N,N-Dibenzyl-9-{(3S,5S)-2-benzyl-3-[2,3-O-isopropylidene-1-O-methyl-α-D-lyxotetrafuranose]iso-
2
5
xazolidin-5-yl}adenine (5a). Yield 38%, colorless oil, R
f
0.47 (hexanes : AcOEt, 50 : 50). [α]
D
= +75
1
(
c = 0.12, CH Cl ). H NMR spectrum, δ, ppm (J, Hz): 8.42, 8.39 (2 × 1H, 2 × s, H-2'', H-8''); 7.27 (15H, m,
2
2
H-arom); 6.58 (1H, dd, J = 7.7, J = 2.9, H-5); 5.63–4.92 (4H, br.s, N(CH Ph) ); 4.88 (1H, s, H-2'); 4.65 (1H, dd,
2
2
J = 5.8, J = 2.9, H-4'); 4.52 (1H, d, J = 5.8, H-3'); 4.27 (1H, d, J = 14.4, NCH Ph); 4.07 (1H, d, J = 14.4,
2
NCH Ph); 3.93 (1H, dd, J = 3.8, J = 3.9, H-5'); 3.49 (1H, m, H-3); 3.20 (3H, s, OCH ); 3.12 (1H, m, H-4b);
2
3
1
3
3
.00 (1H, m, H-4a); 1.41 (3H, s, CH ); 1.27 (3H, s, CH ). C NMR spectrum, δ, ppm (J, Hz): 152.02, 137.61
3
3
(
C-2'', C-8''); 154.67, 150.42, 138.08, 127.24, 119.12 (NCH Ph, N(CH Ph) , C-adenine); 112.54 (C(CH ) );
2 2 2 3 2
1
06.60 (C-2'); 84.65 (C-3'); 80.89 (C-5); 79.72 (C-4'); 77.95 (C-5'); 63.80 (C-3); 61.88 (NCH Ph); 54.58
2
(
OCH ); 38.82 (C-4); 25.66 (CH ); 24.28 (CH ). Found, %: C 68.44; H 6.22; N 13.00. C H N O .
3 3 3 37 40 6 5
Calculated, %: C 68.50; H 6.21; N 12.95.
N,N-Dibenzyl-9-{(3S/3R,5S/5R)-2-benzyl-3-[2,3-O-isopropylidene-1-O-methyl-α-D-lyxo-tetrafura-
nose]isoxazolidin-5-yl}adenine (5b). Yield 20%, colorless oil, R 0.43 (hexanes : : AcOEt = 50 : 50).
f
2
5
1
[
(
(
α]D = +39 (c = 0.10, CH Cl ). H NMR spectrum, δ, ppm (J, Hz): 8.44, 7.92 (2 × 1H, 2 × s, H-2'', H-8''); 7.28
2
2
15H, m, H-arom); 6.41 (1H, dd, J = 7.0, J = 3.4, H-5); 5.64–4.92 (4H, br.s, N(CH Ph) ); 4.91 (1H, s, H-2'); 4.74
2
2
1H, dd, J = 5.9, J = 3.4, H-4'); 4.58 (1H, d, J = 5.9, H-3'); 4.26 (1H, d, J = 13.8, NCH Ph); 4.19 (1H, d,
2
J = 13.8, NCH Ph); 4.09 (1H, m, H-5'); 4.00 (1H, m, H-3); 3.36 (3H, s, OCH ); 3.26 (1H, m, H-4b); 3.14 (1H,
2
3
1
3
m, H-4a); 1.40 (3H, s, CH ); 1.27 (3H, s, CH ). C NMR spectrum, δ, ppm (J, Hz): 154.69, 137.51 (C-2'', C-8'');
3
3
1
52.37, 150.50, 137.13, 127.29, 120.01 (NCH Ph, N(CH Ph) , C-adenine); 112.46 (C(CH ) ); 106.95 (C-2');
2 2 2 3 2
8
5.05 (C-3'); 83.94 (C-5); 79.60 (C-4'); 79.17 (C-5'); 62.57 (C-3); 61.78 (NCH Ph); 54.79 (OCH ); 37.79 (C-4);
2 3
2
5.89 (CH ); 24.55 (CH ). Found, %: C 68.58; H 6.51; N 13.19. C H N O . Calculated, %: C 68.50; H 6.21;
3 3 37 40 6 5
N 12.95.
N,N-Dibenzyl-9-{(3R,5R)-2-benzyl-3-[2,3-O-isopropylidene-1-O-methyl-α-D-lyxo-tetrafuranose]iso-
2
5
xazolidin-5-yl}adenine (5c). Yield 19%, colorless oil, R 0.57 (hexanes : AcOEt = 50 : 50). [α]
= -12
f
D
1
(
c = 0.20, CH Cl ). H NMR spectrum, δ, ppm (J, Hz): 8.36, 8.06 (2 × 1H, 2 × s, H-2'', H-8''); 7.33 (15H, m,
2
2
H-arom); 6.41 (1H, m, H-5); 5.60-4.95 (4H, br.s, N(CH Ph) ); 4.95 (1H, s, H-2'); 4.77 (1H, d, J = 14.4,
2
2
NCH Ph); 4.65 (1H, dd, J = 6.3, 3.8, H-4'); 4.53 (1H, d, J = 6.7, H-3'); 4.09 (1H, m, H-5'); 3.93 (1H, d, J = 14.4,
2
NCH Ph); 3.43 (2H, m, H-4b, H-3); 3.32 (3H, s, OCH ); 2.39 (1H, m, H-4a); 1.49 (3H, s, CH ); 1.29 (3H, s,
2
3
3
1
3
CH3). C NMR spectrum, δ, ppm (J, Hz): 154.63, 137.53 (C-2'', C-8''); 152.08, 149.83, 136.88, 127.23,
1
19.37 (NCH Ph, N(CH Ph) , (C-adenine); 112.72 (C(CH ) ); 107.44 (C-2'); 84.26 (C-3'); 81.56 (C-5);
2 2 2 3 2
8
1.23 (C-4'); 80.82 (C-5'); 64.73 (C-3); 61.88 (NCH Ph); 54.55 (OCH ); 41.55 (C-4); 26.03 (CH ); 24.70 (CH ).
2
3
3
3
Found, %: C 68.03; H 6.61; N 12.69. C H N O . Calculated, %: C 68.50; H 6.21; N 12.95.
3
7
40
6
5
N,N-Dibenzyl-9-{(3S/3R,5S/5R)-2-benzyl-3-[2,3-O-isopropylidene-1-O-methyl-α-D-lyxotetrafuranose]-
2
5
isoxazolidin-5-yl}adenine (5d). Yield 18%, colorless oil, R
f
0.23 (hexanes : : AcOEt = 50 : 50). [α]
D
= −29.2 (c =
1
0
.12, CH Cl ). H NMR spectrum, δ, ppm (J, Hz): 8.39, 7.77 (2 × 1H, 2 × s, H-2'', H-8''); 7.32 (15H, m, H-arom); 6.37
2
2
(
1H, dd, J = 7.7, J = 2.9, H-5); 5.63–4.92 (4H, br.s, N(CH Ph) ); 4.99 (1H, s, H-2'); 4.73 (1H, dd, J = 5.8, J = 3.8, H-4');
2 2
4
.60 (1H, d, J = 14.4, NCH Ph); 4.58 (1H, d, J = 5.8, H-3'); 4.15 (1H, m, H-5'); 4.15 (1H, d, J 14.4, NCH Ph); 3.76 (1H,
2
2
m, H-3); 3.37 (3H, s, OCH ); 2.96 (1H, ddd, J = 8.6, J = 6.7, J = 1.9, H-4b); 2.78 (1H, m, H-4a); 1.46 (3H, s, CH ); 1.28
3
3
13
(
3H, s, CH ). C NMR spectrum, δ, ppm (J, Hz): 154.80, 137.67 (C-2'', C-8''); 152.55, 150.44, 136.76, 127.24,
3
1
19.70 (NCH Ph, N(CH Ph) , C-adenine; 112.71 (C(CH ) ); 107.42 (C-2'); 84.34 (C-3'); 81.40 (C-5); 80.71 (C-4');
2
2
2
3 2
8
0.56 (C-5'); 62.66 (C-3); 61.15 (NCH Ph); 54.66 (OCH ); 39.27 (C-4); 26.08 (CH ); 24.73(CH ).
2
3
3
3
1
,3-Dipolar cycloaddition of nitrone 3 with vinyl acetate. A mixture of nitrone 3 (0.5 g, 1.60 mmol)
and vinyl acetate (5 ml) was stirred for 24 h under reflux. When the starting nitrone had been consumed (TLC),
solvent was evaporated under vacuum and the mixture of diastereoisomers in the ratio 47 : 21 : 18 : 14 in 86%
yield was separated by column chromatography (silica gel, hexanes : AcOEt = 90 : 10).
(
3R,5S)-5-Acetoxy-2-benzyl-3-(2,3-O-isopropylidene-1-O-methyl-α-D-lyxotetrafuranose)isoxazo-
25
lidine (6a). Yield 35%, colorless oil, R 0.54 (hexanes : AcOEt = 50 : 50). [α] = +154.5 (c = 0.10, CH Cl ).
H NMR spectrum, δ, ppm (J, Hz): 7.32 (5H, m, H-arom); 6.45 (1H, d, J = 5.3, H-5); 4.83 (1H, s, H-2');
f
D
2
2
1
1
4