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Introduction

Introduction. 細胞表面糖鎖の役割. 細菌 ウイルス 毒素. 栄養・老廃物. シアル酸. 細胞間の情報伝達 細胞内外の連絡 組織の形成 細胞外からの情報受信（毒素の感知） 細菌・ウイルスなどの感染部位 異物認識・記憶など. Naturally occurring 36 sialic acids. N -Acetyl-sialic acids 19. N -Glycolyl-sialic acids 16. Deamin o- sialic acid.

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Introduction

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  1. Introduction

  2. 細胞表面糖鎖の役割 細菌 ウイルス 毒素 栄養・老廃物 シアル酸 細胞間の情報伝達 細胞内外の連絡 組織の形成 細胞外からの情報受信（毒素の感知） 細菌・ウイルスなどの感染部位 異物認識・記憶など

  3. Naturally occurring 36 sialic acids N-Acetyl-sialic acids 19 N-Glycolyl-sialic acids 16 Deamino-sialic acid Schauer, R. Kelmm S., Reuterm G, Roggentin, P. and ShawL (1995) Biochemistry and role of sialic acids. 7-64 Biology of the sialic acids Rosenberg (ed). Ogura, H. (1994) Search for physiological active substances starting from sialic acid as a leading compound. YAKUGAKU ZASSHI, 114, 277-303. Ogura, H. (2005) Sialic acids. Key, Tokyo.

  4. シアル酸 単体として存在するほか 複合糖質の構成成分 細胞膜表面のオリゴ糖の末端にあって 重要な生物学的機能をもつ Mr. SIALIC ACIDS（Prof. Roland Schauer） ◎　生命現象の基本的な言語 ①　核酸 ②　タンパク質 ③　シアル酸誘導体 ④　脂質

  5. シアル酸の歴史 • 糖脂質の研究（E. Klenk）1935-1939Tay-Sacks, Niemann-Pick • 糖タンパク質の研究（G. Blix）1938　ウシの脳 • ビアル試薬陽性物質　エールリッヒ試薬 • 　　　「シアル酸 p.38」　　　　　　　　　　　　　　　　　　　　　 • ヘマタミン酸　1950　山川会長　ウマの赤血球膜から • 名称の統一　1957年　ブリックス、ゴットシャーク、クレンク • KDNなど

  6. シアル酸の歴史 Faillard, H. (1988) The early history of sialic acids. Schauer. R. and Yamakawa, T. (eds.) Sialic acid. Bärbel, Mende, Kiel pp. 6-18.

  7. シアル酸研究への道筋 E. Ochiai and H. Ogura “Polarisation der heterocyklishem Ringe mit aromatishem Charakter. Uber die Nitrierung des 4-Oxychinolin-N-oxydes und das Verhalten des 4-Nitrochinolin-N-oxydes gegen Essigsaureanhydrid” J. Pharm. Soc. Japan, 72, 767-771 (1952). 薬学博士東京大学：　津田恭介　教授　（1959） 北里大学薬学部教授：　（1964） 　　ヘテロ環の化学 　　ラクタム、マクロライドの立体化学 　　官能基の活性化試薬 　　変型ヌクレオシドの合成 　　シアル酸誘導体の合成と立体化学

  8. シアル酸研究への道筋

  9. シアル酸研究への道筋 立体化学と創薬 Stereochemistry of Sialic Acids, and their deivatives GLYCOLIPOID The 2nd International Meeting of Sialic Acids Society, October 13, 1986 In essence, “sialic acid derivatives possess a harmonious shape and good balance between two opposing hydrophilic and hydrophobic parts, meaning that they should display various kinds of potentially unique and possibly conflicting physiological activities (glycolipoids)”. Consequently, there are good omens that unprecedented ‘miracle’ medicines could be developed from sialic acid derivatives.

  10. 研究に使用したシアル酸 Ogura, H. (1992) Sialic acid derivatives as glycolipoids. Ogura, H., Hasegawa, A. and Suami, T. (eds.) Carbohydrate –Synthetic Methods and Applications in Medicinal Chemistry. Kodansha–VCH, Tokyo Ogura, H. (1994) Search for physiological active substances starting from sialic acid as a leading compound. YAKUGAKU ZASSHI, 114, 277-303. Ogura, H. (2005) Sialic acids. Key, Tokyo. Fig. 1 Typical sialic acids

  11. H. Ogura, H. and Furuhata, K. (1981) Determination of anomeric configuration of neuraminic acid derivatives by circular dichroism. Tetrahedron Lett., 22, 4265-4268. Ogura, H., Furuhata, K., Saito, H., Izumi, G., Itoh, M. and Shitori, Y. (1984) Stereochemical characterization of hydrated and dehydrated crystals of N-acetylneuraminic acid as revealed by the IR, CD, and 13C cross polarization- magic angle spinning NMR spectroscopy. Chem. Lett., 1003-1006. Fig. 2 Equilibrium of Neu5Ac

  12. Schauer. R. (2004) Sialic aids: fasinating sugars in higher animals and man. Zoology, 108, 49-64. Ogura, H., Furuhata, K., Itoh, M. and Shitori, Y. (1988) N-Glycolyl- neuraminic acid and its derivatives. JP 63-28429, 233-236. [Chem. Abstr., 108, 56543v] Fig. 3 Sylnthesis of Neu5Gc

  13. 官能基活性化試薬 a) Ogura, H., Kobayashi, T., Shimizu, K., Kawabe, K. and Takeda, K. (1979) A novel active ester synthesis reagent (N,N’-disuccinimidyl carbonate). Tetrahedron Lett., 4745-4746. b) Ogura, H., Nagai, S. and Takeda, K. (1980) A novel reagent (N-succinimidyl diphenylphosphate) for synthesis of active ester and peptide. Tetrahedron Lett., 21, 1467-1468. c) Ogura, H. and Takeda, K. (1981) Novel reagents (disuccinimido carbonate: succinimido diphenyl phos- phate) for synthesis of active ester and peptide. Nihon Kagaku Kaisi (Journal of the Chemical Society of Japan, Chemistry and Industrial Chemistry), 5, 836-844. d) Takeda, K., Sawada, I., Suzuki, A. and Ogura, H. (1983) A convenient synthesis of peptide using oxallates. Tetrahedron Lett., 24, 4451-4454. e) Ogura, H. and Takeda, K. (1981) A convenient synthesis of lactam rings. Heterocyles, 15, 467-468. f) Takeda, K. and Ogura, H. (1986) Symmetric oxalates as active esterification reagent for activated ester – N,N’-disuccinimidyl oxalate (DSO) –. Journal of Synthetic Organic Chemistry Japan, 44, 1182-1187. Fig. 4 Sylnthesis of DSC

  14. Nakamura, M., Furuhata, K. Yamazaki, K., Ogura, H., Kamiya, H. and Ida, H. (1989) Isolation of 3-deoxy-D-glycero-D-galacto-2-nonulopyranosonic acid (KDN) from chum salmon, oncorhynchus keta. Chem. Pharm. Bull., 37, 2204- 2206. Shirai, R., Nakamura, M., Hara, S., Takayanagi, H. and Ogura, H. (1988) Thermal rearrangement of N-acetyl-N-nitrosoneuraminic acid derivative: Synthesis of 3-deoxy-D-nonulosonic acid (KDN). Tetrahedron Lett., 29, 4449- 4452. Fig. 5 Sylnthesis of KDN from Neu5Ac by thermal rearrangement

  15. Shirai, R. and Ogura, H. (1989) Improved synthesis of two 3-deoxy- ald-2-ulosonic acid (KDN, KDO) by condensation of oxalacetic acid with aldoses followed by Ni2+ catalyzed decarboxylation. Tetrahedron Lett., 30, 2263-2264. Nakamura, M., Takayanagi, H., Furuhata, K. and Ogura, H. (1992) Synthesis and characterization of furanose and pyranose derivatives of 3-deoxy-D-glycero- D-galacto-2-nonulopyranosonic acid (KDN). Chem. Pharm. Bull., 40, 879-885. Fig. 6 Sylnthesis of KDN and KDO

  16. Nakamura, M., Takayanagi, H., Furuhata, K. and Ogura, H. (1992) Synthesis and characterization of furanose and pyranose derivatives of 3-deoxy-D-glycero- D-galacto-2-nonulopyranosonic acid (KDN). Chem. Pharm. Bull., 40, 879-885. Fig. 7 Methylation of KDN and KDO

  17. Fig. 8 Equilibrium of KDN

  18. Furuhata, K., Sato, S., Goto, M., Takayanagi, H. and Ogura, H. (1988) The crystal and molecular structure of N-acetyl-2,3-dehydroxy-2-deoxy-neuraminic acid. Chem. Pharm. Bull., 36, 1872-1876. A perspective view of Neu2en5Ac (4) Fig. 9 Synthesis of Neu2en5Ac

  19. Ogura, H. (1986) Chemistry and applications of sialic acids. Finechemical, ’86-15, 47-59. Fig. 10 Reaction of Neu2en5Ac

  20. 5-Me • Suzuki, M., Suzuki, A., Yamakawa, T. and Matsunaga, E. (1985) Characterization of 2,7-anhydro-N-acetylneuraminic • acid in human wet cerumen. J. Biol. Chem., 97, 509-515. b) Li, Y.-T., Nakagawa, H., Hansson, G. C. and Li, S.-C., (1990) A novel sialidase which releases 2,7-anhydro-N-acetylneuraminic acid from sialoglycoconjugates. J. Bol. Chem., 265, 21629-21633. • c) Takeda, K., Tuboyama, K., Torii, K., Furuhata, K., Sato, N. and Ogura, H. (1990) A convenient synthesis of S-glycosyl donors of sialic acid and their use for O-glycosylation. Carbohydr. Res., 203, 57-63. • d) Furuhata, K., Takeda, K. and Ogura, H. (1991) Synthesis of 2,7-anhydro- N-acetylneuraminic acid. Chem. Pharm. Bull., 39, 817- 819. • e) Takeda, K., Tsuboyama, K., Hoshino, M., Kishino, M. and Ogura, H. (1987) A synthesis of a new type of alkoxycarbonylating reagents from 1,1-bis- [6-(trifluoromethyl)benzothiazolyl] carbamate (BTBC) and their reactions. • Synthesis, 557-560. • f) Takeda, K., Tsuboyama, K., Takayanagi, H. and Ogura, H. (1987) S,S’-Bis(1-phenyl-1H-tetrazol-5-yl) dithiocarbonate: a new esterification reagent. Synthesis, 560-562. Fig. 11 Synthesis of 2,7-anhydro-N-acetylneuramnic acid

  21. Furuhata, K. and Ogura, H. (1992) Synthesis of 2,7-anhydrosialic acids. Chem. Pharm. Bull., 40, 3197-3200. Fig. 12 Synthesis of 2,7-anhydro-N-glycolylneuramnic acid

  22. シアル酸誘導体の合成 a) Ogura, H., Furuhata, K., Itoh, M. and Shitori, Y. (1986) Syntheses of 2-O-glycosyl derivatives of N-acetyl-D-neuraminic acid. Carbohydr. Res., 158, 37-51. b) Furuhata, K., Sato, S., Anazawa, K., Goto, K., Takayanagi, H. and Ogura, H. (1987) The 1,4-lactone derivatives of N-acetylneuraminic acid. Chem. Pharm. Bull., 35, 3609-3614. c) Sato, S., Furuhata, K. and Ogura, H. (1988) Lactone derivatives of N-acetyl- neuraminic acid. Chem. Pharm. Bull., 36, 4678-4688. Fig. 13 Esterification of Neu5Ac

  23. Furuhata, K., Sato, S., Anazawa, K., Goto, K., Takayanagi, H. and Ogura, H. (1987) The 1,4-lactone derivatives of N-acetylneuraminic acid. Chem. Pharm. Bull., 35, 3609-3614. Fig. 14 A perspective view of 5-aetamido-6,7,8,9-tetra-O-acetyl- 2-O-methyl-3,5-dideoxy-ß-D-glycero-D-galacto-2-noneno- 1,4-lactone (45)

  24. Neu5Ac のアシル化反応 Sugiyama, N., Sugai, K., Yamada, N., Goto, M., Ban, C., Furuhata, K., Takayanagi, H. and Ogura, H. (1988) Formation of a 1,7-lactone derivative by direct acetylation of N-acetylneuraminic acid. Chem. Pharm. Bull., 36, 1147-1152. Fig. 15 Acetylation of Neu5Ac

  25. Fig. 16 A perspective view of 5-aetamido-2,4,8,9-tetra-O-acetyl- 3,5-dideoxy-ß-D-glycero-D-galacto-2-nonulopyranosono- 1,7-lactone (49)

  26. Neu5Ac のアシル化反応 Sato, S., Furuhata, K. and Ogura, H. (1988) Lactone derivatives of N-acetyl- neuraminic acid. Chem. Pharm. Bull., 36, 4678-4688. Fig. 17 Acylation of Neu5Ac

  27. Neu5Ac のアシル化反応 Ogura, H., Furuhata, K., Sato, S., Anazawa, K., Itoh, M. and Shitori, Y. (1987) Synthesis of 9-O-acetyl- and 4-O-acetyl-sialic acids. Carbohydr. Res., 167, 77-86. Fig. 18 Acetylation of 4-position

  28. Neu5Ac のアシル化反応 Anazawa, K., Furuhata, K. and Ogura, H. (1988) Synthesis of 7-O-acetyl-N-acetylneuraminic acid derivative. Chem. Pharm. Bull., 36, 4976-4979. Fig. 19 Acetylation of 7-position

  29. Neu5Ac のアシル化反応 Ogura, H., Furuhata, K., Sato, S., Anazawa, K., Itoh, M. and Shitori, Y. (1987) Synthesis of 9-O-acetyl- and 4-O-acetyl-sialic acids. Carbohydr. Res., 167, 77-86. Fig. 20 Acylation of 9-position

  30. Neu5Ac のグリコシル化反応：　グリコシルドナーの合成 Ogura, H., Furuhata, K., Itoh, M. and Shitori, Y. (1986) Syntheses of 2-O-glycosyl derivatives of N-acetyl-D-neuraminic acid. Carbohydr. Res., 158, 37-51. Fig. 21 Synthesis of glycosyl donor

  31. 官能基活性化試薬 a) Takeda, K., Tsuboyama, K., Takayanagi, H. and Ogura, H. (1987) S,S’-Bis(1-phenyl-1H-tetrazol-5-yl) dithiocarbonate: a new esterification reagent. Synthesis, 560-562. b) Takeda, K., Tsuboyama, K., Torii, K. Murata, M. and Ogura, H. (1988) Single-step preparation of allylic sulfides having 1-phenyl-tetrazole-5-thio group from allylic alchols using S,S’-bis(1-phenyl-1H-tetrazol-5-yl) dithio-carbonate and reactions involving the allylic sulfides. Tetrahedron Lett., 29, 4105-4108. c) Tsuboyama, K., Takeda, K., Torii, K. and Ogura, H. (1990) Convenient synthesis of allylic sulfides and application to allylic carbon-carbon bond formation. Chem. Pharm. Bull., 38, 2357-2363. Fig. 22 Synthesis of S,S’-bis(1-phenyl-1H-tetrazol-5-yl)dithiocarbonate (30) and its reactions

  32. 官能基活性化試薬 a) Takeda, K., Torii, K. and Ogura, H. (1990) Silver triflate-promoted coupling reactions of benzylic and allylic sulfides with O-sillylated enolates of ketones and esters, a synthesis of (+-)-AR-turmerone. Tetrahedron Lett., 31, 265-266. b) Tsuboyama, K., Takeda, K., Torii, K., Ebihara, M., Shimizu, J., Suzuki, A. and Ogura, H. (1990) A convenient synthesis of S-glycosyl donors of D-glucose and O-glycosylations invoving the new reagent. Chem. Pharm. Bull., 38, 636-638. c) Takeda, K., Tuboyama, K., Torii, K., Furuhata, K., Sato, N. and Ogura, H. (1990) A convenient synthesis of S-glycosyl donors of sialic acid and their use for O-glycosylation. Carbohydr. Res., 203, 57-63. Fig. 23 Synthesis of S-glycosyl donor

  33. Neu5Ac のグリコシル化反応 Sato, S., Furuhata, K., Itoh, M., Shitori, Y. and Ogura, H. (1988) Synthesis of 2-O-glycosyl derivatives of N-acetylneuraminic acid. Chem. Pharm. Bull., 36, 914-919. Fig. 24 Dissacharide nucleoside of Neu5Ac (1)

  34. Neu5Ac のグリコシル化反応 a) Ogura, H., Furuhata, K., Itoh, M. and Shitori, Y. (1986) Syntheses of 2-O-glycosyl derivatives of N-acetyl-D-neuraminic acid. Carbohydr. Res., 158, 37-51. b) Sato, S., Furuhata, K., Itoh, M., Shitori, Y. and Ogura, H. (1988) Synthesis of 2-O-glycosyl derivatives of N-acetylneuraminic acid. Chem. Pharm. Bull., 36, 914-919. Fig. 25 Dissacharide nucleoside of Neu5Ac (2)

  35. Neu5Ac のグリコシル化反応 Ogura, H., Fujita, H., Furuhata, K., Itoh, M. and Shitori, Y. (1986) Synthesis of N-acetyl-D-neuraminic acid N-nucleoside analogs. Chem. Pharm. Bull., 34, 1479-1484. Fig. 26 N-glycoside nucleoside

  36. Neu5Ac のグリコシル化反応 Ogura, H. and Furuhata, K. (1984) Syntheses of sialic acid derivatives. Journal of Synthetic Organic Chemistry Japan, 42, 536-543. Fig. 27 Synthesis of mucin analogs

  37. Neu5Ac のグリコシル化反応 Furuhata, K., Anazawa, K., Itoh, M., Shitori, Y. and Ogura, H. (1986) Synthesis of a- and ß-D-Neu5Acp-(2→6)-lactose.Chem. Pharm. Bull., 34, 2725-2731. Fig. 28 Synthesis of Neu5Ac(2→6)lactose and 9-O-acyl derivatives

  38. Neu5Ac のグリコシル化反応 Sato, S., Fujita, S., Furuhata, K., Ogura, H., Yoshimura, S., Itoh, M. and Shitori, Y. (1987) Synthesis of 2-(5-cholesten-3ß-yloxy) glycosides of N-acetyl-D- neuraminic acid derivatives. Chem. Pharm. Bull., 35, 4043-4048. Fig. 29 Synthesis ofsialyl cholesterol

  39. Neu5Ac のグリコシル化反応 Suzuki, K., Kobayashi, R., Furuhata, K. and Ogura, H. (1990) Synthe-sis of 6-O-(5-acetamido-3,5-dideoxy-D-glycero-a- and -ß-D-galacto-nonulopyranosonic acid)-(2→6)-O-ß-D-galactopyranosyl-(1→4)-1-(5-cholesten-3ß-yloxy)-ß-D-gluco-pyranose. Chem. Pharm. Bull., 38, 2083-2087. Fig. 30 Synthesis ofGM3 analog

  40. Neu5Ac のグリコシル化反応 Furuhata, K. and Ogura, H. (1989) Synthesis of partially O-acetylated 4-methylcoumaryl 5-acetamido-3,5-dideoxy-a-D-glycero-D-galacto-2-nonulopyranosidonic acids. Chem. Pharm. Bull., 37, 2037- 2040. Fig. 31 Synthesis ofpartially acetylated 4-methylcoumarin derivatives

  41. Neu5Ac のグリコシル化反応 Furuhata, K. and Ogura, H. (1989) Synthesis of partially O-acetylated 4- methylcoumaryl 5-acetamido-3,5-dideoxy-a-D-glycero-D-galacto-2-nonulopyran- osidonic acids. Chem. Pharm. Bull., 37, 2037- 2040. Fig. 31 Synthesis ofpartially acetylated 4-methylcoumarin derivatives

  42. Neu5Ac のグリコシル化反応 Furuhata, K., Komiyama, K., Takeda, K., Takayanagi, H., Torii, K., Mishima, K., Ogura, H. and Hata, T. (1989) Reaction of glycosyl halides with 7-hydroxy- 9a-methoxymitosane sodium salt. Chem. Pharm. Bull., 37, 2651-2654. Furuhata, K., Komiyama, K., Ogura, H. and Hata, T. (1991) Studies on glycosylation of the mitomycins. The structures of 7-N-(4-O-glycosyl-phenyl)- 9a-methoxymitosanes. Chem. Pharm. Bull., 39, 255-259. Fig. 32 Glycosylation of mitomycins

  43. KDN のグリコシル化反応 Perspective view of 130a,b and 131a,b Nakamura, M., Takayanagi, H., Furuhata, K. and Ogura, H. (1992) Synthesis and characterization of furanose and pyranose derivatives of 3-deoxy-D-glycero- D-galacto-2-nonulopyranosonic acid (KDN). Chem. Pharm. Bull., 40, 879-885. Fig. 33 Fischer’s methyl glycosylation of KDN

  44. KDN のグリコシル化反応 Nakamura, M., Takayanagi, H., Furuhata, K. and Ogura, H. (1992) Synthesis and characterization of furanose and pyranose derivatives of 3-deoxy-D-glycero- D-galacto-2-nonulopyranosonic acid (KDN). Chem. Pharm. Bull., 40, 879-885. Fig. 34 Acetylation ofKDN

  45. KDN のグリコシル化反応 a) Nakamura, M., Furuhata, K. and Ogura, H. (1988) Synthesis of a- and ß-O- glycosides of 3-deoxy-D-glycero-D-galacto-2- nonulopyranosonic acid (KDN). Chem. Pharm. Bull., 36, 4807-4813. b) Nakamura, M., Furuhata, K. and Ogura, H. (1989) Synthesis of aryl-a- glycosides of 3-deoxy-D-glycero-D-galacto-2-nonulopyranosonic acid (KDN). Chem. Pharm. Bull., 37, 821-823. c) Nakamura, M., Fujita, S., Furuhata, K., and Ogura, H. (1991) Synthesis of the nucleoside analogues of 3-deoxy-D-glycero-D-galacto-2-nonulo-pyranosonic acid (KDN). Nucleic Acids, S25, 137-138. d) Nakamura, M., Furuhata, K., Yamasaki, T. and Ogura, H. (1991) Synthesis of the a- and ß-N-glycosides of 3-deoxy-D-glycero-D-galacto-2-nonulopyranosonic acid (KDN). Chem. Pharm. Bull., 39, 3140-3144. Fig. 35 Glycosylation of KDN

  46. KDN のグリコシル化反応 Perspective view of 143 (R=Me. R’=H) Nakamura, M., Fujita, S., Furuhata, K., and Ogura, H. (1991) Synthesis of the nucleoside analogues of 3-deoxy-D-glycero-D-galacto-2-nonulo-pyranosonic acid (KDN). Nucleic Acids, S25, 137-138. Fig. 36 N-Glycosylation of KDN

  47. KDN のグリコシル化反応 Sun, X-L., Haga, N., Ogura, H. and Takayanagi, H. (1994) Synthesis of a-N-glycosides of 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) using nucleobases and their photocycloaddition to 2,3-dimethyl-2-butene. Chem. Pharm. Bull., 42, 2352-2356. Fig. 37 Photocycloaddition of 2,3-dimethyl-2-butene

  48. KDN のグリコシル化反応 a) Haga, N., Ishikawa, I., Kinumura, M., Takayanagi, H. and Ogura, H. (1993) Photocycloaddition of 2’-deoxyribo- nucleoside to 2,3-dimethyl-2-butene. Hetero- cycles, 35, 569-572. b) Haga, N. and Ogura, H. (1993) Photocycloaddition of cytosine and 2’- deoxycytidines to 2,3-dimethyl-2-butene. Heterocycles, 36, 1721-1724. c) Haga, N., Ishikawa, I., Takayanagi, H. and Ogura, H. (1994) Photo- cycloaddition of deoxyuridines to 2,3-dimethyl-2-butene. Bull. Chem. Soc. Jpn., 67, 728-737. d) Li, S. S., Sun, X. L., Ogura, H., Konda, Y., Sasaki, T., Toda, Takayanagi, H. and Harigaya, Y. (1995) Photocycloaddition of benzoylated 2’-deoxyribonucleo- side to 2,3-dimethyl-2-butene. Chem. Pharm. Bull., 43, 144-146. e) Haga, N., Kuriyama, Y., Takayanagi, H., Ogura, H. and Tokumaru, K. (1995) Kinetics and mechanism of photocycloaddition of deoxyuridines to 2,3-dimethyl- 2-butene. Photochemistry and Photobiology. 61, 557-562. Fig. 38 Glycosylation of KDN with BDTC

  49. Stereochemistry H-3eq (d; ppm) of sialic acids derivatives a) Ogura, H., Furuhata, K., Sato, S., Anazawa, K., Itoh, M. and Shitori, Y. (1987) Synthesis of 9-O-acetyl- and 4-O-acetylsialic acids. Carbohydr. Res., 167, 77-86. b) Takeda, K., Tuboyama, K., Torii, K., Furuhata, K., Sato, N. and Ogura, H. (1990) A convenient synthesis of S-glycosyl donors of sialic acid and their use for O-glycosylation. Carbohydr. Res., 203, 57-63

  50. Stereochemistry a) Ogura, H. and Furuhata, K. (1981) Determination of anomeric configuration of neuraminic acid derivatives by circular dichroism. Tetrahedron Lett., 22, 4265-4268. b) Ogura, H., Furuhata, K., Saito, H., Izumi, G., Itoh, M. and Shitori, Y. (1984) Stereochemical characterization of hydrated and dehydrated crystals of N-acetylneuraminic acid as revealed by the IR, CD, and 13C cross polarization- magic angle spinning NMR spectroscopy. Chem. Lett., 1003-1006. Fig. 39 CD spoectra of sialic acids (a) Neu5Ac and its a- and b-methyl glycosides

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