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E. M. Zubin et al. / Bioorg. Med. Chem. 13 (2005) 4912–4920
75 ! 100% CHCl3 in benzene, v/v) to give compound 5,
which was obtained as a white solid (1.24 g, 87.4%). Rf
0.64 (CHCl3/MeOH, 98:2 v/v). MALDI-TOF (2,4,6-
THAP): [M+H]+ calcd 817.06, found 816.64; [M+Na]+
calcd 839.04, found 838.38; [M+K]+ calcd 855.15, found
854.53. 1H NMR (500.13 MHz, CDCl3): d 7.82 (dd, 1H,
171.13, 171.03 (CH3C@O), 169.99 (OCH2CO), 161.66
(C-4), 150.47 (C-2), 139.29 (C-6), 101.62 (C-5), 89.39
(C-10), 84.26, 83.84 (C-20, C-40), 70.45 (CH(OAc)-
CH2(OAc)), 69.91 (OCH2CO), 68.35 (C-30), 64.48
(CH2OCOtBu), 62.94 (CH(OAc)CH2(OAc)), 60.53 (C-
50), 39.31 (CONHCH2), 38.87 (C(CH3)3), 27.00
(C(CH3)3), 20.99, 20.75 (CH3CO).
J5,6 = 8.2, H-6), 7.22 (dd, 1H, JNH,CH = 13.0, 6.5,
2
CONHCH2), 5.96 (d, 1H, Jgem = 8.8, CH2OCOtBu),
5.90 (d, 1H, Jgem = 8.8, CH2OCOtBu), 5.79 (br s, 1H,
H-10), 5.72 (d, 1H, J5,6 = 8.2, H-5), 5.18 (m, 1H,
CH(OAc)CH2(OAc)), 4.35 (d, 1H, Jgem = 16.5, OCH2-
CO), 4.30 (d, 1H, Jgem = 16.5, OCH2CO), 4.28 (m, 2H,
3.7. 20-O-[2-(2,3-Diacetoxypropyl)amino-2-oxoethyl]-50-
O-(4,40-dimethoxytrityl)-N3-pivaloyloxymethyl uridine
(7)
CH(OAc)CH2(OAc), H-50a), 4.22 (dd, 1H, J2 ,3 = 3.5,
Compound 6 (0.77 g, 1.34 mmol) was co-evaporated
with pyridine (3· 20 ml), dissolved in dry pyridine
(25 ml) and cooled in an ice bath, and DMTrCl
(0.73 g, 2.14 mmol) was added in one portion. The reac-
tion was monitored by TLC until the starting nucleoside
disappeared. After completion of the reaction, excess of
DMTrCl was quenched with MeOH (1 ml), and after
10 min the mixture was evaporated two-thirds, diluted
with CHCl3 (50 ml), washed with 5% NaHCO3 (2·
50 ml) and 20% NaCl (50 ml) and then dried (Na2SO4),
evaporated and co-evaporated with toluene (3· 25 ml)
and the residue was chromatographed on silica gel
column (stepwise gradient of 0 ! 20 ! 25 ! 30 !
50 ! 100% CHCl3 in toluene and further 1% MeOH
in CHCl3 + 1% pyridine v/v/v). Yield 0.99 g (84.3%).
Rf 0.25 (CHCl3/MeOH, 98:2 v/v). MALDI-TOF
(2,4,6-THAP): [M+Na]+ calcd 898.9, found 899.21;
[M+K]+ calcd 915.01, found 915.16. 1H NMR
(500.13 MHz, CDCl3): d 8.05 (dd, 1H, J5,6 = 8.0, H-6),
7.40 (d, 2H, J = 7.8, o-Ph), 7.30 (d, 2H, J = 8.5, o-An),
7.25 (m, 4H, m,p-Ph, CONHCH2), 6.80 (d, 2H,
J = 8.5, m-An), 5.90 (m, 2H, CH2OCOtBu), 5.85 (over-
lap, 1H, H-10), 5.30 (d, 1H, J5,6 = 8.0, H-5), 5.10 (m,
1H, CH(OAc)CH2(OAc)), 4.50 (app q, 1H, J = 6.5, H-
30), 4.42 (d, 1H, Jgem = 15.8, OCH2CO), 4.36 (d, 1H,
Jgem = 15.8, OCH2CO), 4.25 (m, 1H, CH(OAc)-
CH2(OAc)), 4.15 (m, 1H, CH(OAc)CH2(OAc)), 4.10
0
0
J3 ,4 = 8.5, H-30), 4.15 (m, 2H, CH(OAc)CH2(OAc),
0
0
H-40), 3.98 (d, 1H, Jgem = 13.0, J4 ,5 b = 2.3, H-50b),
3.86 (app t, 1H, J = 4.0, H-20), 3.63 (m, 1H,
CONHCH2), 3.50 (m, 1H, CONHCH2), 2.10, 2.07 (2s,
0
0
t
each 3H, CH3CO), 1.20 (s, 9H, Bu), 1.10–0.80 (m,
i
28H, Pr). 13C NMR (75.47 MHz, CDCl3): d 177.24
(CH2OCOtBu), 170.61, 169.72 (CH3C@O), 161.41
(C-4), 150.28 (C-2), 137.57 (C-6), 101.44 (C-5), 89.43
(C-10), 83.09 (C-20), 81.64 (C-40), 70.52 (CH(OAc)-
CH2(OAc)), 70.32 (OCH2CO), 68.91 (C-30), 64.33
(CH2OCOtBu), 63.03 (CH(OAc)CH2(OAc)), 59.12
(C-50), 39.38 (C(CH3)3), 38.91 (CONHCH2), 26.99
(C(CH3)3), 20.94, 20.72 (CH3CO), 17.44, 17.37, 17.00,
16.86 (CH(CH3)2), 13.38, 13.02, 12.89, 12.71
(CH(CH3)2).
3.6. 20-O-[2-(2,3-Diacetoxypropyl)amino-2-oxoethyl]-N3-
pivaloyloxymethyluridine (6)
To a solution of 5 (1.21 g, 1.48 mmol) in THF (5 ml) in a
screw-top Teflon flask (Nalgene) equipped with a mag-
netic stirring bar was added triethylamine trihydrofluo-
ride (0.48 ml, 2.96 mmol) and the mixture was left
stirring for 1.5 h at ambient temperature. The comple-
tion of deprotection was checked by TLC (CHCl3/
MeOH, 96:4 v/v) and then the mixture was diluted with
EtOAc (50 ml), washed with 5% NaHCO3 (2· 50 ml),
water (50 ml), 5% citric acid (2· 50 ml), and 20% NaCl
(50 ml) and then dried (Na2SO4) and evaporated to dry-
ness. The residue was co-evaporated with CHCl3 (3·
25 ml) and then chromatographed on silica gel column
(stepwise gradient of 0 ! 1 ! 2 ! 3 ! 4% MeOH in
CHCl3, v/v). Yield 0.81 g (95.3%). Rf 0.26 (CHCl3/
MeOH, 92:8 v/v). MALDI-TOF (2,4,6-THAP):
[M+H]+ calcd 574.55, found 574.75; [M+Na]+ calcd
596.54, found 591.44; [M+K]+ calcd 612.64, found
612.28. 1H NMR (500.13 MHz, CDCl3): d 8.05 (dd,
1H, J5,6 = 8.3, H-6), 7.40 (br s, 1H, CONHCH2), 5.96
(d, 1H, Jgem = 9.5, CH2OCOtBu), 5.90 (d, 1H,
Jgem = 9.5, CH2OCOtBu), 5.85 (app t, 1H, J = 2.8,
H-10), 5.80 (d, 1H, J5,6 = 8.0, H-5), 5.10 (m, 1H,
CH(OAc)CH2(OAc)), 4.38 (d, 1H, Jgem = 16.6, OCH2-
CO), 4.32 (m, 1H, H-30), 4.30 (d, 1H, Jgem = 16.6,
OCH2CO), 4.25 (m, 1H, H-40), 4.20 (m, 1H, CH(OAc)-
CH2(OAc)), 4.10 (m, 1H, CH(OAc)CH2(OAc)), 4.04 (d,
1H, Jgem = 12.0, H-50a), 4.02 (m, 1H, H-20), 3.90 (d, 1H,
Jgem = 12.0, H-50b), 3.6 (m, 1H, CONHCH2), 3.45 (m,
1H, CONHCH2), 3.25 (br s, 1H, OH), 2.10 (br s, 1H,
(app q, 1H, J = 6.5, H-40), 3.90 (dd, 1H, J1 ,2 = 4.5,
0
0
J2 ,3 = 13.0, H-20), 3.80 (s, 3H, OCH3), 3.70 (m, 1H,
30-OH), 3.65 (m, 1H, CONHCH2), 3.55 (m, 2H, H-50),
3.40 (m, 1H, CONHCH2), 2.10 (s, 6H, CH3CO), 1.20
0
0
t
(s, 9H, Bu). 13C NMR (62.90 MHz, CDCl3): d 177.80
(CH2OCOtBu), 171.10, 171.00 (CH3C@O), 169.50
(OCH2CO), 161.45 (C-4), 158.82 (p-An), 150.20 (C-2),
144.50 (i-Ph), 138.48 (C-6), 135.31, 135.11 (i-An),
130.16 (o-An), 128.17, 128.09 (m,o-Ph), 127.26 (p-Ph),
113.40 (m-An), 101.65 (C-5), 88.70 (C-10), 87.10
(C(Ar)3), 84.16 (C-20), 82.80 (C-40), 70.59 (CH(OAc)-
CH2(OAc)), 69.96 (OCH2CO), 68.60 (C-30), 64.00
(CH(OAc)CH2(OAc)), 60.00 (C-50), 55.30 (OCH3),
39.49 (CONHCH2), 39.40 (C(CH3)3), 27.05 (C(CH3)3),
21.01, 20.77 (CH3CO).
3.8. 20-O-[2-(2,3-Diacetoxypropyl)amino-2-oxoethyl]-30-
O-(N,N-diisopropylamino-2-cyanoethoxy phosphinyl)-50-
O-(4,40-dimethoxytrityl)-N3-pivaloyloxymethyluridine (8)
Compound 7 (0.95 g, 1.09 mmol) was co-evaporated
with dry CH2Cl2 (3· 20 ml), dissolved in dry CH2Cl2,
diisopropylammonium tetrazolide (0.28 g, 1.63 mmol)
t
OH), 2.05 (m, 6H, CH3CO), 1.20 (s, 9H, Bu). 13C
NMR (75.47 MHz, CDCl3): d 177.58 (CH2OCOtBu),
and
bis(N,N-diisopropylamino)-2-cyanoethoxyphos-