4226
C. Yamada et al. / Tetrahedron Letters 48 (2007) 4223–4227
Takeuchi, K.; Mukaiyama, T. Bull. Chem. Soc. Jpn. 2002,
75, 291.
using a nonvolatile ionic liquid and the reusability of the
ionic liquid without any loss in efficiency were also dem-
onstrated as notable features of this aryl C-glycosylation
reaction.
8. For pioneering works on O- to C-glycosidic rearrange-
ment in aryl C-glycosylation reactions, see: (a) Matsu-
moto, T.; Katsuki, M.; Suzuki, K. Tetrahedron Lett. 1988,
29, 6935; (b) Kometani, T.; Kondo, H.; Fujimori, Y.
Synthesis 1988, 1005.
9. Itoh and his co-workers have elegantly demonstrated an
enzymatic acylation under reduced pressure conditions in
an ionic liquid solvent to remove volatile co-products from
the reaction mixture. See: Itoh, T.; Akasaki, E.; Nishi-
mura, Y. Chem. Lett. 2002, 31, 154.
10. Aryl C-glycosylation using unprotected sugars, see: (a)
Toshima, K.; Matsuo, G.; Ishizuka, T.; Nakata, M.;
Kinoshita, M. J. Chem. Soc., Chem. Commun. 1992, 1641;
(b) Toshima, K.; Matsuo, G.; Nakata, M. J. Chem. Soc.,
Chem. Commun. 1994, 997; (c) Matsuo, G.; Matsumura,
S.; Toshima, K. Chem. Commun. 1996, 2173; (d) Toshima,
K.; Ushiki, Y.; Matsuo, G.; Matsumura, S. Tetrahedron
Lett. 1997, 56, 841; (e) Toshima, K.; Matsuo, G.; Ishizuka,
T.; Ushiki, Y.; Nakata, M.; Matsumura, S. J. Org. Chem.
1998, 63, 2307.
Acknowledgements
This research was supported in part by a Grant-in-Aid
for the 21st Century COE Program ‘KEIO Life Conju-
gated Chemistry’, for Scientific Research on Priority
Areas 18032068, and for JSPS Fellows 18Æ6013 from
the Ministry of Education, Culture, Sports, Science,
and Technology, Japan.
References and notes
1. For some reviews of ionic liquids, see: (a) Welton, T.
Chem. Rev. 1999, 99, 2071; (b) Wasserscheid, P.; Keim, W.
Angew. Chem., Int. Ed. 2000, 39, 3772; (c) Scheldon, R.
Chem. Commun. 2001, 2399; (d) Baudequin, C.; Baudoux,
J.; Levillain, J.; Cahard, D.; Gaumont, A.-C.; Plaquevent,
J.-C. Tetrahedron: Asymmetry 2003, 14, 3081; (e) Jain, N.;
Kumar, A.; Chauhan, S.; Chauhan, S. M. S. Tetrahedron
2005, 61, 1015; (f) Baudequin, C.; Baudoux, J.; Levillain,
J.; Guillen, F.; Plaquevent, J.-C.; Gaumont, A.-C. Tetra-
hedron: Asymmetry 2005, 16, 3921; (g) Muzart, J. Adv.
Synth. Catal. 2006, 348, 275.
11. The effect of interaction of the glycosyl oxonium cation
intermediate with the anion moiety of the ionic liquid on
the stereoselectivity of glycosylation has been reported.
See Refs. 3g,h and 6b.
12. The typical procedure for the aryl C-glycosylation of 2 and
5 under reduced pressure: To a mixture of 2 (0.1 mmol)
and 5 (0.2 mmol) was added acid-ionic liquid, HBF4
(1.0 mol % to IL)/C6mim[BF4] (0.1 M for 2), which was
prepared by addition of HBF4 (ether solution) to
C6mim[BF4] followed by drying at 70 ꢁC under reduce
pressure (2 mmHg) for 3 h. After stirring at 60 ꢁC under
reduced pressure (2 mmHg) for 1 h, the mixture was
extracted with 3:1 hexane–ethyl acetate several times. The
extracts were combined and then concentrated in vacuo.
Purification of the residue by flash column chromatogra-
phy (SiO2, hexane–ethyl acetate = 2/1) gave aryl b-C-
glycoside 7 in 82% yield.
2. Ionic Liquids in Synthesis; Wasserscheid, P., Welton, T.,
Eds.; Wiley-VCH: Weinheim, 2002.
3. For glycosylations in ionic liquid, see: (a) Yadav, J. S.;
Reddy, B. V. S.; Reddy, J. S. S. J. Chem. Soc., Perkin
Trans. 1 2002, 2390; (b) Pakulski, Z. Synthesis 2003, 2074;
(c) Poletti, L.; Rencurosi, A.; Lay, L.; Russo, G. Synlett
2003, 2297; (d) Tilve, R. D.; Alexander, M. V.; Khandkar,
A. C.; Samant, S. D.; Kanetkar, V. R. J. Mol. Catal. A:
Chem. 2004, 223, 237; (e) Anjaiah, S.; Chandrasekhar, S.;
13. All aryl C-glycosides were purified by silica-gel chroma-
tography and were characterized by spectroscopic means.
The anomeric configuration is assigned in each case with
the aid of 1H NMR analysis and/or confirmed by the
comparison with the authentic samples. See, Refs. 5a,b
´
Gree, R. J. Mol. Catal. A: Chem. 2004, 214, 133; (f) Naik,
P. U.; Nara, S. J.; Harjani, J. R.; Salunkhe, M. M. J. Mol.
Catal. A: Chem. 2005, 234, 35; (g) Rencurosi, A.; Lay, L.;
Russo, G.; Caneva, E.; Poletti, L. J. Org. Chem. 2005, 70,
7765; (h) Rencurosi, A.; Lay, L.; Russo, G.; Caneva, E.;
Poletti, L. Carbohydr. Res. 2006, 341, 903.
1
and 10e. H NMR (300 MHz) spectra (d, SiMe4; J = Hz)
of new aryl C-glycosides 8, 9, and 15 are the following.
Compound 8: 1H NMR (CDCl3, TMS): d 8.32 (1H, s,
OH), 7.40–7.16 (15H, m, ArH), 6.28 (1H, s, H-4), 4.94
4. For a recent review of aryl C-glycosides, see: Bililign, T.;
Griffith, B. R.; Thorson, J. S. Nat. Prod. Rep. 2005, 22,
742.
(1H, dd, J2 ax;1 ¼ 11:7, J2 eq;1 ¼ 2:1, H-10), 4.94 and 4.54
(2H, ABq, J = 11.1, ArCH2), 4.71 and 4.64 (2H, ABq,
J = 11.7, ArCH2), 4.60 and 4.46 (2H, ABq, J = 12.0,
ArCH2), 3.87, 3.83, and 3.77 (each 3H, s, OMe), 3.84–3.75
0
0
0
0
5. For recent aryl C-glycosylations, see: (a) Palmacci, E. R.;
Seeberger, P. H. Org. Lett. 2001, 3, 1547; (b) Plante, O. J.;
Palmacci, E. R.; Andre, R. B.; Seeberger, P. H. J. Am.
Chem. Soc. 2001, 123, 9545; (c) Ben, A.; Yamauchi, T.;
Matsumoto, T.; Suzuki, K. Synlett 2004, 225; (d) Yama-
uchi, T.; Watanabe, Y.; Suzuki, K.; Matsumoto, T.
Synthesis 2006, 2818; (e) Li, Y.; Wei, G.; Yu, B.
Carbohydr. Res. 2006, 341, 2717.
6. (a) Sasaki, K.; Nagai, H.; Matsumura, S.; Toshima, K.
Tetrahedron Lett. 2003, 44, 5605; (b) Sasaki, K.;
Matsumura, S.; Toshima, K. Tetrahedron Lett. 2004, 45,
7043.
7. For activation of glycosyl fluorides by protic acids, see: (a)
Toshima, K.; Kasumi, K.; Matsumura, S. Synlett 1998,
643; (b) Toshima, K.; Kasumi, K.; Matsumura, S. Synlett
1999, 813; (c) Toshima, K.; Nagai, H.; Kasumi, K.;
Kawahara, K.; Matsumura, S. Tetrahedron 2004, 60, 5331;
(d) Jona, H.; Mandai, H.; Mukaiyama, T. Chem. Lett.
2001, 426; (e) Jona, H.; Mandai, H.; Chavasiri, W.;
(3H, m, H-60, H-40, H-30), 3.67 (1H, dd, J6 ;6 ¼ 10:2,
0
0
J6 ;5 ¼ 2:1, H-60), 3.58–3.51 (1H, m, H-50), 2.29 (1H, ddd,
0
0
J3 ;2 eq ¼ 4:5, J2 ax;2 eq ¼ 11:1, J2 eq;1 ¼ 2:1, H-20eq), 1.89
0
0
0
0
0
0
(1H, ddd, J3 ;2 ax ¼ J2 ax;2 eq ¼ 11:1, J2 ax;1 ¼ 11:7, H-20ax).
Compound 9: 1H NMR (CDCl3, TMS): d 8.14 (1H, s,
OH), 7.38–7.27 (10H, m, ArH), 6.24 (1H, s, H-4), 5.01 and
0
0
0
0
0
0
0
0
4.70 (2H, ABq, J = 11.1, ArCH2), 4.89 (1H, dd, J2 ax;1
¼
11:7, J2 eq;1 ¼ 2:1, H-10), 4.70 and 4.62 (2H, ABq,
J = 11.7, ArCH2), 3.87, 3.81, and 3.77 (each 3H, s,
OMe), 3.84–3.74 (1H, m, H-30), 3.54 (1H, dq,
0
0
J6 ;5 ¼ 6:0, J5 ;4 ¼ 9:0, H-50), 3.23 (1H, dd,J5 ;4
¼
0
0
0
0
0
0
J4 ;3 ¼ 9:0, H-40), 2.31 (1H, ddd, J3 ;2 eq ¼ 5:1,
0
0
0
0
J2 ax;2 eq ¼ 13:2, J2 eq;1 ¼ 2:1, H-20eq), 1.87 (1H, ddd,
0
0
0
0
J3 ;2 ax ¼ 11:4, J2 ax;2 eq ¼ 13:2, J2 ax;1 ¼ 11:7, H-20ax),
0
0
0
0
0
0
1
1.39 (3H, d, J6 ;5 ¼ 6:0, H-60). Compound 15: H NMR
(acetone-d6, TMS): d 8.80 (1H, s, ArOH), 7.82 (1H, dd,
J8,7 = 7.8, J8,6 = 2.7, H-8), 7.82–7.76 (1H, m, ArH), 7.63–
0
0