A General Synthesis of Iminosugars Ciaran McDonnell, Linda Cronin, Julie L. O’Brien, and Paul V. Murphy* Centre for Synthesis and Chemical Biology, Chemistry Department, Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland
of synthetic routes to azasugars published to date.7 Herein, we describe a general approach for the synthesis of 1-deoxyazasugars.8 More specifically, the synthesis of 1-deoxynojirimycin 1, 1-deoxymannojirimycin 2,9 1-deoxygalactostatin 3, and 1,6-dideoxygalactostatin 410 has been achieved from the corresponding 6-deoxyhex-5-enopyranosyl azide.11
[email protected] Received December 2, 2003
Abstract: 1-Deoxynojirimycin, 1-deoxymannojirimycin, and 1-deoxygalactostatin have been synthesized by epoxidation of tri-O-acetyl-6-deoxyhex-5-enopyranosyl azides followed by methanolysis, deacetylation, and catalytic hydrogenation. 1,6-Dideoxygalactostatin was obtained by the reaction of 2,3,4-tri-O-acetyl-6-deoxy-β-L-arabino-hex-5-enopyranosyl azide with NIS in methanol followed by deacetylation and catalytic hydrogenation. The overall yields were 4.4-23.5% over seven to nine steps.
The iminosugars (“azasugars”) are a family of polyhydroxylated heterocycles containing an endocyclic nitrogen atom, and some are naturally occurring. 1-Deoxynojirimycin 1 is an example of a naturally occurring azasugar,1 and derivatives have found clinical application.2 In general, these compounds are among the most promising lead compounds for treatment of HIV infection, hepatitis C virus infection, diabetes, and other metabolic disorders.3 The substitution of the ring oxygen of the corresponding pyranose with the nitrogen renders the azasugar metabolically inert but does not prevent their recognition by glycosidases4 and glycosyltransferases,5 and they can therefore inhibit glycoprocessing. The carbohydrate mimicry displayed by azasugars has resulted in their use as tools in the investigation of glycoprotein maturation and in the study of certain biochemical pathways. The mechanism of inhibition of glycosidases displayed by these derivatives is due to their binding in the enzyme active site. The azasugars are charged at physiological pH, and the interaction of the charged nitrogen with carboxylates involved in catalysis is important. There is evidence that the anti HIV-1 activity displayed by some of these molecules may be due to inhibition by the azasugars at novel and as yet undetermined sites of action.6 There have been a number (1) Asano, N.; Nash R. J.; Molyneaux, R. J.; Fleet, G. W. J. Tetrahedron: Asymmetry 2000, 11, 1645. (2) Kingma, P. J.; Menheere, P. P.; Sels, J. A.; Nieuwenhuijzen Kruseman, A. C. Diabetes Care 1992, 15, 478. (3) (a) Hughes, A. B.; Rudge, A. J. Nat. Prod. Rep. 1994, 135. (b) Winchester, B.; Fleet, G. W. J. Glycobiology 1992, 2, 199. (4) For reviews on glycosidase inhibition see refs 1 and 3 and: (a) Ganem, B. Acc. Chem. Res. 1996, 29, 340. (b) Heightman, T. D.; Vasella A. T. Angew. Chem., Int. Ed. 1999, 38, 750. (c) Lillelund V. H.; Jensen, H. H.; Liang, X.; Bols, M. Chem. Rev. 2002, 102, 515. (d) Greimel, P.; Spreitz, J.; Stutz, A. E.; Wrodnigg, T. M. Curr. Topics. Med. Chem. 2003, 3, 513. (5) For a recent review on iminosugar based glycosyltransferase inhibitors, see: Compain, P.; Martin, O. R. Curr. Top. Med. Chem. 2003, 3, 541.
Retrosynthetic Analysis. We have studied the preparation and reactions of epoxides derived from 6-deoxyhex(6) Asano, N.; Nishida, M.; Kato, A.; Kizu, H.; Matsui, K.; Shimida, Y.; Itoh, T.; Baba, M.; Watson, A. A.; Nash, R. J.; de Q. Lilley, P. M.; Watkin, D. J.; Fleet, G. W. J. J. Med. Chem. 1998, 41, 2565. (7) For selected reviews on synthesis of glycosidase inhibitors, see: (a) Tatsuta, K. In Carbohydrate Mimics; Chapleur, Y., Ed.; WileyVCH: Weinheim, 1998; pp 283-305. (b) Fechter, M. H.; Stu¨tz, A. E.; Tauss, A. Curr. Org. Chem. 1999, 3, 269. (8) For general approaches to iminosugars, see: (a) Kajimoto, T.; Chen, L. R.; Liu, K. K. C.; Wong, C. H. J. Am. Chem. Soc. 1991, 113, 6678. (b) LeMerrer, Y.; Poitout, L.; Depezay, J. C.; Dosbaa, I.; Geoffroy, S.; Foglietti, M. J. Bioorg. Med. Chem. 1997, 5, 519. (c) Singh, O. V.; Han, H. Tetrahedron Lett. 2003, 44, 2387. (d) Baxter, E. W.; Reitz, A. B. J. Org. Chem. 1994, 59, 3175. (9) For previous syntheses of 1 and/or 2, see refs 3 and 7 and: (a) Rudge, A. J.; Collins, I.; Holmes, A. B.; Baker. R. R. Angew. Chem., Int. Ed. Engl. 1994, 33, 3, 2320. (b) Schaller, C.; Vogel, P.; Ja¨ger, V. Carbohydr. Res. 1998, 314, 25. (c) Johnson, C. R.; Nerurkar, B. M.; Golebiowski, A. Sundram, H.; Esker, J. L. J. Chem. Soc. Chem. Commun. 1995, 1139. (d) Lindstrom, U. M.; Somfai, P. Tetrahedron Lett. 1998, 39, 7173. (e) Comins, D. L.; Fulp, A. B.; Tetrahedron Lett. 2001, 42, 6839. (f) Matos, C. R. R.; Lopes, R. S. C.; Lopes, C. C. Synthesis 1999, 571. (g) Kajimoto, T.; Liu, K. K. C.; Pederson, R. L.; Zhong, Z. Y.; Ichikawa, Y.; Porco, J. A.; Wong, C. H. J. Am. Chem. Soc. 1991, 113, 6187. (h) Cook, G. R.; Beholz, L. G.; Stille, J. R. J. Org. Chem. 1994, 59, 9, 3575. (i) Xu, Y.-M.; Zhou, W.-S. J. Chem. Soc., Perkin Trans. 1 1997, 741. (j) Haukaas, M. H.; O’Doherty, G. A. Org. Lett. 2001, 3, 401. (k) Johnson, C. R.; Golebiowski, A.; Schoffers, E.; Sundram, H.; Braun, M. P. Synlett, 1995, 313. (l) Furneaux, R. H.; Tyler, P. C.; Whitehouse, L. A. Tetrahedron Lett. 1993, 34, 3613. (m) Zhous, P. Z.; Salleh, H. M.; Chan, P. C. M.; Lajoie, G.; Honek, J. F.; Nambiar, P. T. C.; Ward, O. P. Carbohydr. Res. 1993, 239, 155. (n) Yokoyama, H.; Otaya, K.; Kobayashi, H.; Miyazawa, M.; Yamaguchi, S.; Hirai, Y. Org. Lett. 2000, 2, 2427. (o) Martı´n, R.; Moyano, A.; Pericas, Riera, A. Org. Lett. 2000, 2, 93. (p) Knight, J. G.; Tchabanenko, K.; Tetrahedron 2003, 59, 281. (q) Meyers, A. I.; Andres, C. J.; Resek, J. E.; Woodall, C. C.; McLaughlin M. A.; Lee, P. H.; Price, D. A. Tetrahedron 1999, 55, 8931. (r) Spreitz, J.; Stutz, A. E.; Wrodnigg, T. M. Carbohydr. Res. 2002, 337, 183. (s) Straub, A.; Effenberger, F.; Fischer, P. J. Org. Chem. 1990, 55, 3929. (10) For previous syntheses of 3 and/or 4, see: (a) Paulsen, H.; Hayauchi, Y.; Sinnwell, V. Chem. Ber. 1980, 113, 2001. (b) Lees, W. J.; Whitesides, G. M.; Bioorg. Chem. 1992, 20, 173. (c) Kajimoto, T.; Chen, L.; Liu, K. C.; Wong, C. H. J. Am. Chem. Soc. 1991, 113, 6678. (d) Liu, K. C.; Kajimoto, T.; Chen, L.; Zhong, Z.; Ichikawa, Y.; Wong, C. H. J. Org. Chem. 1991, 56, 6280. (d) Aoyagi, S.; Fujimaki, S.; Yamazaki, N.; Kibayashi, C. J. Org. Chem. 1991, 56, 815. (e) Furneaux, R. H.; Tyler, P. C.; Whitehouse, L. A., Tetrahedron. Lett. 1993, 34, 22, 3609. (f) Asano, K.; Hakogi, T.; Iwama, S.; Katsumura, S., Chem. Commun. 1999, 1, 41. (g) Uriel, C.; Santayo-Gonzalez, F. Synlett 1999, 5, 593. (h) Ruiz, M.; Ruanova, T. M.; Ojea, V.; Quintela, J. M. Tetrahedron. Lett. 1990, 40, 2021. (j) Barilli, P. L.; Berti, G.; Catelani, G.; D’Andrea, F.; De Rensis, F.; Puccioni, L. Tetrahedron 1997, 53, 3407. (k) Chida, N.; Tanikawa, T.; Tobe, T. Ogawa, S. J. Chem. Soc., Chem. Commun. 1994, 1247. (l) Shivlock, J. P.; Fleet, G. W. J. Synlett 1998, 554. Kiguchi, T.; Tajiri, K.; Ninomiya, I.; Naito, T. Tetrahedron 2000, 56, 5819. (m) Takahata, H.; Banba, Y.; Ouchi, H.; Nemoto, H. Org. Lett. 2003, 5, 2527. (n) Defoin, A. Sarazin, H.; Streith, J. Synlett 1995, 1187. (o) Defoin, A.; Sarazin, H.; Streith, J. Tetrahedron 1997, 53, 13783. (11) A preliminary account of the work described herein has been published. See: Tosin M.; O’Brien, J.; Murphy, P. V. Org. Lett. 2001, 3, 3353.
10.1021/jo035763u CCC: $27.50 © 2004 American Chemical Society
Published on Web 04/07/2004
J. Org. Chem. 2004, 69, 3565-3568
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SCHEME 1. Retrosynthetic Analysis
5-enopyranosides (similar to 8) and found they are hydrolyzed to give 1,5-dicarbonyl sugars.12 Baxter and Reitz have previously converted such 1,5-dicarbonyl sugars to azasugars by a double-reductive amination strategy.4d It seemed reasonable that the imine 6, which is presumably related to intermediates generated by the Baxter and Reitz approach, would be generated in situ by catalytic hydrogenation of 7 and that further reduction in situ would give 1-deoxyazasugars via the cyclic imine 5 (Scheme 1).13 It was anticipated that 7 would be accessible from the alkene 8 and its epoxide derivatives. Synthesis of 1-Deoxymannojirimycin and 1Deoxynojirimycin. The alkene 10a, required for synthesis of 1-deoxymannojirimycin, was obtained after the acetolysis of 9a14 followed by reaction of the product with azidotrimethylsilane and tin(IV) chloride and subsequent elimination of hydrogen iodide using DBU.15 A similar sequence from the corresponding glucopyranoside 9b gave the alkene 10b. It was possible to isolate in good yields mixtures of epoxides 11a and 11b16 from reactions of methyl(trifluoromethyl)dioxirane, generated in situ,17 with 10a and 10b. Prolonged reaction times or attempts to separate the diastereoisomeric epoxides by chromatography led to the formation and isolation of hexos-5uloses 15,12 resulting from the hydrolysis of the epoxide and subsequent elimination of hydrogen azide. The reaction of methanol with epoxides 11a gave, with high stereoselectivity, the intermediate 13; this results from attack by the nucleophile at C-5 and subsequent migration of the acetate group from O-4 to O-6 during chromatography. The product adopts the 1C4 conformation (12) (a) Enright, P. M.; O’Boyle, K. M.; Murphy, P. V. Org. Lett. 2000, 2, 3929. (b) Enright, P. M.; Tosin, M.; Nieuwenhuyzen, M.; Cronin, L.; Murphy, P. V. J. Org. Chem. 2002, 67, 3733. (13) The cyclic imine has been used in synthesis of 1. Paulsen, H.; Sangster, I.; Heyns, K. Chem. Ber. 1967, 100, 802. (14) Garegg, P. J.; Samuelsson, B. J. Chem. Soc., Perkin Trans. 1 1980, 2866. (15) The synthesis of 6-deoxyhex-5-enopyranosides by elimination of halogenated carbohydrates has been introduced. (a) Semeria, D.; Phillipe, M.; Delaumeny, J.-M.; Sepulchre, A.-M.; Gero, S. D. Synthesis 1983, 710. (b) Sakairi, N.; Kuzuhara, H. Tetrahedron Lett. 1982, 23, 5327. (c) Takeo, K.; Fukatsu, T.; Yasato, T. Carbohydr. Res. 1982, 107, 71. (d) Ferrier, R. J.; Prasit, P. Carbohydr. Res. 1980, 82, 263. (e) Sugawara, F.; Kuzuhara, H.; Agric. Biol. Chem. 1981, 45, 301. (f) Defaye, J.; Gadelle, A.; Wong, C. C. Carbohydr. Res. 1981, 94, 131. (16) A 1.4:1 mixture of epoxides was obtained. The major stereoisomer has been assigned the R configuration at C-5 on the basis of chemical shift and NOE data. (17) For the in situ generation of the fluorinated dioxirane, see: Yang, D.; Wong, M.-K.; Yip, Y.-C. J. Org. Chem. 1995, 60, 3887. Distilled dimethyldioxirane has been used provide epoxides from a similar alkene in good yields. See: Hartman, M. C. T.; Coward, J. K. J. Am. Chem. Soc. 2002, 124, 10036.
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SCHEME 2. Synthesis of 1 and 2
SCHEME 3
(determined by 1H NMR in CDCl3) placing the electronwithdrawing methoxy group in an axial orientation, fitting the anomeric effect, and the hydroxymethyl group in an equatorial orientation to minimize 1,3-diaxial interactions. Catalytic hydrogenation (40 psi) of 14, prepared by removal of acetates from 13, gave 1-deoxymannojirimycin 2 (23% for three steps) (Scheme 2). A sequence identical to that described for the synthesis of 2 did not, however, give 1 from 11b. Only 18 (Scheme 3) was obtained when the glucose-derived epoxide 11b was reacted with methanol. This is a result of nucleophilic attack at C-6 to give 16, which is followed by elimination of hydrogen azide to give 17 and further reaction with methanol. The acetylation of 18 gave the acyclic compound 19. The diverging behavior of 11a when compared to 11b can be explained by a stereoelectronic
effect. The reaction to give the product of methanol attack at C-5 is most likely to proceed via a carbocation/oxonium ion intermediate, and the rate will depend on the stability of this intermediate. Bols and co-workers18 have provided evidence that rates of hydrolysis of glycopyranosides are dependent on whether the substituents are axial or equatorial. They suggest that an electronegative group is more electron withdrawing when it is equatorial; positive charge formation at the anomeric center during the hydrolysis reaction is thus destabilized to a greater degree when there are more equatorial substituents. In the case of 11a, there are axial groups at C-1 and C-2 whereas for the glucose isomer 11b all substituents (from C-1 to C-4) have equatorial orientation. Also, the mannose isomer has the possibility of stabilization of positive charge formation at C-5 through participation by the axial 2-acyl group or through electrostatic interactions of axial groups. Presumably, carbocation/oxonium ion formation is therefore slower for 11b than for 11a and methanolysis proceeds for 11b via faster nucleophilic attack at C-6. The regioselectivity of the epoxide ring opening reaction of 11b was altered in the presence of camphorsulfonic acid, ensuring the efficient generation of the required carbocation/oxonium ion so that the desired ketal 12 was obtained. The acetate protecting groups were removed from 12, and subsequent catalytic hydrogenation at 500 psi gave 1.19 The overall isolated yields (over nine steps) were 4.4% for 1 and 10% for 2. The main reason for depletion of yields was the difficulty in purifying the final product by chromatography; in our hands, substantial losses were incurred. The analytical data for 1 and 2 (hydrochloride salt and amine) agreed with those of an authentic sample (Sigma) and with literature data.20 Synthesis of 1-Deoxygalactostatin and 1,6-Dideoxygalactostatin. The reactions of alkene 2021 with methyl(trifluoromethyl)dioxirane, generated in situ, and with buffered m-CPBA in dichloromethane did not give mixtures from which the expected epoxide(s) could be isolated; the epoxidation reactions were slow, and hydrolysis of the desired epoxide occurred. Epoxidation with m-CPBA in methanol as described by Catelani and coworkers22 gave the desired ketal derivatives 22 after acetylation in a low yield (26%). Deacetylation of 22 gave 23, and its subsequent hydrogenation at 500 psi gave 1-deoxygalactostatin as the major product in a mixture with the C-5 epimer 24 (ratio 4:1). The synthesis of 1,6dideoxygalactostatin was also achieved from 20; its reaction with NIS in methanol gave the iodo derivative 21, which was converted to 4 with high stereoselectivity (97:3)23 after deacetylation and catalytic hydrogenation. The analytical data for 3 and 4 were identical with authentic samples and with literature data.24 The iso(18) Bols, M.; Liang, X.; Jensen, H. H. J. Org. Chem. 2002, 67, 8970. (19) Catalytic hydrogenation at 40 psi did not give the desired product. (20) See ref 9s and: Fleet, G. W. J.; Ramsden, N. G.; Witty, D. R. Tetrahedron Lett. 1989, 30, 327. (21) Gyo¨rgydea´k, Z.; Szilagyi, L. Liebigs Ann. Chem. 1987, 235. (22) Catelani, G.; Corsaro, A.; D′Andrea, F.; Mariani, M.; Pistara` V.; Vittorino, E. Carbohydr. Res. 2003, 338, 2349. (23) The presence of 1,6-dideoxy-L-altronojirimycin in the product mixture was supported by the presence of a doublet at δ 1.31 in the 1H NMR. See ref 24b. (24) (a) Uriel C.; Santoyo-Gonza´lez, F.; Synlett 1999, 593. (b) Pistia, G.; Hollingsworth, R. I. Carbohydr. Res. 2000, 328, 467.
SCHEME 4
lated yields (seven steps) were 7% for 3 and 24 and 23.5% for 4. As for the synthesis of 1 and 2 there is room for further improvement, particularly in the route to 3 where epoxidation was a problem. 6-Deoxyhex-5-enopyranosyl azides have been used as intermediates for the synthesis of a range of iminosugars. The methodology may have future application in areas such as the synthesis of oligosaccharides that incorporate a terminal iminosugar residue or for medicinally interesting compounds based on iminosugar scaffolds.25 In addition the synthesis of the enantiomer of 4, 1-deoxyL-fuconojirimycin, which is a potent fucosidase inhibitor and relevant to the development of cell adhesion inhibitors,26 will be amenable from L-galactose which has been made available by chemical synthesis.27 Experimental Section 2,3,4,6-Tetra-O-acetyl-5-C-methoxy-β-D-glucopyranosyl Azide and 2,3,4,6-Tetra-O-acetyl-5-C-methoxy-r-L-idopyranosyl Azide 12. Epoxide mixture 11b (1.69 g, 4.5 mmol) was dissolved in MeOH (50 mL), and camphorsulfonic acid (0.51 g, 2.2 mmol) was added. This solution was stirred at room temperature under nitrogen for 10 min, diluted with CH2Cl2 (50 mL), washed with NaHCO3 (4 × 100 mL) and water (2 × 100 mL), and dried (MgSO4). The solvent was removed, and pyridine and acetic anhydride (1:1) were added to the residue. The mixture was stirred for 20 min, and the volatile components were then removed. Xylene (100 mL) was added and distilled from the residue in vacuo. The residue was purified by chromatography (EtOAc/petroleum ether (3:1) as eluant) to give the title compounds 12 (major isomer, 0.85 g, 48%; minor isomer 0.27 g, 15%). Analytical data for the major isomer: [R]D -51.8 (c 0.6, CHCl3); 1H NMR (300 MHz, CDCl3) δ 5.28 (apparent t, 1H, J ) 8.2), 5.18-5.22 (overlapping signals, 2H), 5.14 (d, 1H, J ) 8.4), 4.41 (d, 2H, J ) 12.5), 4.14 (d, 1H, J ) 12.5), 3.44 (s, 3H), 2.04, 2.08 (2s), 2.10 (each s, 12H); 13C NMR (125 MHz, CDCl3) δ 169.8, 169.7, 169.2, 168.6 (each s, each CdO), 100.3 (s, C-5), 85.6, 71.9, (25) Chery, F.; Murphy, P. V. Tetrahedron Lett. 2004, 45, 2067. (26) Simanek, E. E.; McGarvey, G. J.; Jablonski, J. A.; Wong, C.-H. Wong, Chem. Rev. 1998, 98, 833. (27) Kim, K. S.; Cho, B. H.; Shin, I. Bull. Kor. Chem. Soc. 2002, 23, 1193; Chem. Abstr. 2002, 138, 170409.
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71.0, 70.4 (each d), 60.0 (t, C-6), 49.6 (q, OMe), 20.5 (q, CH3); IR (KBr) 2900, 2111 (N3), 1754 (CdO), 1378, 1170, 1047 cm-1; CIHRMS found 421.1570, required 421.1571 (M + NH4)+. Analytical data for the minor isomer: [R]D -79.4 (c 0.33, CHCl3); 1H NMR (300 MHz, CDCl3) δ 5.50 (apparent t, 1H, J ) 9.5), 5.33 (d, 1H, J ) 9.5), 5.06 (apparent t, 1H, J ) 9.5), 4.79 (d, 1H, J ) 9.5), 4.30 (d, 1H, J ) 12.0), 4.22 (d, 1H, J ) 12.0), 3.45 (s, 3H), 2.13, 2.10, 2.08, 2.02 (each s, 12H); 13C NMR (125 MHz, CDCl3): δ 170.3, 170.0, 169.6, 169.5 (each s, each CdO), 99.1 (s, C-5), 83.5, 71.0, 69.9, 69.7 (each d), 61.6 (t, C-6), 49.7, (q, OMe), 20.8 (2s), 20.7, 20.75 (each q, each CH3); IR (KBr) 2963, 2120 (N3), 1754 (CdO), 1370, 1226, 1041; CI-HRMS found 421.1574, required 421.1571 (M + NH4)+. 1-Deoxynojirimycin 1. The isomers 12 (0.12 g, 0.3 mmol) were dissolved in MeOH (3 mL), a solution of sodium methoxide in MeOH (1 mL of 0.1 M) was added, and the mixture was stirred until the reaction was judged complete by TLC analysis. Amberlite IR-120 (H+) ion-exchange resin was added, and stirring was continued for 10 min. The residue (44 mg, 0.27 mmol) was dissolved in ethanol (50 mL) and stirred in a high-pressure reactor (Parr) under an atmosphere of hydrogen at 500 psi in the presence of Pd(OH)2 (20 mg) for 24 h. The mixture was filtered and the solvent removed. The residue was dissolved in MeOH (5 mL), and HCl (1 M in Et2O, 0.44 mL) was added. The solvent was evaporated and the residue chromatographed (eluting with MeOH-chloroform-triethylamine, 100:100:1), to give the title compound (11 mg, 19%). The NMR and other analytical data agreed with those previously reported21 and with those of an authentic sample (Sigma). 2,3,4,6-Tetra-O-acetyl-5-C-methoxy-r-L-altropyranosyl Azide and 2,3,4,6-Tetra-O-acetyl-5-C-methoxy-β-D-galactopyranosyl Azide 22. To 20 (0.50 g, 1.61 mmol) in dry MeOH (5 mL) and dry CH2Cl2 (5 mL) at 0 °C under a N2 atmosphere was slowly added a solution of m-CPBA (77% purity, 0.772 g, 3.22 mmol) in dry MeOH (5 mL), and the resulting mixture was allowed to warm to rt and stirred for 16 h. The mixture was then diluted with CH2Cl2 (50 mL), washed with aq NaHCO3 (4 × 50 mL), dried (MgSO4), and filtered, and solvent was removed in vacuo. The residue was stirred in acetic anhydride (5 mL), pyridine (5 mL), and DMAP (cat.) for 2 h. Water (10 mL) was added, and the product was extracted into EtOAc (3 × 10 mL). The combined organic portions were dried (MgSO4) and filtered, and solvent was removed in vacuo. Chromatography (6:1 petroleum ether-EtOAc) gave the title compounds (6:1, 0.168 g, 26%) as a yellow oil. Analytical data for the major isomer: Rf 0.48 (1:1 petroleum ether-EtOAc); [R]D -54.8 (c 0.5 CHCl3); 1H NMR (300 MHz, CDCl3) δ 5.42-5.46 (overlapping signals, 2H), 5.24 (apt t, 1H, J ) 10.4, 8.9 Hz), 4.73 (d, 1H, J ) 8.9 Hz), 4.29 (br s, 2H), 3.43 (s, 3H), 2.16, 2.13 2.12, 2.10 (each s, 12H); 13C NMR (125 MHz, CDCl3) δ 170.0, 169.9, 169.6, 169.6 (each s, each Cd O), 100.6 (s, C-5), 74.1 (d, C-1), 68.7, 68.1, 67.6 (each d, C-2_4), 57.8 (t, C-6), 49.1 (q, OCH3), 20.8, 20.7 (each q, each CH3); CIHRMS found 421.1574 required 421.1571 [M + NH4]+. Analytical data for the minor isomer: Rf 0.45 (1:1 petroleum etherEtOAc); [R]D -17.2 (c 0.5 CHCl3); 1H NMR (300 MHz, CDCl3) δ 5.53 (d, 1H, J ) 3.8 Hz), 5.33 (dd, 1H, J ) 8.0, 3.8 Hz), 5.26 (dd, 1H, J ) 8.0, 5.0 Hz), 5.13 (d, 1H, J ) 5.0 Hz), 4.39 (d, 1H, J ) 12.2 Hz), 4.33 (d, 1H, J ) 12.2 Hz), 3.53 (s, 3H, OCH3), 2.21, 2.17, 2.10 (each s, 12H); 13C NMR (125 MHz, CDCl3) δ 170.3, 170.1, 170.1, 169.6 (each s, each CdO), 98.5 (s, C-5), 87.0 (d, C-1), 69.8, 67.8, 67.3, (each d, C-2_4), 62.0 (t, C-6), 50.6 (q, OCH3), 20.9, 20.8 (each q, each CH3); IR (film) ν 2964, 2114 (N3), 1746 (CdO), 1372, 1226, 1042 cm-1; CI-HRMS found 421.1573, required 421.1571 [M + NH4]+. 1-D-Deoxygalactostatin 3. A solution of the major isomer of 22 (60 mg, 0.15 mmol) was stirred in MeOH containing sodium methoxide (0.1 M, 5 mL) for 2 h. Solid CO2 was then added, and the solvent was removed in vacuo. Chromatography (6:1 CH2Cl2-EtOH) gave 23 as a yellow oil (30 mg, 86%): Rf 0.84 (3:2 EtOAc-MeOH); [R]D -62.4 (c 0.5 MeOH); 1H NMR (D2O, 300 MHz) δ 4.74 (d, overlapping with HOD, 1H), 3.86 (dd, 1H, J ) 10.8, 3.4 Hz), 3.86 (d, 1H, J ) 3.4 Hz), 3.72 (d, 1H, J ) 12.3 Hz, H-6), 3.66 (d, 1H, J ) 12.3 Hz), 3.48 (apparent t, 1H, J ) 10.8 Hz), 3.31 (s, 3H, OCH3); 13C NMR (D2O, 300 MHz) δ 102.3 (s,
3568 J. Org. Chem., Vol. 69, No. 10, 2004
C-5), 86.5 (d, C-1), 69.9, 69.7, 68.5 (each d, C-2_4), 56.6 (t, C-6), 48.2 (q, OCH3); CI-HRMS found 253.1148, required 253.1148 [M + NH4]+. The azide 23 (22 mg, 0.094 mmol) was dissolved in EtOH (40 mL) and was stirred for 2 days under an atmosphere of hydrogen at a pressure of 500 psi in the presence of palladium hydroxide (22 mg). The reaction mixture was filtered through Celite, and the solvent was removed in vacuo. Chromatography (1:1 CHCl3-MeOH and 1% aq NH3) gave, as an inseparable mixture, the title compound and 1-L-deoxyaltronojirimycin 24 (ratio 3/24 ) 4:1, 10.5 mg, 70%). The NMR data for 3 and 24 were in agreement with those reported previously.24a 6-Deoxy-6-iodo-5-C-methoxy-β-D-galactopyranosyl Azide 21. To 20 (0.5 g, 1.6 mmol) stirring in dry MeOH (5 mL) under a N2 atmosphere was added NIS (1.08 g, 4.8 mmol) dissolved in dry MeOH (5 mL). The reaction was stirred for 2 h, diluted with CH2Cl2 (50 mL), washed with 10% sodium thiosulfate solution (2 × 50 mL) and aq NaHCO3 solution (50 mL), dried (MgSO4), and filtered and the solvent removed in vacuo. Chromatography (4:1 petroleum ether-EtOAc) gave 2,3,4-tri-O-acetyl-6-deoxy-6iodo-5-C-methoxy-β-D-galactopyranosyl and 2,3,4-tri-O-acetyl-6deoxy-6-iodo-5-C-methoxy-R-L-altropyranosyl azide (galactose isomer, 0.52 g, 69%; altrose isomer, 0.11 g, 15%). Analytical data for the galactose isomer; Rf 0.55 (1:1 petroleum ether-EtOAc): [R]D -5.9 (c 0.4 CHCl3); 1H NMR (300 MHz, CDCl3) δ 5.50 (d, 1H, J ) 3.4 Hz), 5.33 (dd, 1H, J ) 10.4, 3.4 Hz), 5.09 (apparent t, 1H, J ) 8.9 Hz), 4.61 (d, 1H, J ) 8.9 Hz), 3.28 (overlapping signals, 5H), 2.11, 2.01, 1.91 (each s, 9H, each CH3); 13C NMR (125 MHz, CDCl3) δ 169.8, 169.6, 169.2 (each s, each CdO), 100.7 (s, C-5), 84.9, 69.4, 68.9, 67.7 (each d, C-1-4), 48.3 (q, OCH3), 20.9, 20.8, 20.7 (each q, each CH3), 0.2 (t, C-6); IR (film) υ 2985, 2118 (N3), 1753 (CdO), 1370, 1218 cm-1; CI-HRMS found 489.0486, required 489.0485 [M + NH4]+. Analytical data for the altrose isomer: Rf 0.53 (1:1 petroleum ether-EtOAc); [R]D -11.4 (c 0.4 CHCl3); 1H NMR (300 MHz, CDCl3) δ 5.69 (d, 1H, J ) 3.4 Hz), 5.20-5.23 (overlapping signals, 2H), 4.95 (d, 1H, J ) 6.4 Hz), 3.56 (d, 1H, J ) 11.9 Hz), 3.49 (s, 3H), 3.45 (d, 1H, J ) 11.9 Hz), 2.19, 2.13, 2.07 (each s, 9H); 13C NMR (125 MHz, CDCl3) δ 170.0, 169.8, 169.4 (each s, each CdO), 97.8 (s, C-5), 85.9 (C-1), 69.1, 68.7, 68.0 (each d, C-2-4), 50.3 (q, OCH3), 20.8, 20.8, 20.7 (each q, each CH3), 3.3 (t, C-6); IR (film) ν 2986, 2115 (N3), 1753 (CdO), 1641, 1371, 1220, 1021 cm-1; CI-HRMS found 489.0483, required 489.0482 [M + NH4]+. Deacetylation of the galactose isomer (0.36 g, 0.77 mmol) as described for 22 and purification of the residue by chromatography (6:1 CH2Cl2EtOH as eluant) gave 21 as a yellow oil (0.168 g, 93%): Rf 0.22 (3:2 CH2Cl2-EtOAc); [R]D -2.2 (c 0.6 MeOH); 1H NMR (D2O, 300 MHz) δ 4.72 (d, 1H, J ) 8.8 Hz), 4.08 (d, 1H, J ) 3.4 Hz), 3.82 (dd, 1H, J ) 10.0, 3.4 Hz), 3.47-3.53 (overlapping signals, 3H), 3.31 (s, 3H); 13C NMR (D2O, 300 MHz) δ 100.2 (s, C-5), 86.0 (d, C-1), 68.7, 68.5, 68.3 (each d, C-2_4), 46.8 (q, OCH3), 1.1 (t, C-6); IR (film) ν 3421 (O-H), 1363, 1220, 1027 cm-1; CI-HRMS found 363.0165, required 363.0166 [M + NH4]+. 1,6-Dideoxy-D-galactostatin 4. A solution of 21 (26 mg, 0.075 mmol), in EtOH (40 mL) was stirred for 2 days under a hydrogen atmosphere at 500 psi in the presence of palladium hydroxide (26 mg). The reaction was filtered through Celite, IR67 (weakly basic) ion-exchange resin was added, the solution was stirred for 10 min and filtered, and the solvent was removed in vacuo. Chromatography (3:1 CH2Cl2-MeOH) gave the title compound 4 (8 mg, 73%). The analytical data were agreement with those of an authentic sample (Sigma) and with data in the literature.24b
Acknowledgment. We thank Pfizer Pharmaceuticals Ltd. Ringaskiddy, Co. Cork ,and Enterprise Ireland for funding (SC/2002/0225). Supporting Information Available: Experimental procedures and analytical data for all other compounds and 1H and 13C spectra. This material is available free of charge via the Internet at http://pubs.acs.org. JO035763U
