I. Matsuo et al. / Tetrahedron Letters 43 (2002) 3273–3275
3275
OR1
O
OBn
O
OBn
NPhth
NPhth
O
OAc
BnO
O
O
BnO
O
O
O
O
O
OAll
O
O
OAll
NPhth
2
O BnO
(i) or (ii)
R O
BDPSO
O BnO
NPhth
BnO
BnO
R1 R2
1
3
1
4
5
Ac
H
H
1
Ac
Scheme 1. (i) 10% HF/Pyr in DMF, 1 GPa, 14 (88%); (ii) TBAF/AcOH in DMF, 14 (50%), 15 (32%).
transformation was problematic. Namely, while HF–
pyridine gave no reaction, desilylation by TBAF/
AcOH in DMF was accompanied by an extensive
migration of the acetyl group to afford a mixture of
4. Manuscript in preparation. A brief summary of the
synthetic route to 1 is available on request.
5. Helenius, A.; Aebi, M. Science 2001, 291, 2364–2369.
6. Corey, E. J.; Venkateswarlu, A. J. Am. Chem. Soc.
1972, 94, 6190–6191.
2-O-Ac (14) and 3-O-Ac (15) products. By contrast,
under high pressure conditions, HF/pyridine in DMF
gave compound 14 as a single product in 88% yield
7. Newton, R. F.; Reynols, D. P. Tetrahedron Lett. 1979,
20, 3981–3982.
(
Scheme 1).
8
. (a) Nicolaou, K. C.; Setitz, S. P.; Pavia, M. R.; Petasis,
N. A. J. Org. Chem. 1979, 44, 4011–4013; (b) Hay-
ward, C. M.; Yohannes, D.; Danishefsky, S. J. J. Am.
Chem. Soc. 1993, 115, 9345–9346.
In conclusion, deprotection of TBDPS ether residing
at sterically hindered position was achieved using HF/
14
pyridine in DMF under high pressure. The present
method may provide a rescue whenever desilylation
proceeds with low reaction rate and/or is accompa-
nied by unfavorable side reaction(s).
9. Scheidt, K. A.; Chen, H.; Follows, B. C.; Chemler, S.
R.; Coffey, D. S.; Roush, W. R. J. Org. Chem. 1998,
63, 6436–6437.
1
1
0. Furusawa, K. Chem. Lett. 1989, 509–510.
1. Higashibayashi, S.; Shinko, K.; Ishizu, T.; Hashimoto,
K.; Shirahama, H.; Nakata, M. Synlett 2000, 1306–
Acknowledgements
1308.
1
2. (a) Dauben, W. G.; Bunce, R. A.; Gerdes, J. M.; Hene-
gar, K. E.; Couningham, A. F., Jr.; Ottoboni, T. B.
Tetrahedron Lett. 1983, 5709–5712; (b) Dauben, W. G.;
Gerdes, J. M.; Look, G. C. Synthesis 1986, 532–535; (c)
Matsumoto, K.; Acheson, R. M. Organic Synthesis at
High Pressures; John Wiley & Sons: New York, 1991.
3. A typical procedure: To a 1 mL Teflon reaction vessel
was introduced compound 1 (96.9 mg, 0.022 mmol) dis-
solved in DMF (0.8 mL) containing 10% HF/pyridine
We thank Dr. Teiji Chihara for the operation of the
high pressure equipment and Ms. Akemi Takahashi
for technical assistance. Financial support from Mizu-
tani Foundation for Glycoscience and Ministry of
Education, Culture, Sports, Science and Technology
1
[
1
Grant-in-Aid for Scientific Research (B) No.
3480191] are acknowledged.
(
3
Aldrich). It was compressed to 1.0 GPa and left at
0°C for 12 h and the resulting mixture was diluted
References
with AcOEt and washed with sat. aq. NaHCO3 and
brine, successively. The organic layer was dried over
MgSO4 and evaporated in vacuo. The residue was
purified by silica gel column chromatography (hexane–
1
. (a) Greene, T. W.; Wuts, P. G. M. Protective Groups in
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AcOEt, 10:1–1:2) to afford 78.9 mg (86%) of com-
1
pound 2; R 0.28 (1:1 toluene–EtOAc); H NMR (400
2
f
MHz, CDCl ) l 7.79–6.71 (m, Ar), 5.65–5.54 (1H, m,
2
975–2977.
3
CH ꢀC H6 ), 2.10–1.88 (48H, s×14, Ac); MALDI-TOF
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. (a) Rucker, C. Chem. Rev. 1995, 95, 1009–1064; (b)
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2
+
mass: calcd for C222H N NaO [M+Na] , 4144.5.
244
2
74
Found: 4144.2. Anal. calcd for C222H244N O : C,
2
74
6
0
4.65; H, 5.96; N, 0.68. Found: C, 64.44; H, 5.97; N,
.65.
1
1
4. The RIKEN high pressure apparatus is capable of
holding a 50 mL reaction volume at 2.0 GPa and scal-
ing up to multigram should be straightforward.
2
109–2135; (f) Jarowicki, K.; Kocienski, P. J. Chem.
Soc., Perkin Trans. 1 1999, 1589–1615.