7910
J . Am. Chem. SOC.1988, 110, 7910-7912
orientations about the (3-7bond; in one orientation N B(or N3) of His 121 could be a hydrogen bond acceptor, and in the other orientation N, (or N1) can act as a hydrogen bond donor to neighboring residues such as Glu 75, Tyr 91, and/or Tyr 93.' The direct observation of the HBprotons of histidine residues has allowed heterogeneity to be detected under conditions where it would have been missed if only the H, protons had been studied. For example, our isotopic labeling revealed heterogeneity in addition to that caused by proline isomerism',* and allowed direct observation of the H6 resonance of His 121 that could not be located in studies recently reported by Markley's l a b o r a t ~ r y .We ~ expect that the ability to detect conformational heterogeneity in SNase via both the H6and H, protons will prove useful in our studies of the effect of active site mutations on the conformations of the mutant protein^.^^^
Acknowledgment. This research was supported by GM-34573 from the National Institutes of Health to P.H.B. and J.A.G. and by PCM-8314322 from the National Science Foundation to P. H.B. (9) Cotton, F. A.; Hazen, E. E.; Legg, M. J. Proc. Nafl.Acad. Sci. U.S.A. 1979, 79, 2551-2555 (1979).
A Practical and Enantioselective Synthesis of Glycosphingolipids and Related Compounds. Total Synthesis of Globotriaosylceramide (Gb3) K. C. Nicolaou,* T. Caulfield, H. Kataoka,+ and T. Kumazawa' Department of Chemistry, University of Pennsylvania Philadelphia, Pennsylvania 19104 Received May 4, 1988 Glycosphingolipids are a class of naturally occurring bioactive compounds usually embedded in the membrane of all animal cells and in some plant cells.' The clinically important blood group antigens2 and the immunologically relevant tumor-associated oligosaccharides3 are examples of glycosphingolipids. The "intelligent" roles attributed to these biomolecules include mediation of cell-cell recognition and communication, growth regulation, and antibody interaction^.^ Due to their increasingly recognized importance in biomedical research, these molecules have attracted considerable attention from the isolation5 and 'Visiting scientist from Nippon Zeon Co., Japan, 1987-1989. f Visiting scientist from Kyowa Hakko Kogyo Co., Japan, 1987-1988. ( I ) (a) Hakomori, S . "Glycolipids of Animal Cell Membranes", In?. Rev. Sci., Org. Chem. Ser. Two 1976, 223. (b) Sharon, N.; Lis, H. Chem. Eng. News 1981,59,21. (c) Li, Y.-T.; Li, S . 4 . Adu. Carbohydr. Chem. Biochem. 1982, 40, 235. (d) Sharon, N. Trends Biochem. Sci. 1984, 9, 198. (e) Hakomori, S . Sci. Am. 1986, 154, 44. (2) (a) Marcus, D. M.; Class, L. Science (Washington, D.C.) 1969, 164, 553. (b) Hakomori, S.; Stellner, K.; Watanabe, K. Biochem. Biophys. Res. Commun.1972,49, 1061. (c) Marcus, D. M.; Nqiki, M.; Kundu, S. K. Proc. Natl. Acad. Sci. U.S.A. 1976, 73, 3263. (d) Hakomori, S.; Watanabe, K.; Laine. R. A. Pure Appl. Chem. 1977,49, 1215. (e) Niemann, H.; Watanabe, K.; Hakomori, S.; Childs, R. A.; Feizi, T. Biochem. Biophys. Res. Commun. 1978.81, 1286. (f) Watanabe, K.; Hakomori, S . ; Childs, R. A.; Feizi, T. J . Bioi. Chem. 1979, 254, 3221. (g) Feizi, T.; Childs, R. A.; Watanabe, K.; Hakomori, S. J . Exp. Med. 1979, 149, 975. (3) (a) Hakomori, S.; Andrews, H. D. Biochem. Biophys. Acta 1970,202, 225. (b) Watanabe, K.; Matsubara, T.; Hakomori, S . J. Biol. Chem. 1976. 251.2385. (c) Magnari, J. L.; Nilsson, B.; Brockhous, M.; Zopf, D.; Ginsburg, V. J. Bioi. Chem. 1982,257, 14365. (d) Hakomori, S.; Kannagi, R. J. Nufl. Cancer. I n f . 1983, 71, 231. (e) Hakomori, D.; Nudelman, E.; Levery, S. B.; Patterson, C. M. Bioi. Biophys. Res. Commun. 1983, 113, 791. (f) Kannagi, R.; Levery,, S . B.; Hakomori, S. J . Bioi. Chem. 1984, 259, 844. (4) Review: (a) Hakomori, S. Ann. Rev. Biochem. 1981, 50, 733. (b) Hakomori, S . Ann. Rev. Immunol. 1984, 2, 103. (5) (a) Hakomori, S.; Siddiqui, B.; Li, Y.-T.; Li, S.-C.; Hellerquist, C. G. J. Bioi. Chem. 1971,246,2271. (b) Hakomori, S.; Andrews, H. D. Biochem. Biophys. Acta 1970, 202, 225. (c) McKibbin, J. M.; Spencer, W. A,; Smith, E. L.; Mansson, J.-E.; Karlsson, D.-A,; Samuelsson, B. E.; Li, Y.-T.; Li, S.-C. J. Bioi. Chem. 1982, 257, 755. (d) Hakomori, S.; Patterson, C. M.;Nudelman, E.; Sekuguchi, K. J . Biol. Chem. 1983, 258, 11819.
0002-7863/88/1510-7910$01.50/0
Scheme 1"
1
I
2
rphlngorlner
cerrmldrr ly808phln~Ollpld8 glycorphlngollpldr
3:X-H,Y-Br,R.H
I
-\ I d y c
k.O/\(\i\~CW?PY
e
NHAc
E l pbUh40,
7
'Reagents and conditions: (a) 1.2 equiv of (nBu),BOTf, 1.4 equiv of Et3N, -78 OC, 30 min, then 20 OC for 2 h, added 0.75 equiv of 2 at 0 OC, 2 h, then H202/MeOH/ether. 0 OC, 1 h, 72%; (b) 2.0 equiv of NaN,, DMSO, 25 OC, 12 h, 92%; (c) 1.5 equiv of t-BuMe,SiOTf, 2.0 equiv of 2,6-lutidine, CH2Cl2, 0 "C, 2.5 h, 97%; (d) 3.0 equiv of LiBH,, T H F 0 OC, 3 h, 81%; (e) (i) 1.5 equiv of nBu4NF, T H F , 25 'C, 1 h, 90%, (ii) 10 equiv of HS(CH,),SH, 10 equiv of Et,N, MeOH, 25 OC, 24 h, (iii) 4.0 equiv of Ac20, 4.0 equiv of DMAP, CH2CI2,0 OC, 90%.
synthetic6 points of view. Despite these efforts, however, these molecules remain relatively inaccessible, particularly in homogeneous form. In this communication, we report (1) a practical, short, and enantioselective route to glycosphingolipids which can also deliver enantiomerically pure sphingosine, ceramides, lysosphingolipids,and other related derivatives and (2) a total synthesis of globotriaosylceramide (Gb3, 8) and confirmation of its structure. The strategy for the present synthesis of glycosphingolipids focuses on the asymmetric construction of the sphingosine equivalent 6 (Scheme I) following the principles advanced by Evans et aL7 and Pridgen et aL8 and its efficient and stereospecific coupling to carbohydrate fragments with the two-stage activation procedure for glycosidation recently reported from these laboratories9 (Scheme 11). The details for the synthesis of the sphingosine pregenitor 6 are shown in Scheme 1. Thus, the oxazolidinone derivative 1 was converted to its boron enolate and condensed with the a$-unsaturated aldehyde 2 to afford derivative 3'O in 72% yield." Displacement of the bromide in 3 with NaN, led to the azide 4 in 92% yield with complete inversion of stere(6) (a) Shapiro, D.; Flowers, H. M. J. Am. Chem. SOC.1961, 83, 3327. (b) Tkaczuk, P.; Thornton, E. R. J. Org. Chem. 1981, 46, 4393. (c) Mori, K.; Funaki, Y. Tetrahedron 1985, 41, 2379. (d) Sugimoto, M.; Ogawa, T. Glycoconjugate J. 1985, 2, 11. (f) Ito, Y.; Sugimoto, M.; Sato, S.; Ogawa, T. Tetrahedron Leff.1986, 27,4753. (8) Koike, K.; Sugimoto, M.; Nakahara, Y.; Ogawa, T. Carbohydr. Res. 1987,162, 237. (h) Numata, M.; Sugimoto, M.; Koike, K.; Ogawa, T. Carbohydr. Res. 1987, 163, 209. (i) Sato, S . ; Ito, Y.; Nukada, T.; Nakahara, Y.; Ogawa, T. Carbohydr. Res. 1987, 167, 197. 6 ) Schmidt, R. R.; Klager, R. Angew. Chem., In?. Ed. Engl. 1985, 24, 65. (k) Schmidt, R. R.; Zimmerman, P. Angew. Chem., I n f . Ed. Engl. 1986, 25, 725. (I) Schmidt, R. R.; Bar, T.; Apell, H. J. Angew. Chem., I n f . Ed. Engl. 1987, 26, 793. (m) Zimmermann, P.; Schmidt, R. R. Liebigs Ann. Chem. 1988,663. (n) Bar, T.; Schmidt, R. R. Liebigs Ann. Chem. 1988, 669. (0) Schmidt, R. R.; Maier, T. Carbohydr. Res. 1988, 174, 169. (p) Nimkar, S.; Menaldino, D.; Merrill, A. H.; Liotta, D. Tetrahedron Left. 1988, 29, 3037 and references cited therein. (7) Evans, D. A,; Nelson, J. V.; Voge, E.; Taber, R. R. J. Am. Chem. Soc. 1981, 103, 3099. Evans, D. A.; Sjogren, E. G.; Weber, A. E.; Conn, R. E. Tetrahedron Left. 1987, 28, 39. Evans, D. A,; Weber, A. E. J. Am. Chem. SOC.1987, 109, 7151. (8) Abdel-Magid, A.; Lantos, I.; Pridgen, L. N. Tetrahedron Lett. 1984, 25, 3273. (b) Abdel-Magid, A,; Pridgen, L. N.; Eggleston, D. S . ; Lantos, 1. J. Am. Chem. SOC.1986, 108, 4595. (9) (a) Nicolaou, K. C.; Dolle, R. E.; Papahatjis, D. P.; Randall, J. L. J. Am. Chem. SOC.1984, 106, 4189. (b) Nicolaou, K. C.; Randall, J. L.; Furst, G. T. J. Am. Chem. SOC.1985, 107, 5556. ( I O ) All new compounds exhibited satisfactory spectral and analytical and/or exact mass data. Yields refer to spectroscopically and chromatographically homogeneous materials. ( I I ) In addition to compound 3, a second product, presumed to be the other syn diastereoisomer of 3, was obtained in ca. 5% yield.
0 1988 American Chemical Society
J . A m . Chem. SOC.,Vol. 110, No. 23, 1988 791 1
Communications to the Editor Scheme 11'
bohydrate donors. Thus, gala~tosylceramide,'~ lactosylceramide,I5 and globotriaosylceramide (Gb3, 8)16were synthesized from 6 and
PhCyo
OCH2Ph
OH-
P hPhCHp C H f l k F
OH
SPh R.0
9
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