tetrahedron Lett. 1974, 3963. (b) From 6-methoxyindoline, Iida, H.; Aoyagi, S.; Kibayashi J. Chem. Soc., Perkin Trans. 1 1975, 2502. Iida, H.; Yuasa, Y.; Kibayashi, C. Synthesis 1977, 879. From pyrrolidine-2-thiones, Michael, J. P.; Howard, A. S.; Katz, R. B.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4751. Michael, J. P.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4755. For the reduction to octahydroderivatives: Higashiyama, H.; Honda, T.; Otomasu, H.; Kametani, T. Planta Med. 1983, 48, 268. Ito, K.; Naruma, M.; Furukawa, H. J. Chem. Soc., Chem. Commun. 1975, 681.
31. For approaches leading to 1,2,3,3a,4,5-hexahydroindol-6-ones, see: (a) from 1,3-cyclohexanedione, Bryson, T. A.; Gammill, R. B. Tetrahedron Lett. 1974, 3963. (b) From 6-methoxyindoline, Iida, H.; Aoyagi, S.; Kibayashi J. Chem. Soc., Perkin Trans. 1 1975, 2502. Iida, H.; Yuasa, Y.; Kibayashi, C. Synthesis 1977, 879. From pyrrolidine-2-thiones, Michael, J. P.; Howard, A. S.; Katz, R. B.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4751. Michael, J. P.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4755. For the reduction to octahydroderivatives: Higashiyama, H.; Honda, T.; Otomasu, H.; Kametani, T. Planta Med. 1983, 48, 268. Ito, K.; Naruma, M.; Furukawa, H. J. Chem. Soc., Chem. Commun. 1975, 681.
32. For approaches leading to 1,2,3,3a,4,5-hexahydroindol-6-ones, see: (a) from 1,3-cyclohexanedione, Bryson, T. A.; Gammill, R. B. Tetrahedron Lett. 1974, 3963. (b) From 6-methoxyindoline, Iida, H.; Aoyagi, S.; Kibayashi J. Chem. Soc., Perkin Trans. 1 1975, 2502. Iida, H.; Yuasa, Y.; Kibayashi, C. Synthesis 1977, 879. From pyrrolidine-2-thiones, Michael, J. P.; Howard, A. S.; Katz, R. B.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4751. Michael, J. P.; Zwane, M. I. Tetrahedron Lett. 1992, 33, 4755. For the reduction to octahydroderivatives: Higashiyama, H.; Honda, T.; Otomasu, H.; Kametani, T. Planta Med. 1983, 48, 268. Ito, K.; Naruma, M.; Furukawa, H. J. Chem. Soc., Chem. Commun. 1975, 681.
33. All synthetic compounds are racemic. The schemes depict only the enantiomer bearing the natural configuration at C-14.
34. 10a For the synthesis of hexahydroindol-6-ones by hypervalent iodine oxidation of tyramine derivatives, see: (a) Kita, Y.; Tohma, H.; Kikuchi, K.; Inagaki, M.; Yakura, T. J. Org. Chem. 1991, 56, 435. (b) Goldstein, D. M.; Wipf, P. Tetrahedron Lett. 1996, 37, 739.
35. 10a For the synthesis of hexahydroindol-6-ones by hypervalent iodine oxidation of tyramine derivatives, see: (a) Kita, Y.; Tohma, H.; Kikuchi, K.; Inagaki, M.; Yakura, T. J. Org. Chem. 1991, 56, 435. (b) Goldstein, D. M.; Wipf, P. Tetrahedron Lett. 1996, 37, 739.
36. (a) Hook, J. M.; Mander, L. N. Nat. Prod. Rep. 1986, 35-85.
37. (b) Rabideau, P. W.; Marcinow, Z. Org. React. 1992, 42, 1-334.
38. For the synthesis of 1, using sodium as reducing agent, see: Clarke, C. B.; Pinder, A. R. J. Chem. Soc. 1968, 1967.
39. On the contrary, when the acylation was carried out in the Schotten-Baumann conditions, acylated but not cyclized compound 3 was isolated (see Experimental Section).
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41. (b) Meyers, A. I.; Berney, D. J. Org. Chem. 1989, 54, 4673.
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46. For indolization upon the methine carbon in the Aspidosperma series, see: (a) Stork. G.; Dolfini, J. E. J. Am. Chem. Soc. 1963, 85, 2872. (b) Ban, Y.; Sato, Y.; Inoue, I.; Nagai, M.; Oishi, T.; Terashima, M.; Yonemitsu, O.; Kanaoka, Y. Tetrahedron Lett. 1966, 2261. (c) Inoue, I.; Ban, Y. J. Chem. Soc (C) 1970, 602. (d) Klioze, S. S.; Darmory, F. P. J. Org. Chem. 1975, 40, 1588. (e) Lawton, G.; Saxton, J. E.; Smith, A. J. Tetrahedron 1977, 33, 1641. (f) Pearson, A. J.; Rees, D. C. J. Chem. Soc., Perkin Trans. 1 1982, 2467.
47. For indolization upon the methine carbon in the Aspidosperma series, see: (a) Stork. G.; Dolfini, J. E. J. Am. Chem. Soc. 1963, 85, 2872. (b) Ban, Y.; Sato, Y.; Inoue, I.; Nagai, M.; Oishi, T.; Terashima, M.; Yonemitsu, O.; Kanaoka, Y. Tetrahedron Lett. 1966, 2261. (c) Inoue, I.; Ban, Y. J. Chem. Soc (C) 1970, 602. (d) Klioze, S. S.; Darmory, F. P. J. Org. Chem. 1975, 40, 1588. (e) Lawton, G.; Saxton, J. E.; Smith, A. J. Tetrahedron 1977, 33, 1641. (f) Pearson, A. J.; Rees, D. C. J. Chem. Soc., Perkin Trans. 1 1982, 2467.
48. For indolization upon the methine carbon in the Aspidosperma series, see: (a) Stork. G.; Dolfini, J. E. J. Am. Chem. Soc. 1963, 85, 2872. (b) Ban, Y.; Sato, Y.; Inoue, I.; Nagai, M.; Oishi, T.; Terashima, M.; Yonemitsu, O.; Kanaoka, Y. Tetrahedron Lett. 1966, 2261. (c) Inoue, I.; Ban, Y. J. Chem. Soc (C) 1970, 602. (d) Klioze, S. S.; Darmory, F. P. J. Org. Chem. 1975, 40, 1588. (e) Lawton, G.; Saxton, J. E.; Smith, A. J. Tetrahedron 1977, 33, 1641. (f) Pearson, A. J.; Rees, D. C. J. Chem. Soc., Perkin Trans. 1 1982, 2467.
49. For indolization upon the methine carbon in the Aspidosperma series, see: (a) Stork. G.; Dolfini, J. E. J. Am. Chem. Soc. 1963, 85, 2872. (b) Ban, Y.; Sato, Y.; Inoue, I.; Nagai, M.; Oishi, T.; Terashima, M.; Yonemitsu, O.; Kanaoka, Y. Tetrahedron Lett. 1966, 2261. (c) Inoue, I.; Ban, Y. J. Chem. Soc (C) 1970, 602. (d) Klioze, S. S.; Darmory, F. P. J. Org. Chem. 1975, 40, 1588. (e) Lawton, G.; Saxton, J. E.; Smith, A. J. Tetrahedron 1977, 33, 1641. (f) Pearson, A. J.; Rees, D. C. J. Chem. Soc., Perkin Trans. 1 1982, 2467.
50. For indolization upon the methine carbon in the Aspidosperma series, see: (a) Stork. G.; Dolfini, J. E. J. Am. Chem. Soc. 1963, 85, 2872. (b) Ban, Y.; Sato, Y.; Inoue, I.; Nagai, M.; Oishi, T.; Terashima, M.; Yonemitsu, O.; Kanaoka, Y. Tetrahedron Lett. 1966, 2261. (c) Inoue, I.; Ban, Y. J. Chem. Soc (C) 1970, 602. (d) Klioze, S. S.; Darmory, F. P. J. Org. Chem. 1975, 40, 1588. (e) Lawton, G.; Saxton, J. E.; Smith, A. J. Tetrahedron 1977, 33, 1641. (f) Pearson, A. J.; Rees, D. C. J. Chem. Soc., Perkin Trans. 1 1982, 2467.
51. For indolization upon the methine carbon in the Aspidosperma series, see: (a) Stork. G.; Dolfini, J. E. J. Am. Chem. Soc. 1963, 85, 2872. (b) Ban, Y.; Sato, Y.; Inoue, I.; Nagai, M.; Oishi, T.; Terashima, M.; Yonemitsu, O.; Kanaoka, Y. Tetrahedron Lett. 1966, 2261. (c) Inoue, I.; Ban, Y. J. Chem. Soc (C) 1970, 602. (d) Klioze, S. S.; Darmory, F. P. J. Org. Chem. 1975, 40, 1588. (e) Lawton, G.; Saxton, J. E.; Smith, A. J. Tetrahedron 1977, 33, 1641. (f) Pearson, A. J.; Rees, D. C. J. Chem. Soc., Perkin Trans. 1 1982, 2467.
52. For the same regioselectivity in the Aspidosperma series, see: Akagi, M.; Oishi, T.; Ban, Y. Tetrahedron Lett. 1969, 2063.
53. Crabb, T. A.; Newton, R. F.; Jackson, D. Chem. Rev. 1971, 71, 109.
54. (a) For interesting mechanistic aspects on the Fischer indolization upon β-amino ketones in this field, see: Ban, Y.; Iijima, I. Tetrahedron Lett. 1969, 2523. See also ref 23e.
55. (b) For a discussion about the stereochemical factors influencing the regiochemical course of Fischer indole synthesis, see: Freter, K.; Fuchs, V.; Pitner, T. P. J. Org. Chem. 1983, 48, 4593.
56. For conformational analysis of the cis-octahydroindole, see: Mokotoff, M.; Hill, S. T. J. Heterocycl. Chem. 1988, 25, 65. For the conformational preference in 3a-aryloctahydroindol-6-ones (i.e. mesembrine), see: Jeffs, P. W.; Hawks, R. L.; Farrier, D. S. J. Am. Chem. Soc. 1969, 91, 3831. Sánchez, I. H.; Larraza, M.-I.; Flores, H. J.; Díaz, E. Heterocycles 1985, 23, 593.
57. For conformational analysis of the cis-octahydroindole, see: Mokotoff, M.; Hill, S. T. J. Heterocycl. Chem. 1988, 25, 65. For the conformational preference in 3a-aryloctahydroindol-6-ones (i.e. mesembrine), see: Jeffs, P. W.; Hawks, R. L.; Farrier, D. S. J. Am. Chem. Soc. 1969, 91, 3831. Sánchez, I. H.; Larraza, M.-I.; Flores, H. J.; Díaz, E. Heterocycles 1985, 23, 593.
58. For conformational analysis of the cis-octahydroindole, see: Mokotoff, M.; Hill, S. T. J. Heterocycl. Chem. 1988, 25, 65. For the conformational preference in 3a-aryloctahydroindol-6-ones (i.e. mesembrine), see: Jeffs, P. W.; Hawks, R. L.; Farrier, D. S. J. Am. Chem. Soc. 1969, 91, 3831. Sánchez, I. H.; Larraza, M.-I.; Flores, H. J.; Díaz, E. Heterocycles 1985, 23, 593.
59. N-Benzyliodoacetamide was prepared from benzylamine and chloroacetyl chloride and later treatment of the resulting chlorocetamide with sodium iodide in 2-butanone according to Dufour, M.; Gramain, J.-C.; Husson, H.-P.; Sinibaldi, M.-E.; Troin, Y. J. Org. Chem. 1990, 55, 5483.
60. Operating with AcOH/NaOAc or EtOH/HCl instead of AcOH neat, the ratio of indole 17 increases and is the major product in the indolization.
61. For studies on the regioselectivity in the Fischer indolization of β-amino ketones, see: Bonjoch, J.; Casamitjana, N.; Gràcia, J.; Úbeda, M.-C.; Bosch, J. Tetrahedron Lett. 1990, 31, 2449.
62. The influence of the A 1,3 strain (Johnson, F. Chem. Rev. 1968, 68, 375) caused by the amide linkage in this conformational change was suggested by a reviewer. Also the difference in regioselectivity in the Fischer indole synthesis of hydroindolones could be accounted for considering that it occurs through the enehydrazine that minimizes the A 1,3 strain.
63. 13C NMR, see Table 2.
64. For a successful formation of C-6/C-7 bond by this coupling-type in β-unsubstituted indoles, see: Bennasar, M.-L.; Zulaica, E.; Jiménez, J.-M.; Bosch, J. J. Org. Chem. 1993, 58, 7756.
65. 3, HMQC) 18.4 (C-4), 23.6 (C-5), 26.4 (C-3), 29.7 (C-11), 36.7 (C-3a), 46.4 (C-2), 54.8 (C-10c), 109.6 (C-7), 110.0 (C-10b), 119.0 (C-9), 122.7 (C-8), 124.3 (C-10a), 126.2 (C-10), 131.2 (C-5a), 135.2 (C-6a), 170.4 (C-12).
66. A similar result has been observed in the Strychnos series: Bosch, J.; Amat, M.; Sanfeliu, E.; Miranda, M.-A. Tetrahedron 1985, 41, 2557.
67. The Pummerer rearrangement has emerged as a versatile and effective method for the generation of cationic reactive intermediates from sulfoxide precursors. For recent reviews, see: (a) Grierson, D. S.; Husson, H.-P. In Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon: Oxford, 1991; Vol. 6, pp 909-947. (b) Kennedy, M.; McKervey, M. A. Ibid. Vol. 7, pp 193-216. (c) De Lucchi, O.; Miotti, U.; Modena, G. Org. React. 1991, 40, 157-405.
68. The Pummerer rearrangement has emerged as a versatile and effective method for the generation of cationic reactive intermediates from sulfoxide precursors. For recent reviews, see: (a) Grierson, D. S.; Husson, H.-P. In Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon: Oxford, 1991; Vol. 6, pp 909-947. (b) Kennedy, M.; McKervey, M. A. Ibid. Vol. 7, pp 193-216. (c) De Lucchi, O.; Miotti, U.; Modena, G. Org. React. 1991, 40, 157-405.
69. The Pummerer rearrangement has emerged as a versatile and effective method for the generation of cationic reactive intermediates from sulfoxide precursors. For recent reviews, see: (a) Grierson, D. S.; Husson, H.-P. In Comprehensive Organic Synthesis; Trost, B. M., Ed.; Pergamon: Oxford, 1991; Vol. 6, pp 909-947. (b) Kennedy, M.; McKervey, M. A. Ibid. Vol. 7, pp 193-216. (c) De Lucchi, O.; Miotti, U.; Modena, G. Org. React. 1991, 40, 157-405.
70. (a) Amat, M.; Alvarez, M.; Bonjoch, J.; Casamitjana, N.; Gràcia, J.; Lavilla, R.; Garcías, X.; Bosch, J. Tetrahedron Lett. 1990, 31, 3453.
71. (b) Amat, M.; Linares, A.; Bosch, J. J. Org. Chem. 1990, 55, 6299.
72. (c) Gràcia, J.; Casamitjana, N.; Bonjoch, J.; Bosch, J. J. Org. Chem. 1994, 59, 3939.
73. Illi, V. O. Synthesis 1979, 136.
74. Yoshida, K.; Nakajima, S.; Wakamatsu, T.; Ban, Y.; Shibasaki, M. Heterocycles 1988, 27, 1167.
75. 40c,d upon phenyl vinyl sulfoxide, see: (a) Abbott, D. J.; Colonna, S.; Stirling, C. J. M. J. Chem. Soc., Perkin Trans. 1 1976, 492. (b) Maignan, C.; Guessous, A.; Rouessac, F. Tetrahedron Lett. 1986, 27, 2603. (c) Lee, A. W. M.; Chan, W. H.; Chan, E. T. T. J. Chem. Soc., Perkin Trans. 1 1992, 309. (d) Craig, D.; Daniels, K.; MacKenzie, A. R. Tetrahedron 1992, 48, 7803.
76. 40c,d upon phenyl vinyl sulfoxide, see: (a) Abbott, D. J.; Colonna, S.; Stirling, C. J. M. J. Chem. Soc., Perkin Trans. 1 1976, 492. (b) Maignan, C.; Guessous, A.; Rouessac, F. Tetrahedron Lett. 1986, 27, 2603. (c) Lee, A. W. M.; Chan, W. H.; Chan, E. T. T. J. Chem. Soc., Perkin Trans. 1 1992, 309. (d) Craig, D.; Daniels, K.; MacKenzie, A. R. Tetrahedron 1992, 48, 7803.
77. 40c,d upon phenyl vinyl sulfoxide, see: (a) Abbott, D. J.; Colonna, S.; Stirling, C. J. M. J. Chem. Soc., Perkin Trans. 1 1976, 492. (b) Maignan, C.; Guessous, A.; Rouessac, F. Tetrahedron Lett. 1986, 27, 2603. (c) Lee, A. W. M.; Chan, W. H.; Chan, E. T. T. J. Chem. Soc., Perkin Trans. 1 1992, 309. (d) Craig, D.; Daniels, K.; MacKenzie, A. R. Tetrahedron 1992, 48, 7803.
78. 40c,d upon phenyl vinyl sulfoxide, see: (a) Abbott, D. J.; Colonna, S.; Stirling, C. J. M. J. Chem. Soc., Perkin Trans. 1 1976, 492. (b) Maignan, C.; Guessous, A.; Rouessac, F. Tetrahedron Lett. 1986, 27, 2603. (c) Lee, A. W. M.; Chan, W. H.; Chan, E. T. T. J. Chem. Soc., Perkin Trans. 1 1992, 309. (d) Craig, D.; Daniels, K.; MacKenzie, A. R. Tetrahedron 1992, 48, 7803.
79. Compound 30 was a diastereomeric mixture at sulfur, which could not be separated at this stage.
80. 42d
81. (b) Amat, M.; Bosch, J. J. Org. Chem. 1992, 57, 5792.
82. (c) Amat, M.; Hadida, S.; Sathyanarayana, S.; Bosch, J. Tetrahedron Lett. 1996, 37, 3071.
83. (d) Takano, S.; Iida, H.; Inomata, K.; Ogasawara, K. Heterocycles 1993, 35, 47.
84. Besselièvre, R.; Husson, H.-P. Tetrahedron 1981, 37, Suppl. No. 1, 241.
85. 7 bond in the synthesis of Aspidosperma alkaloids, but using either an exocyclic or an endocyclic amide as the substrate: Gallagher, T.; Magnus, P.; Huffman, J. C. J. Am. Chem. Soc. 1983, 105, 4750.
86. See also, Magnus, P.; Sear, N. L.; Kim, C. S.; Vicker, N. J. Org. Chem. 1992, 57, 70 and references cited therein.
87. (a) Wenkert, E.; Orito, K.; Simmons, D. P.; Kunesh, N.; Ardisson, J.; Poisson, J. Tetrahedron 1983, 39, 3719.
88. (b) Wenkert, E.; Porter, B.; Simmons, D. P. J. Org. Chem. 1984, 49, 3733.
89. Solé, D.; Bonjoch, J.; Bosch, J. J. Org. Chem. 1996, 61, 4194. See also ref 37b, 37c.
90. (a) Stork, G.; Danheiser, R. L. J. Org. Chem. 1973, 38, 1775.
91. (b) Kende, A. S.; Fludzinski, P. Org. Synth. 1986, 64, 68.