Principles and Applications of Asymmetric Synthesis
.pdf392 ASYMMETRIC CATALYTIC HYDROGENATION AND OTHER REDUCTION REACTIONS
Lett. 1980, 729. (e) Miyano, S.; Nawa, M.; Mori, A.; Hashimoto, H. Bull. Chem. Soc. Jpn. 1984, 57, 2171.
43.Zhang, F.; Pai, C.; Chan, A. S. C. J. Am. Chem. Soc. 1998, 120, 5808.
44.Reetz, M. T.; Neugebauer, T. Angew. Chem. Int. Ed. Engl. 1999, 38, 179.
45.Kitamura, M.; Tokunaga, M.; Noyori, R. J. Org. Chem. 1992, 57, 4053.
46.Takaya, H.; Ohta, T.; Sayo, N.; Kumobayashi, H.; Akutagawa, S.; Inoue, S.; Kasahara, I.; Noyori, R. J. Am. Chem. Soc. 1987, 109, 1596.
47.Noyori, R.; Ohta, M.; Hsiao, Y.; Kitamura, M.; Ohta, T.; Takaya, H. J. Am. Chem. Soc. 1986, 108, 7117.
48.(a) Chan, A. S. C.; Pai, C. C. US Patent 5 886 182, 1999. (b) Benincori, T.; Brenna, E.; Sannicolo, F.; Trimarco, L.; Antognazza, P.; Cesarotti, E. J. Chem. Soc. Chem. Commun. 1995, 685. (c) Chem. Eng. News 1995, 73 (41), 72.
49.(a) Tani, K.; Yamagata, T.; Otsuka, S.; Akutagawa, S.; Kumobayashi, H.; Taketomi, T.; Takaya, H.; Miyashita, A.; Noyori, R. J. Chem. Soc. Chem. Commun. 1982, 600. (b) Tani, K.; Yamagata, T.; Akutagawa, S.; Kumobayashi, H.; Taketomi, T.; Takaya, H.; Miyashita, A.; Noyori, R.; Otsuka, S. J. Am. Chem. Soc. 1984, 106, 5208. (c) Frauenrath, H.; Philipps, T. Angew. Chem. Int. Ed. Engl. 1986, 25, 274.
50.Noyori, R. Asymmetric Catalysis in Organic Synthesis, John Wiley & Sons, Inc., New York, 1994, Chap. 3, p 96.
51.(a) Midland, M. M. Chem. Rev. 1989, 89, 1553. (b) Srebnik, M. Aldrichimica Acta.
1987, 20, 9.
52.Bothner-By, A. A. J. Am. Chem. Soc. 1951, 73, 846.
53.(a) Noyori, R. Pure Appl. Chem. 1981, 53, 2315. (b) Noyori, R. Tetrahedron 1994, 50, 4259.
54.(a) Noyori, R. CHEMTECH 1992, 22, 360. (b) Noyori, R.; Ikeda, T.; Ohkuma, T.; Widhalm, M.; Kitamura, M.; Takaya, H.; Akutagawa, S.; Sayo, N.; Saito, T.; Taketomi, T.; Kumobayashi, H. J. Am. Chem. Soc. 1989, 111, 9134.
55.Kitamura, M.; Ohkuma, T.; Inoue, S.; Sayo, N.; Kumobayashi, H.; Akutagawa, S.; Ohta, T.; Takaya, H.; Noyori, R. J. Am. Chem. Soc. 1988, 110, 629.
56.Nishi, T.; Kitamura, M.; Ohkuma, T.; Noyori, R. Tetrahedron Lett. 1988, 29, 6327.
57.Fryzuk, M. D.; Bosnich, B. J. Am. Chem. Soc. 1977, 99, 6262.
58.MacNeil, P. A.; Roberts, N. K.; Bosnich, B. J. Am. Chem. Soc. 1981, 103, 2273.
59.Burk, M. J.; Feaster, J. E.; Harlow, R. L. Organometallics 1990, 9, 2653.
60.Kawano, H.; Ishii, Y.; Saburi, M.; Uchida, Y. J. Chem. Soc. Chem. Commun.
1988, 87.
61.Chong, J. M.; Clarke, I. S.; Koch, I.; Olbach, P. C.; Taylor, N. J. Tetrahedron Asymmetry 1995, 6, 409.
62.Kuwano, R.; Sawamura, M.; Shirai, J.; Takahashi, M.; Ito, Y. Tetrahedron Lett. 1995, 36, 5239.
63.Short, R. P.; Kennedy, R. M.; Masamune, S. J. Org. Chem. 1989, 54, 1755.
64.Fan, Q.; Yeung, C. H.; Chan, A. S. C. Tetrahedron Asymmetry 1997, 8, 4041.
65.Mashima, K.; Hino, T.; Takaya, H. J. Chem. Soc. Dalton Trans. 1992, 2099.
6.7 REFERENCES 393
66.Noyori, R.; Ohkuma, T.; Kitamura, M.; Takaya, H.; Sayo, N.; Kumobayashi, H.; Akutagawa, S. J. Am. Chem. Soc. 1987, 109, 5856.
67.(a) Bennet, M. A.; Matheson, T. W. ``Catalysis by Ruthenium Compounds'' in Wilkinson, G.; Stone, F. G. A.; Abel, E. W. ed. Comprehensive Organometallic Chemistry, vol. 4, Chap. 32.9, Pergamon Press, Oxford, 1982. (b) Jardine, F. Prog. Inorg. Chem. 1984, 31, 265. (c) Noyori, R. Asymmetric Catalysis in Organic Synthesis, John Wiley & Sons, Inc., New York, 1994, p 65.
68.(a) Masamune, S.; Kennedy, R. M.; Peterson, J. S. J. Am. Chem. Soc. 1986, 108, 7404. (b) Brown, H. C.; Ramachandran, R. V. Acc. Chem. Res. 1992, 25, 16.
69.Ohkuma, T.; Ooka, H.; Hashiguchi, S.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1995, 117, 2675.
70.Kitamura, M.; Tokunaga, M.; Ohkuma, T.; Noyori, R. Org. Syn. 1993, 71, 1.
71.Doucet, H.; Ohkuma, T.; Murata, K.; Yokozawa, T.; Kozawa, M.; Katayama, E.; England, A. F.; Ikariya, T.; Noyori, R. Angew. Chem. Int. Ed. Engl. 1998, 37, 1703.
72.For review, see Herrmann, W. A.; Cornils, B. Angew. Chem. Int. Ed. Engl. 1997, 36, 1048.
73.Ohkuma, T.; Koizumi, M.; Doucet, H.; Pham, T.; Kozawa, M.; Murata, K.; Katayama, E.; Yokozawa, T.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1998, 120, 13529.
74.Marinetti, A.; GeneÃt, J.; Jus, S.; Blanc, D.; Ratovelomanana-Vidal, V. Chem. Eur.
J.1999, 5, 1160.
75.Fiaud, J. C.; Kagan, H. B. Bull. Soc. Chim. Fr. 1969, 2742.
76.(a) Hirao, A.; Itsuno, S.; Nakahama, S.; Yamazaki, N. J. Chem. Soc. Chem. Commun. 1981, 315. (b) Itsuno, S.; Hirao, A.; Nakahama, S.; Yamazaki, N.
J.Chem. Soc. Perkin Trans. 1 1983, 1673.
77.For a review, see Wallbaum, S.; Martens, J. Tetrahedron Asymmetry 1992, 3, 1475.
78.Corey, E. J.; Link, J. O. Tetrahedron Lett. 1989, 30, 6275.
79.Cai, D.; Tschaen, D.; Shi, Y.; Verhoeven, T. R.; Reamer, R. A.; Douglas, A. W.
Tetrahedron Lett. 1993, 34, 3243.
80.Corey, E. J.; Bakshi, R. K.; Shibata, S. J. Am. Chem. Soc. 1987, 109, 5551.
81.(a) Corey, E. J.; Shibata, S.; Bakshi, R. K. J. Org. Chem. 1988, 53, 2861. (b) Corey,
E.J.; Bakshi, R. K.; Shibata, S.; Chen, C.; Singh, V. K. J. Am. Chem. Soc. 1987, 109, 7925.
82.Corey, E. J.; Bakshi, R. K. Tetrahedron Lett. 1990, 31, 611.
83.Rama Rao, A. V.; Gurjar, M. K.; Sharma, P. A.; Kaiwar, V. Tetrahedron Lett. 1990, 31, 2341.
84.(a) Behnan, W.; Dauelsbery, Ch.; Wallbaum, S.; Martens, J.; Synth. Commun. 1992, 22, 2143. (b) Rama Rao, A. V.; Gurjar, M. K.; Kaiwar, V. Tetrahedron Asymmetry 1992, 3, 859.
85.(a) Youn, I. K.; Lee, S.; Pak, C. S. Tetrahedron Lett. 1988, 29, 4453. (b) Martens, J.; Dauelsberg, Ch.; Behnen, W.; Wallbaum, S. Tetrahedron Asymmetry 1992, 3, 347.
86.Corey, E. J.; Chen, C.; Reichard, G. A. Tetrahedron Lett. 1989, 30, 5547.
394ASYMMETRIC CATALYTIC HYDROGENATION AND OTHER REDUCTION REACTIONS
87.For studies of these reactions, see (a) Corey, E. J.; Link, J. O. Tetrahedron Lett. 1992, 33, 4141. (b) Nevalainen, V. Tetrahedron Asymmetry 1991, 2, 1133. (c) Corey, E. J.; Link, J. O.; Sarshar, S.; Shao, Y. Tetrahedron Lett. 1992, 33, 7103. (d) Corey, E. J.; Link, J. O.; Bakshi, R. K.; Shao, Y. Tetrahedron Lett. 1992, 33, 7071.
(e) Jones, D. K.; Liotta, D. C. J. Org. Chem. 1993, 58, 799.
88.Corey, E. J.; Reichard, G. A. Tetrahedron. Lett. 1989, 30, 5207.
89.(a) Corey, E. J. Chem. Soc. Rev. 1988, 17, 111. (b) Corey, E. J.; Gavai, A. V.
Tetrahedron Lett. 1988, 29, 3201.
90.Corey, E. J.; Jardine, P. D. S.; Mohri, T. Tetrahedron Lett. 1988, 29, 6409.
91.Corey, E. J.; Chen, C.; Parry, M. J. Tetrahedron Lett. 1988, 29, 2899.
92.Masui, M.; Shirori, T. Synlett 1996, 49.
93.Mehler, T.; Martens, J. Tetrahedron Asymmetry 1993, 4, 2299.
94.Willems, J. G. H.; Dommerholt, F. J.; Hammink, J. B.; Vaarhorst, A. M.; Thijs, L.; Zwanenburg, B. Tetrahedron Lett. 1995, 36, 603.
95.Wang, Z.; La, B.; Fortunak, J. M.; Meng, X. J.; Kabalka, G. W. Tetrahedron Lett. 1998, 39, 5501.
96.Singh, V. K. Synthesis 1992, 605.
97.For a review regarding the chiral oxazoborolidine±catalyzed reduction of carbonyl compounds, see Corey, E. J.; Helal, C. J. Angew. Chem. Int. Ed. Engl. 1998, 37, 1986.
98.For literature on the asymmetric hydrogenation of imines, see (a) Bakos, J.; ToÂth, I.; Heil, B.; MarkoÂ, L. J. Organomet. Chem. 1985, 279, 23. (b) Becalski, A. G.;
Cullen, W. R.; Fryzuk, M. D.; James, B. R.; Kang, G.; Rettig, S. J. Inorg. Chem.
Â
1991, 30, 5002. (c) Bakos, J.; Orosz, A.; Heil, B.; Laghmari, M.; Lhoste, P.; Sinou, D. J. Chem. Soc. Chem. Commun. 1991, 1684. (d) Chan, Y.; Ng, C.; Osborn, J. A. J. Am. Chem. Soc. 1990, 112, 9400. (e) Morimoto, T.; Achiwa, K. Tetrahedron Asymmetry 1995, 6, 2661. (f ) Tani, K.; Onouchi, J.; Yamagata, T.; Kataoka, Y. Chem. Lett. 1995, 955. (g) Chan, A. S. C.; Chen, C. C.; Lin, C. W.; Lin, Y. C.; Cheng, M. C.; Peng, S. M. J. Chem. Soc. Chem. Commun. 1995, 1767.
99.Oppolzer, W.; Wills, M.; Starkemann, C.; Bernardinelli, G.; Tetrahedron Lett. 1990, 31, 4117.
100.(a) Willoughby, C. A.; Buchwald, S. L. J. Am. Chem. Soc. 1992, 114, 7562.
(b)Willoughby, C. A.; Buchwald, S. L. J. Am. Chem. Soc. 1994, 116, 8952.
(c)Willoughby, C. A.; Buchwald, S. L. J. Am. Chem. Soc. 1994, 116, 11703.
(d)Bolm, C. Angew. Chem. Int. Ed. Engl. 1993, 32, 232.
101.For asymmetric hydrogenation, see (a) Burk, M. J.; Feaster, J. E. J. Am. Chem. Soc. 1992, 114, 6266. (b) Buriak, J. M.; Osborn, J. A. Organometallics 1996, 15, 3161. For asymmetric hydrosilylation, see (c) Tillack, A.; Lefeber, C.; Peulecke, N.; Thomas, D.; Rosenthal, U. Tetrahedron Lett. 1997, 38, 1533. (d) Becker, R.; Brunner, H.; Mahboobi, S.; Wiegrebe, W.; Angew. Chem. Int. Ed. Engl. 1985, 24, 995.
102.(a) Kagan, H. B. Pure Appl. Chem. 1975, 43, 401. (b) Levi, A.; Modena, G.; Scorrano, G. J. Chem. Soc. Chem. Commun. 1975, 6.
103.Verdaguer, X.; Lange, U. E. W.; Reding, M. T.; Buchwald, S. L. J. Am. Chem. Soc. 1996, 118, 6784.
104.Chin, B.; Buchwald, S. L. J. Org. Chem. 1996, 61, 5650.
6.7 REFERENCES 395
105.Verdaguer, X.; Lange, U. E. W.; Buchwald, S. L. Angew. Chem. Int. Ed. Engl. 1998, 37, 1103.
106.Evans, D. A., Nelson, S. G.; Gagne, M. R.; Muci, A. R. J. Am. Chem. Soc. 1993, 115, 9800.
107.Chowdhury, R. L.; BaÈckvall, J. J. Chem. Soc. Chem. Commun. 1991, 1063.
108.(a) Zassinovich, G.; Mestroni, G.; Gladiali, S. Chem. Rev. 1992, 92, 1051. (b) Gladiali, S.; Pinna, L.; Delogu, G.; DeMartin, S.; Zassinovich, G.; Mestroni, G. Tetrahedron Asymmetry 1990, 1, 635. (c) MuÈller, D.; Umbricht, G.; Weber, B.; Pfaltz, A. Helv. Chim. Acta 1991, 74, 232. (d) Krasik, P.; Alper, H. Tetrahedron 1994, 50, 4347. (e) Yang, H.; Alvarez, M.; Lugan, N.; Mathieu, R. J. Chem. Soc. Chem. Commun. 1995, 1721. (f ) Langer, T.; Helmchen, G. Tetrahedron Lett. 1996, 37, 1381. (g) Langer, T.; Janssen, J.; Helmchen, G. Tetrahedron Asymmetry 1996, 7, 1599. (h) Jiang, Y.; Jiang, Q.; Zhu, G.; Zhang, X. Tetrahedron Lett. 1997, 38, 215.
109.(a) Ishihara, K.; Mori, A.; Arai, I.; Yamamoto, H. Tetrahedron Lett. 1986, 27, 983.
(b)Mukaiyama, T.; Suzuki, K.; Soai, K.; Sato, T. Chem. Lett. 1979, 447. (c) Mukaiyama, T.; Suzuki, K. Chem. Lett. 1980, 255. (d) Tombo, G. M. R.; Didier, E.; Loubinoux, B. Synlett 1990, 547. (e) Niwa, S.; Soai, K. J. Chem. Soc. Perkin Trans. 1 1990, 937. (f ) Corey, E. J.; Cimprich, K. A. J. Am. Chem. Soc. 1994, 116, 3151.
110.(a) Matsumura, K.; Hashiguchi, S.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1997, 119, 8738. (b) Haack, K.; Hashiguchi, S.; Fuji, A.; Ikariya, T.; Noyori, R.
Angew. Chem. Int. Ed. Eng. 1997, 36, 285.
111.Uematsu, N.; Fujii, A.; Hashiguchi, S.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1996, 118, 4916.
112.Sammakia, T.; Stangeland, E. L. J. Org. Chem. 1997, 62, 6104.
113.Jiang, Y.; Jiang, Q.; Zhang, X. J. Am. Chem. Soc. 1998, 120, 3817.
114.See, for example, (a) Hashiguchi, S.; Fujii, A.; Takehara, J.; Ikariya, T.; Noyori, R. J. Am. Chem. Soc. 1995, 117, 7562. (b) Jiang, Q.; Van Plew, D.; Mutuza, S.; Zhang, X. Tetrahedron Lett. 1996, 37, 797. (c) Jiang, Y.; Jiang, Q.; Zhu, G.; Zhang, X. Tetrahedron Lett. 1997, 38, 215.
115.Takehara, J.; Hashiguchi, S.; Fujii, A.; Inoue, S.; Ikariya, T.; Noyori, R. J. Chem. Soc. Chem. Commun. 1996, 233.
116.Alonso, D. A.; Guijarro, D.; Pinho, P.; Temme, O.; Andersson, P. G. J. Org. Chem. 1998, 63, 2749.
117.(a) Roucoux, A.; Devocelle, M.; Carpentier, J.; Agbossou, F.; Mortreux, A. Synlett 1995, 358. (b) Zhang, X.; Taketomi, T.; Yoshizumi, T.; Kumobayashi, H.; Akutagawa, S.; Mashima, K.; Takaya, H. J. Am. Chem. Soc. 1993, 115, 3318.
(c)Mashima, K.; Akutagawa, T.; Zhang, X.; Takaya, H.; Taketomi, T.; Kumobayashi, H.; Akutagawa, S. J. Organomet. Chem. 1992, 428, 213. (d) Zhang, X.; Kumobayashi, H.; Takaya, H. Tetrahedron Asymmetry 1994, 5, 1179. (e) Everaere, K.; Carpentier, J.; Mortreux, A.; Bulliard, M. Tetrahedron Asymmetry 1998, 9, 2971. (f ) de Bellefon, C.; Tanchoux, N. Tetrahedron Asymmetry 1998, 9, 3677.
(g)Bernard, M.; Guiral, V.; Delbecq, F.; Fache, F.; Sautet, P.; Lemaire, M. J. Am. Chem. Soc. 1998, 120, 1441. (h) Murata, K.; Ikariya, T.; Noyori, R. J. Org. Chem. 1999, 64, 2186.
396 ASYMMETRIC CATALYTIC HYDROGENATION AND OTHER REDUCTION REACTIONS
118.Evans, D.; Osborn, J. A.; Wilkinson, G. J. Chem. Soc. A 1968, 3133.
119.(a) Casey, C. P.; Whiteker, G. T.; Melville, M. G.; Petrovich, L. M.; Gavney, J. A.; Powell, D. R. J. Am. Chem. Soc. 1992, 114, 5535. (b) Casey, C. P.; Petrovich, L. M. J. Am. Chem. Soc. 1995, 117, 6007.
120. (a) Agbossou, F.; Carpentier, J.; Mortreux, A. Chem. Rev. 1995, 95, 2485.
(b)Gladiali, S.; BayoÂn, J. C.; Claver, C. Tetrahedron Asymmetry 1995, 6, 1453.
121.Stille, J. K.; Su, H.; Brechot, P.; Parrinello, G.; Hegedus, L. S. Organometallics 1991, 10, 1183.
122.Discussions of Rh(I)±chiral phosphine complexes: (a) Hobbs, C. F.; Knowles, W.
S.J. Org. Chem. 1981, 46, 4422. (b) Gladiali, S.; Pinna, L. Tetrahedron Asymmetry
1990, 1, 693. (c) Gladiali, S.; Pinna, L. Tetrahedron Asymmetry 1991, 2, 623. (d) Becker, Y.; Eisenstadt, A.; Stille, J. K. J. Org. Chem. 1980, 45, 2145. (e) Delogu, G.; Faedda, G.; Gladiali, S. J. Organomet. Chem. 1984, 268, 167. (f ) Lee, C. W.; Alper, H. J. Org. Chem. 1995, 60, 499. (g) Stanley, G. In Scaros, M. G., Prunier,
M.L., eds. Catalysis of Organic Reactions, Marcel Dekker, Inc., New York, 1995, p 363.
123.Discussions of Rh(I)±achiral phosphite complexes: (a) van Leeuwen, P. W. N. M.; Roobeek, C. F. (Shell). Eur. Pat. Appl. 54986, 1982. (b) van Leeuwen, P. W. N. M.; Roobeek, C. F. J. Organomet. Chem. 1983, 258, 343. (c) Billig, E.; Abatjoglou,
A.G.; Bryant, D. R. (Union Carbide). U. S. Patent 4769498, 1988. (d) Cuny, G. D.; Buchwald, S. L. J. Am. Chem. Soc. 1993, 115, 2066. (e) van Rooy, A.; Orij, E. N.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. Organometallics 1995, 14, 34.
124.Discussions of Rh(I)±chiral phosphite complexes: (a) Wink, D. J.; Kwok, T. J.; Yee, A. Inorg. Chem. 1990, 29, 5006. (b) Kwok, J.; Wink, D. J. Organometallics 1993, 12, 1954. (c) Sakai, N.; Nozaki, K.; Mashima, K.; Takaya, H. Tetrahedron Asymmetry 1992, 3, 583. (d) Buisman, G. J. H.; Kamer, P. C. J.; van Leeuwen,
P.W. N. M. Tetrahedron Asymmetry 1993, 4, 1625. (e) Babin, J. E.; Whiteker,
G.T. WO 93/03839, U. S. Patent 911518, 1992; Chem. Abstr. 1993, 119, 159872h. (f ) Buisman, G. J. H.; Martin, M. E.; Vos, E. J.; Klootwijk, A.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. Tetrahedron Asymmetry 1995, 6, 719. (g) Buisman, G.
J.H.; Vos, E. J.; Kamer, P. C. J.; van Leeuwen, P. W. N. M. J. Chem. Soc. Dalton Trans. 1995, 409.
125.(a) Moser, W. R.; Papile, C. J.; Brannon, D. A.; Duwell, R. A.; Weininger, S. J.
J.Mol. Catal. 1987, 41, 271. (b) Unruh, J. D.; Christenson, J. R. J. Mol. Catal. 1982, 14, 19.
126.Rossi, A. R.; Ho¨mann, R. Inorg. Chem. 1975, 14, 365.
127.Casey, C. P.; Whiteker, G. T. Isr. J. Chem. 1990, 30, 299.
128.van der Veen, L. A.; Boele, M. D. K.; Bregman, F. R.; Kamer, P. C. J.; van Leeuwen, P. W. N. M.; Goubitz, K.; Fraanje, J.; Schenk, H.; Bo, C. J. Am. Chem. Soc. 1998, 120, 11616.
129.Nozaki, K.; Sakai, N.; Nanno, T.; Higashijima, T.; Mano, S.; Horiuchi, T.; Takaya, H. J. Am. Chem. Soc. 1997, 119, 4413.
Principles and Applications of Asymmetric Synthesis
Guo-Qiang Lin, Yue-Ming Li, Albert S.C. Chan
Copyright ( 2001 John Wiley & Sons, Inc.
ISBNs: 0-471-40027-0 (Hardback); 0-471-22042-6 (Electronic)
CHAPTER 7
Applications of Asymmetric Reactions
in the Synthesis of Natural Products
Chapter 2 to 6 have introduced a variety of reactions such as asymmetric C±C bond formations (Chapters 2, 3, and 5), asymmetric oxidation reactions (Chapter 4), and asymmetric reduction reactions (Chapter 6). Such asymmetric reactions have been applied in several industrial processes, such as the asymmetric synthesis of l-DOPA, a drug for the treatment of Parkinson's disease, via Rh(DIPAMP)-catalyzed hydrogenation (Monsanto); the asymmetric synthesis of the cyclopropane component of cilastatin using a copper complex± catalyzed asymmetric cyclopropanation reaction (Sumitomo); and the industrial synthesis of menthol and citronellal through asymmetric isomerization of enamines and asymmetric hydrogenation reactions (Takasago). Now, the side chain of taxol can also be synthesized by several asymmetric approaches.
This chapter presents some examples of the asymmetric synthesis of complicated natural products. These examples will demonstrate that building up these molecules is unlikely if we do not use the asymmetric synthesis methodology. Excellent accounts by Masamune et al.1 and Noyori2 give a clear picture of the strategies for stereochemical control in organic synthesis.
Finally, this chapter discusses the synthesis of two taxol components: baccatin III, the polycyclic part of taxol; and the side chain of taxol. Although several groups have completed the total synthesis of taxol, work on taxol synthesis is still far from over. Chemists working in the area of asymmetric synthesis will ®nd challenge and opportunity in Section 7.5 of this chapter.
7.1THE SYNTHESIS OF ERYTHRONOLIDE A
Facing the challenge of synthesizing the antibiotic erythromycin A 1a, Woodward's group took advantage of a cyclic system to achieve diastereofacial selectivity, the so-called cyclic approach.3 This approach was taken to deal with the common problem of low diastereoselectivity associated with acyclic substances.
The aglycone part of erythromycin A (1b) can be considered as pseudosymmetric (i.e., the stereochemistry of fragment C-4 to C-6 and that of C-10 to C-12 can be regarded as the same). Retro synthetic analysis suggests that the
397
398 APPLICATIONS OF ASYMMETRIC REACTIONS
Scheme 7±1. Retro synthetic analysis of the aglycone of erythromycin A (1a).
common intermediate 4 could be the ideal starting material for the construction of the two segments A (2) and B (3). With this approach, most of the stereochemistry in 1b will then be built on a rigid dithiadecalin ring system, and the sulfur atoms are removed at the ®nal stage (Scheme 7±1).
Woodward's achievement in constructing the 10 chiral centers of 1b relied on the cyclic ``substrate control'' approach. Erythromycin A (1a) was ®nally synthesized by combining compound 1b with a long chain residue. Although this achievement represented a historic milestone at that time, it also attested to the limitations of this popular traditional approach.
Synthesis of the common intermediate C (4), and its further conversion to 2 and 3 is illustrated in Scheme 7±3. Two racemic compounds, …G†-7 and …G†- 10, are prepared from readily available starting materials 5 and 8, respectively (Scheme 7±2). Coupling of 7 and 10 gives a mixture of diastereomers 11. An intramolecular aldol reaction of 11 catalyzed by d-proline yields diastereomers 12 and 13 in equal molar ratios (about 36% ee for each diastereomer). Compound 12, the desired ketone, is converted to 14, which is further puri®ed by crystallization to give the compound in the desired stereochemistry in sterically pure form. Reduction of the ketone carbonyl group and subsequent methoxy
7.1 THE SYNTHESIS OF ERYTHRONOLIDE A |
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Scheme 7±2
Scheme 7±3. Synthesis of intermediate C.
methyl (MOM) protection furnishes compound 15. Osmium tetroxide oxidation and acetonide protection complete the synthesis of compound 4 (intermediate C) and thus accomplish the ®rst round of the synthesis (Scheme 7±3).
All the new chiral centers are controlled by the rigid structure of the dithiadecalin system. Taking the NaBH4 reduction of 14 as an example, the orientation of the fused rings forces the Hÿ to attack from the Si-prochiral face of the carbonyl group (Fig. 7±1).
Thus, acid cleavage of the protective groups MOM and acetonide in 4 provides compound 3 (fragment B); desulfuration and oxidation of the hydroxyl group give compound 2 (fragment A) (Scheme 7±4).
The next step to erythronolide A is the coupling of fragments A and B. Asymmetric aldol reaction of aldehyde 2 with a lithium enolate generated from
400 APPLICATIONS OF ASYMMETRIC REACTIONS
Figure 7±1. Transition state of compound 14 in NaBH4 reduction.
Scheme 7±4
3 followed by oxidation of the resulting hydroxy group gives the expected compound 16. This compound can be further converted to compound 17 via C-9 enolization. The following several steps are the chemistry at C-8 and C-7. Compound 17 is subjected to NaBH4 reduction and mesylation, a¨ording compound 18, in which the C±7 carbonyl group is converted to CH-OMs. Elimination of the mesyl group converts compound 18 to a,b-unsaturated compound 19, and subsequent phenyl methanethiolate addition provides compound 20. From compound 20 to aldehyde 22 is well established procedure (Scheme 7±5).
Having built up the desired stereochemistry at C-5 to C-13 as shown in compound 22, the next step is the connection of the C-1 to C-3 fragment. An aldol reaction of 22 with lithium enolate provides 23 with the desired C-2 stereochemistry.
Finally, macrocyclization is carried out via protection and deprotection sequences and cyclization of the activated ester 26, and this accomplishes the synthesis of 27 (Scheme 7±6), which, through deprotection and glycosidation, can be converted to erythromycin A, a compound containing a ``hopelessly complex'' array of chiral centers.4
7.2THE SYNTHESIS OF 6-DEOXYERYTHRONOLIDE
Considering the entire synthesis illustrated in the previous section, clearly the construction of such a complicated molecule with all the desired stereogenic centers is highly tedious and demanding work. Therefore, an entirely di¨erent conceptual method based on double asymmetric induction was ®nally developed as a less complex synthetic strategy. A good example is the synthesis of 6-deoxyerythronolide B (28), which bears the same 10 chiral centers as erythronolide A (compound 1a of the previous section).
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7.2 THE SYNTHESIS OF 6-DEOXYERYTHRONOLIDE |
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Scheme 7±5
6-Deoxyerythronolide B (28), produced by blocked mutants of Streptomyces erythreus, is a common biosynthetic precursor leading to erythromycins. A different route to this compound was developed with aldol methodology.5 In this approach, all the crucial C±C bond formations involved in the construction of the carbon framework are exclusively aldol reactions.
Synthesis of the macrolide 6-deoxyerythronolide B 28 is one of the successful demonstrations of double asymmetric induction applied to the construction of complicated natural products.5 Retro synthetic analysis (Scheme 7±7) shows that 28 can be obtained from thio-seco acid 29, which consists of seven propionate building blocks. This is a typical aldol product in which a boron reagent