O
N
O
N
O
N
3 A. B. Holmes, A. Kee, T. Ladduwahetty and D. F. Smith, J. Chem. Soc.,
Chem. Commun., 1990, 1412.
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61.
NH
NH
NH
O
O
O
i
H
ii
H
iii
H
7c
HO
HO
HO
HO
6
H. Baumgartner, C. Marschner, R. Pucher, M. Singer and H. Griengl,
Tetrahedron Lett., 1992, 33, 6443.
7
(a) V. K. Aggarwal, N. Monteiro, G. J. Tarver and S. D. Lindell, J. Org.
Chem., 1996, 61, 1192; (b) V. K. Aggarwal, N. Monteiro, G. J. Tarver
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H. Hagenmaier, A. Keckeisen, H. Z a¨ hner and W. A. K o¨ nig, Liebigs
Ann. Chem., 1979, 1494.
H
H
H
CO2Bn
CO2Bn
CO2H
ZHN
ZHN
H2N
9
10
, DMF, 90%; ii, OsO
11
8
9
t
Scheme 3 i, BnBr, NaHCO
THF, 18 h, 52%; iii, H Pd/C, EtOH, 2 h, 95%
3
4
, NMO·H
2
O, Bu OH,
2
H. Hagenmaier, A. Keckeisen, W. Dehler, H. P. Fiedler, H. Z a¨ hner and
W. A. K o¨ nig, Liebigs Ann. Chem., 1981, 1018.
1
0 W. A. K o¨ nig, W. Hass, W. Dehler, H. P. Fiedler and H. Z a¨ hner, Liebigs
Ann. Chem., 1980, 622.
We thank the EPSRC and the LINK Asymmetric Synthesis
Initiative (Chiroscience Ltd and the Department of Trade and
Industry) for financial support, the EPSRC Swansea Mass
Spectrometry Service for mass spectrometry data, Dr V. K.
Aggarwal for helpful advice and pre-prints of refs. 7b,c and
Professor J. M. Williams and Dr B. Adger for their interest in
this work.
1
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1
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Footnotes and References
*
†
E-mail: abh1@cus.cam.ac.uk
Preparation of the bis(trimethylsilyl)uracil 6 using Vorbr u¨ ggen or
1
992, 46, 686.
19
1
1
8 L. L. Gundersen, T. Benneche, F. Rise, A. Gogoll and K. Undheim, Acta
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2
0
Cossy methodology was, in our hands, difficult to reproduce consistently.
Development of the Benneche protocol using refluxing hexamethyldisila-
zane with a catalytic quantity of ammonium sulfate gave reproducibly good
results, provided the reflux time was prolonged to 3–4 h.
1
234.
2
2
2
0 J. Cossy and P. Pale, Tetrahedron Lett., 1987, 28, 6039.
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‡
All new compounds exhibited spectroscopic and combustion analysis (or
high resolution mass spectrometry) properties in accordance with the
assigned structures.
2
225.
2
3 G. Poli, Tetrahedron Lett., 1989, 30, 7385.
1
2
S. M. Weinreb, in Comprehensive Organic Synthesis, ed. B. M. Trost
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Received in Cambridge, UK, 11th August 1997; 7/05825J
2086
Chem. Commun., 1997