G. Coste, S. Gerber-Lemaire / Tetrahedron Letters 47 (2006) 671–674
673
corresponding polyol 11 in 58% yield. Treatment with
Me2C(OMe)2 and acetone, in the presence of a catalytic
amount of p-TsOH, afforded diacetonide 12. The condi-
tions described above were successfully applied to this
derivative, resulting in the selective cleavage of the
anti-1,3-diol-acetonide to provide monoacetonide 13 in
70% yield. In synthetic studies, silyl groups are among
the most widely used protecting moieties for alcohols.
For that purpose we also tested the compatibility of
our conditions with tert-butyldimethylsilyl groups as
exemplified by the selective deprotection of the 1,3-anti
diol moiety from the silylated polyol 14, in the presence
of 5 mol % of p-toluenesulfonic acid, which provided
monoacetonide 15 in 68% yield. No trace of deprotec-
tion of the primary alcohols was observed.
12H) ppm. 13C NMR (C6D6, 100.6 MHz, 25 °C):
d = 139.1, 129.3, 129.2, 128.5, 101.1, 99.3, 95.6, 95.5,
75.3, 74.3, 70.4, 66.6, 65.9, 64.5, 63.0, 60.0, 43.7, 43.4,
43.1, 40.1, 39.3, 39.2, 31.2, 25.8, 25.7, 20.6 ppm. CI-
MS (NH3): 678 (1, ½MþNHþ4 ꢁ), 645 (2), 91 (100).
C37H56O10 (660.839): calcd C 67.25, H 8.54; found C
67.25, H 8.79.
Data for 13. IR (film): 3415, 2945, 1650, 1430, 1285,
1
1200, 1160, 1100, 1035, 740, 700 cmꢀ1. H NMR (400
MHz, MeOD): d = 7.38–7.15 (m, 10H), 4.83–4.78
(s, 4H), 4.67–4.60 (m, 4H), 4.12–3.95 (m, 6H), 3.70–
3.65 (m, 4H), 1.82–1.75 (m, 4H), 1.62–1.29 (2m, 10H),
1.39, 1.30 (2s, 6H) ppm. 13C NMR (100 MHz, MeOD):
d = 138.3, 128.4, 128, 127.7, 99.0, 94.6, 94.5, 73.4, 72.8,
69.8, 69.7, 66.3, 66.0, 65.1, 64.6, 58.5, 58.4, 45.8, 44.7,
43.7, 42.9, 38.5, 38.3, 38.1, 29.6, 19.3 ppm. MALDI-
MS: 643.31 (M+Na), 659.28 (M+K). C34H52O10
(620.775): calcd C 65.78, H 8.44; found C 65.72, H 8.35.
3. Conclusion
The differentiation of alcohol moieties from polyolic
fragments is often required for the selective functionali-
zation of synthetic intermediates. In this context, the
mild conditions reported here represent a new alterna-
tive for the selective deprotection of anti-1,3-diols from
polyacetonide derivatives.
Data for 15. IR (film): 3520, 2940, 2860, 1733, 1465,
1380, 1255, 1200, 1165, 1105, 1040, 840, 780, 740, 700,
1
660 cmꢀ1. H NMR (400 MHz, MeOD): d = 7.50–7.24
(m, 10H), 4.83 (s, 4H), 4.26, 4.63 (2s, 4H), 4.20–3.85
(2m, 6H), 3.74 (t, 4H, 3J = 5.7), 1.78–1.40 (m, 4H),
1.78–1.40 (2m, 10H), 1.42, 1.28 (2s, 6H), 0.92 (s, 18H),
0.13 (s, 12H) ppm. 13C NMR (100 MHz, MeOD):
d = 138.3, 128.4, 127.9, 127.7, 98.9, 94.6, 94.5, 73.5,
69.8, 67.5, 66.2, 65.3, 64.4, 59.7, 44.7, 44.4, 43.8, 43.3,
38.8, 37.6, 29.6, 19.3, 25.4, 24.1, ꢀ6.2 ppm. MALDI-
MS: 871.61 (M+Na), 887.58 (M+K). C46H80O10Si2
(849.292): calcd C 65.05, H 9.49, Si 6.61; found C
65.75, H 9.55, Si 6.54.
3.1. General procedure for the selective hydrolysis
The polyacetonide derivative was dissolved in dichloro-
methane (concentration: 0.05 M) and the solution was
cooled to ꢀ20 °C. p-Toluene sulfonic acid (0.05 equiv)
was added and the mixture was stirred at ꢀ20 °C for
3 h (monitoring by TLC). The reaction mixture was
directly purified by flash chromatography (4% MeOH/
CH2Cl2) to afford the monodeprotected derivative as a
colorless oil. Otherwise, the reaction mixture could also
be worked-up by pouring into a satd aq solution of
NaHCO3. The aqueous layer was extracted with CH2Cl2
(three times). The combined organic extracts were dried
(MgSO4) and concentrated in vacuo. The residue was
purified as mentioned above.
Acknowledgements
This work was supported by the Swiss National Foun-
dation (Grant No. 200020-100028/1). We thank Mr.
Martial Rey and Mrs Annabelle Gillig for technical
help.
23
23
23
23
Data for 7. ½aꢁ405 ꢀ223, ½aꢁ435 ꢀ120, ½aꢁ577 ꢀ22, ½aꢁ589 ꢀ10
References and notes
(c 0.4, MeOH). IR (film): 3415, 2940, 1650, 1430, 1380,
1265, 1200, 1160, 1100, 1035, 740, 700 cmꢀ1. H NMR
1
1. For leading reviews, see e.g.: (a) Aparicio, J. F.; Mendes,
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(400 MHz, MeOD): d = 7.38–7.24 (m, 10H), 4.82 (s,
4H), 4.64–4.60 (m, 4H), 4.13–4.09 (m, 2H), 4.08–3.96
(m, 4H), 3.67 (t, 4H, 3J = 6.7), 1.82–1.77 (m, 4H),
1.69–1.65, 1.63–1.42 (2m, 10H), 1.42, 1.29 (2s, 6H)
ppm. 13C NMR (100 MHz, MeOD): d = 138.8, 128.4,
127.9, 127.7, 98.9, 94.5, 94.4, 73.5, 73.4, 69.8, 67.5,
66.2, 65.3, 64.4, 58.5, 44.8, 44.4, 43.7, 43.1, 38.4, 38.3,
37.6, 29.6, 19.2 ppm. MALDI-MS: 643.46 (M+Na),
659.45 (M+K). C34H52O10 (620.775): calcd C 65.78, H
8.44; found C 65.75, H 8.49.
Data for 12. IR (film): 3445, 3065, 3030, 2990, 2940,
1495, 1455, 1380, 1225, 1165, 1025, 940, 810, 740,
700 cmꢀ1
.
1H NMR (C6D6, 400 MHz, 25 °C):
d = 7.33–7.06 (m, 10H), 4.77–4.70 (m, 4H), 4.62, 4.50
(2d, 2H, 2J = 12.0), 4.61, 4.47 (2d, 2H, 2J = 12.0),
4.21–3.86 (m, 6H), 3.74, 3.64 (2m, 4H), 2.05–1.98 (m,
4H), 1.78–1.31 (m, 10H), 1.40, 1.38, 1.33, 1.27 (4s,
´
3. (a) Csaky, A. G.; Vogel, P. Tetrahedron: Asymmetry 2000,
¨
11, 4935–4944; (b) Gerber-Lemaire, S.; Vogel, P. Eur. J.
Org. Chem. 2003, 2959–2963.