J.-P. Uttaro et al. / Tetrahedron Letters 48 (2007) 3851–3854
3853
NH2
N
O
N
O
O
O
O
O
PhSO2H2C
PhSO2H2C
PhSO2H2C
OH
11
b
NH2
NHBz
N
N
HO
O
N
O
N
a
OH
O
O
O
compound 4
X
OH
OAc
10
c
NHBz
N
O
N
O
O
OH
12
Scheme 5. Reagents and conditions: (a) N4-Bz cytosine, BSA, CH3CN, reflux, 2 h then compound 4, TMSOTf, 0 °C to rt, 12 h, then reflux 4 h, 75%;
(b) KOH, EtOH, reflux, 8 h, 76%; (c) LiNH2, NH3/THF, ꢀ50 °C to rt, 89%.
7. Selected physicochemical data for compound 4. 1H NMR
tion. Nevertheless, the reactivity of the PSE acetal moiety
(300 MHz, CDCl3, 20 °C): d 1.98 (s, CH3a), 2.00 (s,
CH3b), 2.07 (s, CH3b), 3.44 (br d, J = 5.0 Hz, 2H, H-a and
H-b), 3.90 and 4.12 (ABX, J = 13.5, 2.0 Hz, 2H, H-5a),
3.90 and 4.18 (AB, J = 12.8 Hz, 2H, H-5b), 3.97 (br s, 1H,
H3-b), 4.04 (br s, 1H, H-3a), 4.26 (d, 1H, H-4a and H-4b),
4.81 (s, 1H, H-2b), 4.94 (d, 1H, J = 4.5 Hz, H-2a), 5.02 (t,
J = 5.0 Hz, 1H, H-6a and H-6b), 5.97 (s, 1H, H-1b), 6.34
(d, J = 4.5 Hz, 1H, H-1a), 7.51–7.56 (m, 2H), 7.61–7.66
(m, 1H), 7.85–7.88 (m, 2H) ppm. 13C NMR (75 MHz,
CDCl3, 20 °C): d 20.3 (CH3a), 20.6 (CH3b), 20.7 (CH3a),
21.0 (CH3b), 60.0 (C-7a), 60.2 (C-7b), 65.8 (C-5a), 66.0
(C-5b), 72.2 (C-3a), 74.4 (C-3b), 75.9 (C-4b), 76.3 (C-2a),
78.4 (C-4a), 80.1 (C-2b), 94.5 (C-6b), 94.8 (C-6a), 95.4 (C-
1a), 99.9 (C-1b), 128.2 (CHarom), 128.9 (CHarom), 133.8
(CHarom), 133.9 (CHarom), 139.8 (Carom), 139.9 (Carom),
169.0 (CO), 169.5 (CO). MS (FAB, GT) 423 (M+Na)+,
341 (MꢀAcOH)+.
appeared unusual; when introduced on a nucleoside skel-
eton, the removal of the protective group under basic
conditions does not follow a general rule, as being suc-
cessful in the case of adenine xylo-nucleoside, but unsuc-
cessful with xylo-nucleoside derivatives of uracil and
cytosine. The nature of the base (purine or pyrimidine)
seems to be at the origin of this different reactivity. In
order to confirm this hypothesis, further investigations
are in progress in our laboratory.
References and notes
1. De Clercq, E. J. Clin. Virol. 2004, 30, 115–133.
2. Matsuda, A.; Sasaki, T. Cancer Sci. 2004, 95, 105–111.
3. Ichikawa, E.; Kato, K. Curr. Med. Chem. 2001, 8, 385–
423.
8. Saneyoshi, M.; Satoh, E. Chem. Pharm. Bull. 1979, 27,
2518.
4. Chery, F.; Rollin, P.; De Lucchi, O.; Cossu, S. Synthesis
2001, 286–292.
9. Vorbruggen, H.; Krolikiewicz, K.; Bennua, B. Chem. Ber.
¨
1981, 114, 1234–1255.
5. (a) Cabianca, E.; Chery, F.; Rollin, P.; Tatiboue¨t, A.; De
Lucchi, O. Tetrahedron Lett. 2002, 43, 585–587; (b)
Chevalier-du Roizel, B.; Cabianca, E.; Tatiboue¨t, A.;
10. Baker, B. R. In The CIBA Foundation Symposium on the
Chemistry and Biology of the Purines; Wolstenholme, G.
E. W., O’Connor, C. M., Eds.; Churchill: London, 1957;
pp 120–133.
Rollin, P.; Sinay, P. Tetrahedron 2002, 58, 9579–9583; (c)
¨
Cabianca, E.; Tatiboue¨t, A.; Rollin, P. Polish J. Chem.
2005, 79, 317–322.
6. Gosselin, G.; Bergogne, M. C.; Imbach, J.-L. In Nucleic
Acid Chemistry, Improved and New Synthetic Procedures,
Methods and Techniques, Part 4; Townsend, L. B., Tipson,
R. S., Eds.; Wiley: New York, 1991; pp 41–45.
11. Selected physicochemical data for compound 5. Mp 123 °C.
1H NMR (300 MHz, CDCl3, 20 °C): d 2.17 (s, 3H, CH3),
3.43 (ddd, J = 14.7, 6.4, 4.2 Hz, 2H, H-70), 4.05 and 4.39
(ABX, J = 13.4, 1.8 Hz, 2H, H-50), 4.15 (br s, 1H, H-30),
4.30 (d, J = 2.2 Hz, 1H, H-40), 4.94 (s, 1H, H-20), 5.10 (dd,
J = 6.3, 4.3 Hz, 1H, H-60), 5.64 (br s, 2H, NH2), 6.16 (s,