Helvetica Chimica Acta ± Vol. 83 (2000)
1973
3060m, 2931m, 2868m, 2836m, 1686s, 1608m, 1582m, 1508s, 1464s, 1446m, 1412m, 1363m, 1275m, 1252s, 1177s,
1155m, 1092s, 1070m, 1033s, 914m, 87 w4, 828m, 7 9m1 , 7 5m4 , 7 2m7 , 7 0m0 , 658w, 598m, 584m. 1H-NMR
(300 MHz, CDCl3): 8.72 (s, HÀN(3)); 7.80 (s, HÀC(6)); 7.41 ± 7.44 (m, 2 arom. H); 7.17 ± 7.34 (m, 12 arom. H);
6.79 ± 6.84 (m, 4 arom. H); 6.36 (dd, J 6.1, 7.5, HÀC(1')); 4.50 ± 4.54 (m, HÀC(3')); 4.28 (s, PhCH2); 4.03
(q, J 3.4, HÀC(4')); 3.98 (d, J 11.8, 1 H, CH2ÀC(5)); 3.77 (d, J 11.8, 1 H, CH2ÀC(5)); 3.74, 3.75 (2s,
2 MeO); 3.44 (dd, J 3.7, 10.7, 1 HÀC(5')); 3.37( dd, J 3.5, 10.7, 1 HÀC(5')); 2.42 (ddd, J 3.3, 5.9, 13.6,
1 HÀC(2')); 2.24 ± 2.33 (m, 1 HÀC(2'), OHÀC(3')). 13C-NMR (75 MHz, CDCl3): 162.55 (s, C(4)); 158.64
(s, arom. C); 150.25 (s, C(2)); 144.51 (s, arom. C); 138.52 (d, C(6)); 137.88, 135.52, 135.41 (3s, arom. C); 130.10,
128.29, 128.10, 128.01, 127.75, 127.58, 127.06, 113.29 (8d, arom. C); 112.21 (s, C(5)); 86.84 (s, CÀOÀC(5')); 86.02
(d, C(4')); 84.98 (d, C(1')); 72.88 (t, PhCH2); 72.33 (d, C(3')); 64.26 (t, CH2ÀC(5)); 63.51 (t, C(5')); 55.21
(q, MeO); 40.89 (t, C(2')). LSI-MS: 651 (0.3, MH ), 305 (3), 304 (26), 303 (100), 207(4), 135 (4), 125 (2).
N4-Benzoyl-5-[(benzyloxy)methyl]-2'-deoxy-5'-O-(4,4'-dimethoxytrityl)cytidine (17). Rf 0.38 (hexane/
AcOEt 1 :3). [a]2D5 53.0 (c 0.92, CHCl3). UV (EtOH): 234 (27260), 262 (sh, 11820), 326 (21050). IR
(KBr): 3435m (br.), 3062w, 3030w, 3000w, 2930m, 2868w, 2835w, 1707s, 1648m, 1606s, 1566s, 1508s, 1487m,
1463m, 1447m, 1412w, 1365m, 1334m, 1310m, 1276s, 1251s, 1175s, 1092s, 1067m, 1034m, 1002m, 914w, 828m,
791m, 7 5m4 , 7 1m4 , 7 0m0 , 680m, 584m. 1H-NMR (400 MHz, CDCl3): 13.37( s, NHÀC(4)); 8.21 (br. s,
2 arom. H); 8.07(br. s, HÀC(6)); 7.22 ± 7.53 (m, 17arom. H); 6.82 ± 6.85 ( m, 4 arom. H); 6.37( t, J 6.5,
HÀC(1')); 4.37(br. d, 1 H, PhCH2); 4.32 (br. d, 1 H, PhCH2); 4.24 (br. d, 1 H, CH2ÀC(5)); 4.10 (br. d, 1 H,
CH2ÀC(5)); 3.87± 3.93 (br. m, HÀC(4')); 3.753, 3.748 (2s, 2 MeO); 3.48 (br. dd, 1 HÀC(5')); 3.40 (dd, J 3.3,
10.7, 1 HÀC(5')); 2.71 (br. s, OHÀC(3')); 2.49 ± 2.56 (br. m, 1 HÀC(2')); 2.34 (pent, J 6.7, 1 HÀC(2')).
13C-NMR (100 MHz, CDCl3): 179.76 (s, PhCO); 158.70 (s, arom. C, C(4)); 147.78 (s, C(2)); 144.55 (s, arom. C);
139.69 (d, C(6)); 137.93, 137.01, 135.55, 135.45 (4s, arom. C); 132.51, 130.17, 130.15, 129.93, 128.43, 128.16, 128.07,
127.86, 127.73, 127.12, 113.34 (11d, arom. C); 112.67( s, C(5)); 86.94 (s, CÀOÀC(5')); 86.24 (d, C(4')); 85.69
(d, C(1')); 73.04 (t, PhCH2); 72.12 (d, C(3')); 64.56 (t, CH2ÀC(5)); 63.42 (t, C(5')); 55.25 (q, MeO); 41.36
(t, C(2')). LSI-MS: 754 (2, MH ), 337(5), 336 (17), 304 (22), 303 (100), 228 (13), 105 (32).
Phosphoramidites 18 and 19: General Procedure. The 2-cyanoethyl diisopropylphosphoramidochloridite
(1.50 mmol) was added to a soln. of 16 or 17 (1 mmol) and iPr2NEt (3.00 mmol) in THF (10 ml). After stirring
for 1 h at r.t., the reaction was quenched by addition of sat. aq. NaHCO3 soln., the mixture extracted twice with
CH2Cl2, the org. layer dried (Na2SO4) and evaporated, and the remaining crude product purified by FC with the
solvent indicated. For prep. chromatography, 1½ Et3N was added to the solvent to prevent detritylation and
hydrolysis of the phosphoramidite: 18 (92%) and 19 (91%), resp., both as brittle colorless foams.
5-[(Benzyloxy)methyl]-2'-deoxy-5'-O-(4,4'-dimethoxytrityl)uridine 3'-(2-Cyanoethyl Diisopropylphosphor-
amidite) (18). Rf 0.54, 0.44 (hexane/AcOEt 1:2). UV (EtOH): 235 (21980), 266 (11790). IR (KBr): 3185m
(br.), 3061m, 3034m, 2966s, 2931m, 2870m, 2837m, 2252w, 1694s, 1608m, 1583m, 1510s, 1463s, 1397m, 1364m,
1274s, 1252s, 1200m, 1179s, 1155m, 1086s, 1033s, 97 8s, 900m, 828s, 7 91m, 7 54m, 7 27m, 7 00m, 634w, 598m, 584m,
523m. 1H-NMR (400 MHz, CDCl3): 8.86 (s, HÀN(3)); 7.88, 7.84 (2s, HÀC(6)); 7.42 ± 7.45 (m, 2 arom. H); 7.15 ±
7.35 (m, 12 arom. H); 6.80 ± 6.84 (m, 4 arom. H); 6.38 (t, J 7.7, 0.5 H, HÀC(1')); 6.37( t, J 7.8, 0.5 H,
HÀC(1')); 4.61 ± 4.67( m, HÀC(3')); 4.24, 4.22 (2s, PhCH2); 4.13 ± 4.19 (m, HÀC(4')); 3.96 (d, J 12.3, 0.5 H,
CH2ÀC(5)); 3.94 (d, J 11.7, 0.5 H, CH ÀC(5)); 3.753, 3.745, 3.738 (3s, 2 MeO); 3.53 ± 3.88 (m, 5 H, 2 Me2CH,
2
OCH2CH2CN, 1 H of CH2ÀC(5)); 3.50 (dd, J 3.0, 10.6, 0.5 H, HÀC(5')); 3.45 (dd, J 3.1, 10.6, 0.5 H,
HÀC(5')); 3.31, 3.33 (2dd, J 3.3, 10.6, 1 H, HÀC(5')); 2.63 (t, J 6.2, 1 H, OCH2CH2CN); 2.56 (ddd, J 2.4,
5.7, 13.7, 0.5 H, HÀC(2')); 2.49 (ddd, J 3.0, 5.8, 13.5, 0.5 H, HÀC(2')); 2.43 (t, J 6.4, 1 H, OCH2CH2CN);
2.28 ± 2.35 (m, 1 H, HÀC(2')); 1.17± 1.19 ( m, 9 H, 2 Me2CH); 1.06 (d, J 6.8, 3 H, 2 Me2CH). 13C-NMR
(100 MHz, CDCl3): 162.43 (s, C(4)); 158.61 (s, arom. C); 150.11, 150.05 (2s, C(2)); 144.40 (s, arom. C); 138.47
(d, C(6)); 137.86, 135.44, 135.32, 135.27 (4s, arom. C); 130.14, 130.10, 128.22, 128.18, 128.10, 127.94, 127.70,
127.48, 127.03, 127.00 (10d, arom. C); 117.51, 117.32 (2s, CN); 113.20 (d, arom. C); 112.22, 112.16 (2s, C(5)); 86.75
(s, CÀOÀC(5')); 85.56, 85.34, 84.88, 84.84 (4d, C(1'), C(4')); 73.65 (dd, J(C,P) 17.5, C(3')); 73.19
(dd, J(C,P) 16.8, C(3')); 72.81 (t, PhCH2); 64.19 (t, CH2ÀC(5)); 63.08, 62.87(2 t, C(5')); 58.26, 58.15
(2dt, J(C,P) 18.9, OCH2CH2CN); 55.17, 55.16 (2q, MeO); 43.24 (dd, J(C,P) 12.1, Me2CH); 43.13
(dd, J(C,P) 9.1, Me2CH); 40.05 (d, C(2')); 24.60, 24.53, 24.48, 24.40 (4q, Me2CH); 20.34, 20.13
(2dt, J(C,P) 7.1, OCH CH2CN). 31P-NMR (162 MHz, CDCl3): 157.93, 157.45. LSI-MS: no MH , 336 (8),
2
304 (24), 303 (100), 232 (5), 228 (7), 105 (6).
N4-Benzoyl-5-[(benzyloxy)methyl]-2'-deoxy-5'-O-(4,4'-dimethoxytrityl)cytidine 3'-(2-Cyanoethyl Diisopro-
pylphosphoramidite) (19). Rf 0.54, 0.46 (hexane/AcOEt 1:1). UV (EtOH): 234 (28780), 263 sh (12490), 327
(22660). IR (KBr): 3436w (br.), 3064w, 3031w, 2966m, 2930m, 2869m, 2837w, 2252w, 1711s, 1648m, 1599m,
1570s, 1508s, 1488m, 1463m, 1448m, 1396w, 1364m, 1334m, 1310m, 1276s, 1251s, 1200m, 1179s, 1156w, 1084m,