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Lett. 2005, 46, 8047–8051; (d) Booma, C.; Balasubramani-
an, K. K. Tetrahedron Lett. 1993, 34, 6757–6760; (e) Wolf,
J.; Monneret, C.; Pontikis, R.; Florent, J.-C. Eur. J. Org.
Chem. 1998, 2417–2423; (f) Ramesh, N. G.; Balasubrama-
nian, K. K. Tetrahedron 1995, 51, 255–272.
In addition, we have also shown that the per-O-benzyl-
ated C-2-propargyloxymethyl galactal 4 and per-O-
benzylated C-2-propargyloxymethyl xylal 6 also react
with aglycones to give the corresponding C-2 methylene
galactosides and xylosides, respectively, in a stereoselec-
tive manner (Table 1). For example, galactal and xylal-
derived enynes (4 and 6) reacted with pentenyl alcohol
to give C-2 methylene-containing pentenyl galactoside
5a and C-2 methylene-bearing pentenyl xylopyranoside
7a in 68% and 60% yields, respectively.7 It is interesting
to note that alicyclic (Table 1, entry 2) and sugar-derived
aglycones (Table 1, entries 3–5) also reacted with enyne
4 to give the corresponding galactosides (5b–5e).7
4. (a) Maurya, S. K.; Hotha, S. Tetrahedron Lett. 2006, 47,
3307–3310; (b) Hotha, S.; Tripathi, A. J. Comb. Chem.
2005, 7, 968–976; (c) Hotha, S.; Maurya, S. K.; Gurjar, M.
K. Tetrahedron Lett. 2005, 46, 5329–5332; (d) Hotha, S.;
Anegundi, R. I.; Natu, A. A. Tetrahedron Lett. 2005, 46,
4585–4588.
5. (a) Kashyap, S.; Hotha, S. Tetrahedron Lett. 2006, 47,
2021–2023; (b) Hotha, S.; Kashyap, S. J. Am. Chem. Soc.
2006, 128, 9620–9621.
6. (a) Ramesh, N. G.; Balasubramanian, K. K. Tetrahedron
Lett. 1991, 32, 3875–3878; For a review on C-2 formyl
glycals, see: (b) Ramesh, N. G.; Balasubramanian, K. K.
Eur. J. Org. Chem. 2003, 4477–4487.
In summary, we have synthesized C-2 methylene glyco-
sides from stable propargyloxymethyl glycals exploiting
gold catalysis. The current protocol enables the activa-
tion of an alkyne group in the presence of various func-
tional groups. Our efforts in utilizing these glycosides
possessing an exomethylene group at the C-2 position
for the preparation of diverse molecular skeletons will
be reported in the future.
7. All products gave satisfactory 1H, 13C, DEPT NMR and
MS analysis. See Supplementary data.
8. General experimental procedure: To a solution of compound
2 (1 mmol) in anhydrous acetonitrile (5 mL) were added
aglycone (2 mmol) and AuCl3 (5 mol% in acetonitrile) at
0 °C and the resulting mixture was stirred at rt for 16 h. The
reaction mixture was concentrated in vacuo, the crude
residue was redissolved in ethyl acetate and washed with
water. The combined organic layers were dried over
anhydrous Na2SO4, concentrated in vacuo and the resulting
residue was purified by silica gel column chromatography
using light petroleum ether (60–80 °C) and ethyl acetate to
afford exomethylene a-glucosides in good yields.
9. Characterization data of compound 2: [a]D +69.2 (CHCl3, c
2.00); 1H NMR (CDCl3, 200.13 MHz): 2.38 (t, 1H,
J = 2.39 Hz), 3.74 (dt, 2H, J = 3.77, 5.22 Hz), 3.86 (d,
1H, J = 11.36 Hz), 3.90 (dd, 1H, J = 5.22, 6.54 Hz), 4.08 (t,
2H, J = 2.39 Hz), 4.14–4.32 (m, 3H), 4.53 (s, 2H), 4.64 (s,
2H), 4.67 (ABq, 2H, J = 11.68 Hz), 6.51 (s, 1H), 7.22–7.34
(m, 15H); 13C NMR (CDCl3, 50.32 MHz): 55.6, 66.9, 67.9,
72.6, 72.8, 73.2, 73.5, 73.9, 74.3, 76.4, 79.7, 108.6, 127.4–
128.3, 137.7, 137.8, 138.2, 144.3; calcd mass for C31H32O5:
484.58; found, 507.05 (M+23 for Na).
Acknowledgements
S.H. thanks the DST, New Delhi (SR/S1/OC-06/2004)
for financial support. S.H. is grateful for the encourage-
ment of Dr. K.N. Ganesh. S.K. and S.R.V. acknowl-
edge a fellowship from CSIR-New Delhi. The authors
thank the reviewer for suggestions.
Supplementary data
Supplementary data associated with this article can be
Characterization data of compound 3a: [a]D +28.9 (CHCl3, c
1.10); 1H NMR (CDCl3, 200.13 MHz): 3.38 (s, 3H), 3.61 (t,
1H, J = 9.42 Hz), 3.70–3.75 (m, 2H), 3.92 (m, 1H), 4.40–
4.90 (m, 7H), 5.06 (s, 1H), 5.16 (dd, 1H, J = 1.25, 2.00 Hz),
5.30 (dd, 1H, J = 1.25, 2.00 Hz), 7.10–7.42 (m, 15H); 13C
NMR (CDCl3, 50.32 MHz): 54.4, 68.8, 71.5, 73.4, 73.4,
74.9, 80.0, 81.2, 102.4, 110.7, 127.5–128.4, 138.1, 138.2,
138.3, 142.4; calcd mass for C29H32O5: 460.56; found,
483.04 (M+23 for Na).
References and notes
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Characterization data of compound 3b: [a]D +37.9 (CHCl3, c
1
1.20); H NMR (CDCl3, 200.13 MHz): 3.68 (m, 3H), 4.00
(m, 1H), 4.37–4.92 (m, 9H), 5.13 (dd, 1H, J = 1.31,
1.99 Hz), 5.26 (s, 1H), 5.30 (dd, 1H, J = 1.31, 1.99 Hz),
7.08–7.43 (m, 20H); 13C NMR (CDCl3, 50.32 MHz): 68.8,
68.9, 71.8, 73.4, 73.5, 75.0, 80.1, 81.3, 100.8, 110.8, 127.4–
128.4, 137.5, 138.2, 138.3, 138.4, 142.3; calcd mass for
C35H36O5: 536.67; found, 559.04 (M+23 for Na).
Characterization data of compound 3f: [a]D +37.2 (CHCl3, c
1
1.20); H NMR (CDCl3, 200.13 MHz): 1.30, 1.42 (2s, 6H),
2. (a) Matsuda, A.; Takenuki, K.; Tanaka, M.; Saski, T.;
Ueda, T. J. Med. Chem. 1991, 34, 812–819; (b) Agelis, G.;
3.31 (s, 3H), 3.48–3.91 (m, 5H), 4.08 (m, 2H), 4.41–4.92 (m,
10H), 5.16 (dd, 1H, J = 1.26, 1.87 Hz), 5.23 (s, 1H), 5.30
(dd, 1H, J = 1.26, 1.87 Hz), 7.12–7.42 (m, 15H); 13C NMR
(CDCl3, 50.32 MHz): 25.0, 26.1, 54.6, 64.8, 68.7, 71.6, 73.3,
73.4, 74.9, 78.1, 79.7, 80.0, 81.1, 84.9, 101.4, 107.1, 110.7,
112.5, 127.5–128.4, 138.1, 138.2, 138.4, 142.3; calcd mass
for C37H44O9: 632.74; found, 655.84 (M+23 for Na).
´
ˇ
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