Gold-catalyzed glycosidations: Synthesis of 1,6-anhydro saccharides

Article abstract of DOI:10.1016/j.tetlet.2010.09.004

Various 1,6-anhydro sugars are synthesized utilizing salient features of gold-catalyzed glycosidations. All the reactions occurred under mild conditions in the presence of 7 mol % of AuBr₃ enabling easy synthesis of 1,6-anhydro sugars from corr

Full text of DOI:10.1016/j.tetlet.2010.09.004

Tetrahedron Letters 51 (2010) 5912–5914
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Tetrahedron Letters
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Gold-catalyzed glycosidations: synthesis of 1,6-anhydro saccharides
⇑
Shivaji A. Thadke, Srinivas Hotha
Division of Organic Chemistry, Combi Chem – BioResource Center, National Chemical Laboratory (CSIR), Dr. Homi Bhabha Road, Pune 411 008, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Various 1,6-anhydro sugars are synthesized utilizing salient features of gold-catalyzed glycosidations. All
the reactions occurred under mild conditions in the presence of 7 mol % of AuBr3 enabling easy synthesis
of 1,6-anhydro sugars from corresponding 6-hydroxy propargyl/methyl monosaccharides, disaccharides,
and trisaccharides in good yields.
Received 18 August 2010
Revised 1 September 2010
Accepted 2 September 2010
Available online 8 September 2010
Ó 2010 Elsevier Ltd. All rights reserved.
1,6-Anhydro sugars are excellent synthons for the syntheses of
medicinally important molecules1 and materials.2 They are also
known to be precursors for the synthesis of proteoglycans, glycosyl
halides,3a N- or S-glycosides,3b–d and C-glycosides.3e,f Stereoregular
or hyperbranched glycopolymers are also reported from 1,6-anhy-
dro sugars by cationic ring-opening polymerization.4 Interesting
opportunities for the synthesis of complex molecules and novel
glycopolymers prompted the development of methods for the syn-
thesis of this set of sugar derivatives.5
1,6-Anhydro sugar derivatives are synthesized either by thermal
degradation or alternatively by chemical reactions.5 Thermal degra-
dation or pyrolysis exploited all the major conventional and non-
conventional reaction media as well as the convection sources to
get 1,6-anhydro sugars.5b–f The major limitation of a thermal degra-
dation process is that they are more suitable to 1,6-anhydro mono-
saccharides and really tough to limit pyrolysis for 1,6-anhydro
oligosaccharides.5a However, 1,6-anhydro sugar derivatives by
chemical reactions enjoy the control and selective synthesis which
are otherwise not easy.1b An usual sequence for the chemical syn-
thesis of 1,6-anhydro sugars involves a leaving group at the anomer-
ic position with the 6-hydroxyl group and the remaining hydroxyl
groups are protected. Till date, Shoda’s direct synthesis of 1,6-anhy-
dro saccharides from unprotected glycopyranosides by the use of
2-chloro-1,3-dimethylimidazolinium chloride is the best.5a In
summary, most of the reported methods use stoichiometric quanti-
ties of reagents, often long reaction times, and tedious isolation
procedures. Thus methods that enable the synthesis of 1,6-anhydro
sugar derivatives through catalytic means are needed.1b
Lewis as well as the Brønsted acidity of Au(III) salts.6 Usually, a
glycosylation reaction involves a fully protected glycosyl donor
with a leaving group at the anomeric position and a glycosyl accep-
tor (aglycone) that frequently contains a single hydroxyl moiety
and the reaction happens in an intermolecular fashion.7
Thus we hypothesized that if the glycosylation is carried out
intramolecularly on a sugar substrate containing a 6-OH group
(other hydroxyl groups being protected) and a leaving group at
the C-1 position, the reaction shall proceed to yield 1,6-anhydro
sugars. This proposition was further fueled by a recent observation
that showed cleavage of the interglycosidic bond and formation of
1,6-anhydro mannoside (4) and disaccharide 3 from an armed
disaccharide (1) and aglycone 2 under gold-catalyzed glycosidation
conditions (Scheme 1).8
Accordingly, an acetonitrile solution of propargyl 2,3,4-tri-O-
benzyl mannopyranoside 5a was heated to 70 °C for 10 h to isolate
1,6-anhydro mannoside 4 in 71% yield after concentration in vacuo
followed by filter column chromatographic purification.9–11 In an-
other reaction, methyl mannopyranoside (5b) was also found to
give compound 4 in 62% yield when subjected to above delineated
reaction conditions (Scheme 2).10
Aforementioned results enticed us to evaluate the general
applicability of the current protocol for the synthesis of other
1,6-anhydro sugars of monosaccharides, disaccharides, and trisac-
charides. 1,6-Anhydro sugar formation was then checked with
gluco-(6a,6b) and galacto-(7a,7b) substrates as well to obtain the
corresponding 1,6-anhydro derivatives 8 and 9 in good yields
(Table 1).9 In addition, the suitability of 1,6-anhydro sugar forma-
tion has been studied with a panel of disaccharides and trisaccha-
rides. Interesting to note that AuBr3-catalyzed intramolecular
reaction occurred on disaccharides (10a, 10b, 11a, and 11b) and
trisaccharides (14a, 14b, 15a, and 15b) resulting in the formation
of the corresponding 1,6-anhydro sugar derivatives (12, 13, 16,
and 17) in good yields.9 It is pertinent to mention that the inherent
acidity in the Au(III)-catalyzed glycosidation showed the domino
effect in one-pot. Deprotection of 6-O-silyl ether happened first
to give the 6-OH compound that got subsequently converted to
The foregoing discussion encouraged us to ponder upon devel-
oping a catalytic route to the synthesis of 1,6-anhydro saccharides
taking the cue from recent observations in gold-catalyzed glycosi-
dations. In our laboratory, we have identified propargyl and methyl
glycosides as novel glycosyl donors taking advantage of both the
⇑
Corresponding author. Tel.: +91 20 2590 2401; fax: +91 20 2590 2624.
E-mail address: s.hotha@ncl.res.in (S. Hotha).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.09.004

S. A. Thadke, S. Hotha / Tetrahedron Letters 51 (2010) 5912–5914
5913
OBn
OBn
OBn
OBn
OH
O
O
O
BnO
BnO
BnO
OBn
O
OBz
BnO
O
OBn
BzO
O
O
AuBr3, CH3CN
70oC, 8h
BzO
+
+
OBn
OBn
O
OBz
O
O
BzO
BzO
BnO
BnO
2
4 (20%)
Disarmed
O
O
1
Armed
3 (53%)
Scheme 1. Cleavage of interglycosidic bond and formation of 1,6-anhydro mannoside.
1,6-anhydro sugar via the intramolecular trapping of the oxocarbe-
nium ion generated due to the extrusion of the anomeric alkyl
(propargyl/methyl) group by the action of AuBr3.
In conclusion, the synthesis of 1,6-anhydro sugars from the cor-
responding 6-hydroxy propargyl/methyl glycosides was realized in
the presence of a catalytic amount of AuBr3 at 70 °C in acetonitrile.
Interestingly, deprotection of 6-O-TBDPS ether was observed for
the first time in the presence of catalytic quantity of AuBr3 and
subsequent intramolecular glycosidation happened in domino
OH
OBn
O
OBn
O
O
7mol% AuBr3
BnO
BnO
OBn
CH3CN
OBn
70 oC, 10h
4
O
R
71% from 5a, 62% from 5b
5a R =
, 5b R = CH3
Scheme 2. AuBr3 catalyzed synthesis of 1,6-anhydro mannoside from propargyl
and methyl mannopyranosides.
Table 1
Synthesis of 1,6-anhydro saccharides
Substrate
Product
Time, Yield
R =
R = CH3
OH
O
OBn
O
O
BnO
BnO
4 h, 75%
24 h, 69%
OBn OBn
BnO
O
R
8
6a R =
, 6b R = CH3
OH
O
BnO
OBn
O
BnO
O
BnO
12 h, 76%
18 h, 65%
OBn
BnO
O
R
9
7a R =
, 7b R = CH3
OTBDPS
O
OBn
O
O
BnO
BnO
BzO
OBn
O
BzO
O
18 h, 71%
20 h, 64%
O
O
O
,
BzO
BzO
R
BzO
BzO
OBz
OBz
12
10a
10b
R =
R = CH3
OBz
O
OTBDPS
O
OBn
OBz
O
O
BzO
O
BzO
O
BzO
BzO
BnO
20 h, 72%
24 h, 68%
O
OBn
BzO
BnO
O
OBz
13
R
11a R =
, 11b R = CH3
OTBDPS
O
OBn
O
O
OBz
BnO
BnO
OBz
BzO
BzO
BzO
BzO
BzO
OBn
O
O
BzO
O
20 h, 67%
18 h, 64%
O
O
O
O
O
O
R
BzO
BzO
OBz
OBz
OBz
OBz
14a R
14b R
=
,
=
CH3
16
OBz
O
OBz
OTBDPS
O
BzO
OBn
O
OBz
OBz
BzO
BzO
O
O
O
O
O
BzO
O
BzO
O
BnO
OBn
10 h, 65%
18 h, 62%
O
OBz
BzO
OBz
BnO
O
OBz
OBz
R
17
15a R =
,15b R = CH3

5914
S. A. Thadke, S. Hotha / Tetrahedron Letters 51 (2010) 5912–5914
7. (a) Zhu, X.; Schmidt, R. R. Angew. Chem., Int. Ed. 2009, 48, 1900–1934; (b)
Paulsen, H. Angew. Chem., Int. Ed. Engl. 1982, 21, 155–173; (c) Fraser-Reid, B.;
Udodong, U. E.; Wu, Z.; Ottosson, H.; Merritt, J. R.; Rao, C. S.; Roberts, C.;
Madsen, R. Synlett 1992, 927–942.
fashion to give 1,6-anhydro sugar derivatives of disaccharides and
trisaccharides.
8. Kayastha, A. K.; Hotha, S. Tetrahedron Lett. 2010, 51, 5269–5272.
9. All products gave satisfactory 1H, 13C, DEPT NMR and MS analysis. See
Supplementary data.
Acknowledgments
S.H. thanks the financial support from CSIR (NWP0036-B) and
Director NCL for LC–MS facility. S.A.T. acknowledges the fellowship
from CSIR, New Delhi.
10. General procedure for the synthesis of 1,6-anhydro sugars: To a solution of 6-
hydroxy alkyl glycopyranoside (0.1 mmol) in anhydrous acetonitrile (2 mL)
was added 7 mol % of AuBr3 under argon atmosphere at room temperature. The
resulting mixture was heated to 70 °C and stirred till the completion of the
reaction as judged by TLC analysis (Table 1). The reaction mixture was
concentrated in vacuo to obtain a crude residue which was purified by silica gel
column chromatography using ethyl acetate–petroleum ether (1:4) as mobile
phase.
Supplementary data
11. (a) Compound characterization data for compound 4: ½a D25
(CHCl3, c 1.0) ꢁ16.6;
ꢀ
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2010.09.004.
1H NMR (200.13 MHz, CDCl3): d 3.47(t, 1H, J = 1.8 Hz), 3.58(dd, 1H, J = 1.8,
5.4 Hz), 3.73(dd, 1H, J = 6.0, 7.1 Hz), 3.81(qd, 1H, J = 1.6, 3.1, 5.0 Hz), 4.25(dd,
1H, J = 0.9, 7.1 Hz), 4.43–4.57(m, 5H), 4.52(ABq, 2H, J = 12.4 Hz), 5.46(s, 1H),
7.20–7.38(m, 15H); 13C NMR (50.32 MHz, CDCl3): d 65.0, 71.3, 71.4, 73.4, 74.1,
74.4, 74.5, 76.5, 100.1, 127.7–128.5, 137.6, 137.9, 137.9; HRMS (MALDI-TOF)
Calcd for C27H28O5Na: 455.1834; Found, 455.1830.
References and notes
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Wang, C.-C.; Chang, S.-W.; Chen, C.-S. Tetrahedron Lett. 2001, 42, 1321–1324;
(d) Hung, S.-C.; Puranik, R.; Chi, F.-C. Tetrahedron Lett. 2000, 41, 77–80; (e)
Takeuchi, M.; Taniguchi, T.; Ogasawara, K. Tetrahedron Lett. 2000, 41, 2609–
2611; (f) Witczak, Z. J. Pure Appl. Chem. 1994, 66, 2189–2192; (g) Georges, M.;
MacKay, D.; Fraser-Reid, B. J. Am. Chem. Soc. 1982, 104, 1101–1103; (h)
Kochetkov, N. K.; Sviridov, A. F.; Ermolenko, M. S. Tetrahedron Lett. 1981, 22,
4315–4322; (i) Kochetkov, N. K.; Sviridov, A. F.; Ermolenko, M. S. Tetrahedron
Lett. 1981, 22, 4319–4322; (j) Kelly, A. G.; Roberts, J. S. J. Chem. Soc., Chem.
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1977, 57, C31–C35.
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Ishii, F.; Kakuchi, T. Macromolecules 2005, 38, 4202–4210; (c) Ohara, M.;
Takagaki, A.; Nishimura, S.; Kohki, E. Appl. Catal., A Gen. 2010, 383, 149–155.
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Hinou, H.; Nishimura, S. Angew. Chem., Int. Ed. 2007, 46, 3074–3079; (b)
Nambia, S.; Daeuble, J. F.; Doyle, R. J.; Taylor, K. G. Tetrahedron Lett. 1989, 30,
2179–2182; (c) Arndt, S.; Hsieh-Wilson, L. C. Org. Lett. 2003, 4179–4182; (d)
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118, 3818–3828; (f) Stichler-Bonaparte, J.; Vasella, A. Helv. Chem. Acta 2001, 84,
2355–2367.
(b) Compound characterization data for compound 8: ½a D25
(CHCl3, c 1.0) ꢁ26.0;
ꢀ
1H NMR (200.13 MHz, CDCl3): d 3.34(d, 2H, J = 1.7 Hz), 3.58(quintet, 1H, J = 2.4,
3.6 Hz), 3.67(dd, 1H, J = 5.9, 7.2 Hz), 5.91(dd, 1H, J = 0.8, 7.2 Hz), 4.41(ABq, 2H,
J = 12.5 Hz), 4.48–4.63(m, 5H), 5.46(s, 1H), 7.21–7.35(m, 15H); 13C NMR
(50.32 MHz, CDCl3): d 65.3, 71.1, 71.7, 71.9, 74.2, 75.8, 75.9, 76.6, 100.5,
127.5–128.4, 137.7, 137.8, 137.8; HRMS (MALDI-TOF) Calcd for C27H28O5Na,
455.1834; Found, 455.1840.
(c) Compound characterization data for compound 9: ½a D25
(CHCl3, c 1.2) ꢁ34.9;
ꢀ
1H NMR (200.13 MHz, CDCl3): d 3.52(t, 1H, J = 1.7 Hz), 3.62(t, 1H, J = 6.0 Hz),
3.77–3.92(m, 2H), 4.35–4.66(m, 8H), 5.36(t, 1H, J = 1.7 Hz), 7.22–7.37(m, 15H);
13C NMR (50.32 MHz, CDCl3): d 64.3, 71.1, 72.1, 72.7, 73.0, 73.1, 74.1, 76.3,
100.2, 127.6–128.5, 137.5, 137.9, 138.2; HRMS (MALDI-TOF) Calcd for
C
27H28O5Na, 455.1834; Found, 455.1836.
(d) Compound characterization data for compound 12: ½a D25
ꢀ
(CHCl3, c 1.1)
+16.2; 1H NMR (200.13 MHz, CDCl3): d 3.07(s, 1H), 3.42(s, 1H), 3.49(dd, 1H,
J = 5.9, 7.3 Hz), 3.77(dd, 1H, J = 0.8, 7.3 Hz), 3.88(m, 1H), 4.31–4.57(m, 7H),
4.62(ABq, 2H, J = 12.4 Hz), 5.21(s, 1H), 5.38(dd, 1H, J = 8.0, 9.6 Hz), 5.58(t, 1H,
J = 9.8 Hz), 5.75(t, 1H, J = 9.8 Hz), 7.20–7.76(m, 22H), 7.77–8.09(m, 8H); 13C
NMR (100.61 MHz, CDCl3): d 62.8, 64.8, 69.5, 71.2, 71.4, 72.2, 72.2, 72.5, 74.2,
75.2, 75.7, 76.0, 99.8, 100.2, 127.6–129.9, 133.2, 133.3, 133.3, 133.5, 137.7,
137.9, 164.9, 165.2, 165.7, 166.0; HRMS (MALDI-TOF) Calcd for C54H48O14Na,
943.2942; Found, 943.2949.
(e) Compound characterization data for compound 13: ½a D25
ꢀ
(CHCl3, c 0.9)
4. (a) Satoh, T.; Imai, T.; Kitajyo, Y.; Kakuchi, T. Curr. Top. Polym. Res. 2005, 195–
231; (b) Varma, A. J.; Kennedy, J. F.; Galgali, P. Carbohydr. Polym. 2004, 56, 429–
445; (c) Mori, M.; Kusuno, A.; Satoh, T.; Kaga, H.; Miura, M.; Tsuda, K.; Kakuchi,
T. Polym. Preprints 2002, 43, 547–548.
ꢁ13.4; 1H NMR (500.13 MHz, CDCl3): d 3.27(s, 1H), 3.55(dd, 1H, J = 6.2, 7.2 Hz),
3.65(s, 1H), 3.80(s, 1H), 3.84(d, 1H, J = 7.3 Hz), 4.10(m, 1H), 4.41(ABq, 2H,
J = 12.0 Hz), 4.42(ABq, 2H, J = 12.3 Hz), 4.43(dd, 1H, J = 5.3, 12.2 Hz), 4.56(dd,
1H, J = 3.0, 12.1 Hz), 4.63(d, 1H, J = 5.8 Hz), 5.25(d, 1H, J = 5.8.1 Hz), 5.37(s, 1H),
5.56(dd, 1H, J = 8.1, 9.8 Hz), 5.66(t, 1H, J = 9.8 Hz), 5.99(t, 1H, J = 9.6 Hz), 7.15–
7.56(m, 22H), 7.80–8.05(m, 8H); 13C NMR (125.76 MHz, CDCl3): d 63.0, 65.4,
69.6, 71.2, 72.0, 72.1, 72.4, 73.0, 74.2, 75.3, 77.0, 77.7, 99.7, 100.5, 127.5–129.9,
133.2, 133.2, 133.3, 133.5, 137.6, 137.8, 165.0, 165.2, 165.8, 166.1;
HRMS(MALDI-TOF) Calcd for C54H48O14Na, 943.2942; Found, 943.2950.
5. (a) Tanaka, T.; Huang, W. C.; Noguchi, M.; Kobyashi, A.; Shoda, S.-I. Tetrahedron
Lett. 2009, 50, 2154–2157; (b) Miura, M.; Kaga, H.; Sakurai, A.; Kakuchi, T.;
Takahashi, K. J. Anal. Appl. Pyrolysis 2004, 71, 187–199; (c) Kawamoto, H.;
Hatanaka, W.; Saka, S. J. Anal. Appl. Pyrolysis 2003, 70, 303–313; (d) Miura, M.;
Kaga, H.; Yoshida, T.; Ando, K. J. Wood Sci. 2001, 47, 502–506; (e) Huang, Y. F.;
Kuan, W. H.; Lo, S. L.; Lin, C. F. Bioresour. Technol. 2010, 101, 1968–1973; (f)
Kwon, G.-J.; Kuga, S.; Hori, K.; Ytagai, M.; Ando, K.; Hattori, N. J. Wood Sci. 2006,
52, 461–465; (g) Byramova, N. E.; Tuzikov, A. B.; Tyrtysh, T. V.; Bovin, N. V. Russ.
J. Bioorg. Chem. 2007, 33, 99–109; (h) Award, L.; Demange, R.; Zhu, Y.-H.; Vogel,
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C.; Chang, S.-W.; Lee, J.-C.; Wang, C.-C.; Wen, Y.-S. J. Am. Chem. Soc. 2001, 123,
3153–3154; (j) Boissiere-Junot, N.; Tellier, C.; Rabiller, C. J. Carbohydr. Chem.
1998, 17, 99–115; (k) Lafont, D.; Boullanger, P.; Banoub, J.; Descotes, G. Can. J.
Chem. 1990, 68, 828–835; (l) Sakairi, N.; Hayashida, M.; Kuzuhara, H.
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Res. 1987, 162, 141–144; (n) Fujimaki, I.; Ichikawa, Y.; Kuzuhara, H. Carbohydr.
(f) Compound characterization data for compound 16: ½a D25
ꢀ
(CHCl3, c 1.3)
+47.4; 1H NMR (400.13 MHz, CDCl3): d 3.05(s, 1H), 3.33(m, 1H), 3.38(s, 1H),
3.49(t, 1H, J = 6.3 Hz), 3.65–3.98(m, 5H), 4.14(t, 1H, J = 9.7 Hz), 4.15(d, 1H,
J = 8.1 Hz), 4.44(ABq, 2H, J = 12.2 Hz), 4.38–4.64(m, 5H), 4.71(m, 1H), 4.86(d,
1H, J = 7.8 Hz), 5.22(s, 1H), 5.31(dd, 1H, J = 8.1, 9.9 Hz), 5.44(dd, 1H, J = 3.3,
10.3 Hz), 5.64(t, 1H, J = 9.4 Hz), 5.78(m, 1H), 7.05–8.15(m, 45H); 13C NMR
(125.76 MHz, CDCl3): d 61.0, 61.9, 64.6, 67.4, 69.9, 70.9, 71.2, 71.3, 71.6, 72.3,
72.5, 72.8, 73.8, 74.9, 75.0, 75.7, 76.2, 99.7, 100.2, 101.0, 127.6–130.0, 133.1,
133.2, 133.3, 133.4, 133.5, 133.6, 133.6, 137.6, 137.9, 164.7, 165.0, 165.2, 165.3,
165.4, 165.6, 165.7; HRMS(MALDI-TOF) Calcd for C81H70O22Na, 1417.4256;
Found, 1417.4251.
(g) Compound characterization data for compound 17: ½a D25
ꢀ
(CHCl3, c 1.2)
ˇ
ˇ
Res. 1982, 101, 148–151; (o) Cerny´, M.; Stanek, J. Adv. Carbohydr. Chem.
Biochem. 1977, 34, 23–177; (p) Shafizadeh, F.; Furneaux, R. H.; Stevenson, T. T.;
Cochran, T. G. Carbohydr. Res. 1978, 67, 433–447; (q) Hann, R. M.; Hudson, C. S.
J. Am. Chem. Soc. 1942, 64, 2435–2438.
+28.2; 1H NMR (500.13 MHz, CDCl3): d 3.23(s, 1H), 3.54(dd, 1H, J = 6.1, 7.1 Hz),
3.58(td, 1H, J = 3.3, 6.1, 10.3 Hz), 3.63(dd, 1H, J = 6.7, 11.4 Hz), 3.66(m, 1H),
3.72(dd, 1H, J = 6.7, 11.3 Hz), 3.76–3.94(m, 2H), 4.18–4.63(m, 9H), 4.89(ABq,
2H, J = 7.7 Hz), 5.34(d, 1H, J = 1.1 Hz), 5.35(dd, 1H, J = 3.5, 10.6 Hz), 5.49(dd, 1H,
J = 8.1, 10.2 Hz), 5.69–5.77(m, 3H), 7.05–8.08(m, 45H); 13C NMR (125.76 MHz,
CDCl3): d 61.1, 62.2, 65.3, 67.5, 69.9, 71.0, 71.4, 71.8, 71.8, 71.9, 73.0, 73.1, 74.3,
75.0, 75.8, 76.0, 78.7, 100.4, 100.5, 101.0, 127.4–130.0, 133.1, 133.2, 133.3,
133.4, 133.4, 133.4, 133.5, 137.6, 139.9, 164.7, 165.0, 165.2, 165.4, 165.4, 165.6,
6. (a) Hotha, S.; Kashyap, S. J. Am. Chem. Soc. 2006, 128, 9620–9621; (b) Kashyap,
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165.8; HRMS(MALDI-TOF) Calcd for
1417.4251.
C81H70O22Na, 1417.4256; Found,