A R T I C L E S
Ve´liz and Beal
spectra were obtained on a Finnigan Mat 95. N-(dimethylacetamidine)-
5′-O-DMT-8-azaadenosine (1),33 8-azaadenosine (4),33 2′,3′,5′-tri-O-
acetyl 6-bromonebularine (8),34 and 2′,3′,5′-tri-O-acetyl-8-azaadenosine
(17)33 were synthesized according to literature procedures.
of TBDMSCl (1.1 equiv). After 5 min, AgNO3 (1.1 equiv) was added
to the solution. After 8 h of stirring at room temperature, the reaction
mixture was diluted with EtOAc (25 mL), filtered, and washed with
5% aqueous NaHCO3 (1 × 30 mL). The organic layer was dried (Na2-
SO4), filtered, and concentrated under reduced pressure. The crude
products were purified by flash column chromatography on silica gel
using appropriate solvent systems (listed under individual compound
headings, vide infra).
Procedure for the Preparation of 8-Azainosine (5). ADA (19.5
mg; Sigma, 2.2 units/mg protein, calf intestinal mucosa) was added to
a solution of 4 (430 mg, 1.60 mmol) in aqueous sodium phosphate
buffer (0.1 M, 39 mL; pH 7.4) and stirring was continued at room
temperature overnight. The reaction mixture was concentrated under
reduced pressure and the residue was purified by flash column
chromatography (10-20% MeOH/CHCl3) to afford 5 (369.8 mg, 86%)
as a white solid. Spectroscopic data agreed with reported values.52
General Procedure for the Preparation of N6-Substituted Ad-
enosine Analogues. The amine (10 equiv.) was added to a solution of
the 6-bromonebularine triacetate (0.656-1.09 mmol) in MeOH (10 mL).
The reaction mixture was stirred at room temperature for 8h. It was
concentrated under reduced pressure and the solid was triturated with
EtOAc to obtained the respective N6-substituted product (vide infra).
N6-Methyladenosine (9). White solid (94%). Spectroscopic data
agreed with reported values.53
N-(Dimethylacetamidine)-5′-O-(4,4′-dimethoxytrityl)-2′-O-(t-bu-
tyldimethyl-silyl)-8-azaadenosine (2). Chromatography, EtOAc/hex-
1
anes 4:1. White foam (30%). H NMR (CD2Cl2, 300 MHz): δ (ppm)
8.57 (s, 1H), 7.47 (dd, J ) 8.1, 1.8 Hz, 2H), 7.35 (dd, J ) 6.3, 2.7 Hz,
4H), 7.27-7.19 (m, 3H), 6.79 (d, J ) 7.5 Hz, 4H), 6.40 (d, J ) 4.5
Hz, 1H), 5.36 (t, J ) 5.1 Hz, 1H), 4.48 (q, J ) 4.5 Hz, 1H), 4.27 (q,
J ) 4.8 Hz, 1H), 3.78 (s, 6H), 3.43 (dd, J ) 10.5, 3.6 Hz, 1H), 3.30
(s, 3H), 3.26 (dd, J ) 10.5, 5.1 Hz, 1H), 3.21 (s, 3H), 2.76 (d, J ) 4.8
Hz, 1H), 2.30 (s, 3H), 0.87 (s, 9H), 0.05 (s, 3H), -0.11 (s, 3H). 13C
NMR (CD2Cl2, 75 MHz): δ (ppm) 164.7, 161.0, 159.1, 157.5, 151.0,
145.6, 136.6, 136.4, 130.6, 128.7, 128.2, 127.1, 113.5, 89.9, 86.7, 85.1,
75.1, 72.4, 64.4, 55.7, 39.3, 38.9, 25.9, 18.4, 18.1, -4.7, -4.8.
HRFABMS: calcd for C40H52N7O6Si (M + H)+ 754.3748, obsd
754.3708.
N6-Ethyladenosine (10). White solid (99%). Spectroscopic data
agreed with reported values.54
General Procedure for the Preparation of 5′-O-(4,4′-dimethoxy-
trityl)-N6-Substituted Adenosine Analogues and 8-Azainosine. To
a solution of the ribonucleoside (0.615-1.68 mmol) in freshly distilled
THF (15 mL) was added sequentially anhydrous pyridine (6.0 equiv.),
4,4′-dimethoxytrityl chloride (1.1 equiv), and AgNO3 (1.1 equiv). The
reaction mixture was stirred at room temperature overnight. The mixture
was diluted with EtOAc (25 mL), filtered, and washed with 5% aqueous
NaHCO3 (1 × 40 mL) and brine (1 × 30 mL). The organic layer was
dried (Na2SO4), filtered, and concentrated under reduced pressure. The
crude products were purified by flash column chromatography (DCM/
MeOH/TEA 98:1:1), except for the 8-azainosine derivative which was
coevaporated with toluene to remove pyridine and used without
purification.
5′-O-(4,4′-Dimethoxytrityl)-2′-O-(t-butyldimethylsilyl)-8-aza-
inosine (6). Chromatography, EtOAc/hexanes 5:1. White foam (30%).
1H NMR (CD2Cl2, 300 MHz): δ (ppm) 8.34 (s, 1H), 7.47 (d, J ) 6.9
Hz, 2H), 7.35 (d, J ) 7.8 Hz, 4H), 7.29-7.21 (m, 3H), 6.81 (d, J )
8.4 Hz, 4H), 6.37 (d, J ) 4.5 Hz, 1H), 5.23 (t, J ) 4.8 Hz, 1H), 4.47
(t, J ) 4.5 Hz, 1H), 4.31 (q, J ) 3.3 Hz, 1H), 3.45 (dd, J ) 10.5, 3.3
Hz, 1H), 3.31 (dd, J ) 10.5, 5.4 Hz, 1H), 2.71 (br s, 1H), 3.77 (s, 6H),
0.89 (s, 9H), 0.07 (s, 3H), -0.06 (s, 3H). 13C NMR (CD2Cl2, 75
MHz): δ (ppm) 159.1 157.7, 150.2, 149.4, 145.5, 136.5, 136.3, 130.6,
128.7, 128.3, 127.3, 113.6, 90.2, 86.8, 85.5, 75.6, 72.4, 64.2, 55.7, 25.9,
18.4, -4.7, -4.8. HRFABMS: calcd for C36H43N5O7Si M+ 685.2932,
obsd 685.2949.
5′-O-(4,4′-Dimethoxytrityl)-2′-O-(t-butyldimethylsilyl)-N6-methyl-
5′-O-(4,4′-Dimethoxytrityl)-N6-methyladenosine (11). Light orange
adenosine (13). Chromatography, 20-40% EtOAc/hexanes. White
1
1
foam (62%). H NMR (CD2Cl2, 300 MHz): δ (ppm) 8.29 (br s, 1H),
foam (37%). H NMR (CD2Cl2, 300 MHz): δ (ppm) 8.28 (br s, 1H),
8.00 (s, 1H), 7.31-7.27 (m, 2H), 7.21-7.16 (m, 5H), 6.73 (dd, J ) 9,
3.9 Hz, 4H), 6.03 (br s, 1H), 5.95 (d, J ) 6 Hz, 1H), 4.77 (t, J ) 5.1
Hz, 1H), 4.39-4.35 (m, 2H), 3.75 (s, 3H), 3.74 (s, 3H), 3.41 (dd, J )
7.98 (s, 1H), 7.48 (d, J ) 7.2 Hz, 2H), 7.34 (d, J ) 8.7 Hz, 4H),
7.31-7.20 (m, 3H), 6.83 (d, J ) 9 Hz, 4H), 6.40 (br s, 1H), 6.01 (d,
J ) 5.1 Hz, 1H), 5.04 (t, J ) 5.1 Hz, 1H), 4.37 (br s, 1H), 4.24 (q, J
) 3.9 Hz, 1H), 3.77 (s, 6H), 3.50 (dd, J ) 10.5, 4.2 Hz, 1H), 3.15 (br
s, 3H), 2.83 (br s, 1H), 0.86 (s, 9H), 0.01 (s, 3H), -0.10 (s, 3H). 13C
NMR (CD2Cl2, 75 MHz): δ (ppm) 159.2, 156.0, 153.8, 145.4, 139.1,
136.3, 130.6, 130.6, 128.7, 128.4, 127.4, 120.8, 113.7, 89.0, 87.0, 84.5,
75.9, 72.0, 64.0, 55.7, 30.2, 25.9, 18.4, -4.7, -4.9. HRFABMS: calcd
for C38H46N5O6Si (M - H)+ 696.3217, obsd 696.3197.
10.5, 3.6 Hz, 1H), 3.23 (dd, J ) 10.5, 3.6 Hz, 1H), 3.16 (br s, 3H). 13
C
NMR (CD2Cl2, 75 MHz): δ (ppm) 159.2, 153.1, 145.1, 138.5, 136.2,
136.0, 130.5, 130.4, 128.5, 128.3, 127.3, 113.6, 91.3, 87.0, 86.7, 76.5,
73.3, 64.2, 55.7, 54.8, 53.3, 30.4. HRFABMS: calcd for C32H34N5O6
(M + H)+ 584.2509, obsd 584.2525.
5′-O-(4,4′-Dimethoxytrityl)-N6-Ethyladenosine (12). Light orange
1
5′-O-(4,4′-Dimethoxytrityl)-2′-O-(t-butyldimethylsilyl)-N6-ethylad-
enosine (14). Chromatography, 30% EtOAc/hexanes. White foam
(40%). Equilibration of the 3′-O-TBDMS derivative in 0.1% TEA/
MeOH for 8h, followed by purification (chromatography, 30% EtOAc/
foam (60%). H NMR (CD2Cl2, 300 MHz): δ (ppm) 8.22 (br s, 1H),
8.05 (s, 1H), 7.39 (app. d, J ) 6.9 Hz, 2H), 7.30-7.17 (m, 7H), 6.78
(dd, J ) 8.7, 2.1 Hz, 4H), 6.45 (br s, 1H), 6.09 (d, J ) 5.1 Hz, 1H),
4.82, (t, J ) 5.1 Hz, 1H), 4.48 (t, J ) 4.8 Hz, 1H), 4.38 (q, J ) 3.3
Hz, 1H), 3.74 (s, 6H), 3.62 (br s, 2H), 3.45 (dd, J ) 10.2, 3.0 Hz, 1H),
3.34 (dd, J ) 10.5, 3.9 Hz, 1H), 1.27 (t, J ) 7.5 Hz, 3H). 13C NMR
(CD2Cl2, 75 MHz): δ (ppm) 159.0, 155.2, 153.2, 145.2, 138.6, 136.1,
136.1, 130.5, 128.5, 128.3, 127.3, 120.2, 113.5, 90.2, 86.9, 85.6, 75.9,
72.3, 64.1, 55.6, 36.0, 15.1. HRFABMS: calcd for C33H36N5O6 (M +
H)+ 598.2666, obsd 598.2647.
General Procedure for the Preparation of 5′-O-(4,4′-Dimethoxy-
trityl)-2′-O-(t-butyldimethylsilyl)-N6-Substituted Adenosine Ana-
logues, 8-Azaadenosine, and 8-Azainosine. The 5′-O-DMT derivative
(0.377-0.742 mmol) was dissolved in freshly distilled THF (15 mL)
and to this was added triethylamine (1.9 equiv), followed by the addition
1
hexanes) afforded 25% of the product. Total yield: 65%. H NMR
(CD2Cl2, 300 MHz): δ (ppm) 8.25 (br s, 1H), 7.95 (s, 1H), 7.49 (dd,
J ) 8.1, 1.5 Hz, 2H), 7.37 (d, J ) 8.7 Hz, 4H), 7.32-7.23 (m, 3H),
6.83 (d, J ) 8.7 Hz, 4H), 6.07 (br s, 1H), 6.00 (d, J ) 5.1 Hz, 1H),
5.05 (t, J ) 5.1 Hz, 1H), 4.38 (br s, 1H), 4.24 (q, J ) 3.6 Hz, 1H),
3.78 (s, 6H), 3.66 (br s, 2H), 3.49 (dd, J ) 10.5, 3.3 Hz, 1H), 3.39
(dd, J ) 10.5, 4.5 Hz, 1H), 2.87 (br s, 1H), 1.29 (t, J ) 6 Hz, 3H),
0.86 (s, 9H), 0.01 (s, 3H), -0.10 (s, 3H). 13C NMR (CD2Cl2, 75
MHz): δ (ppm) 159.2, 155.4, 153.7, 145.4, 139.1, 136.3, 130.6, 130.6,
128.6, 128.4, 127.4, 120.7, 113.6, 89.0, 84.5, 75.8, 72.0, 64.1, 55.7,
36.0, 25.9, 18.3, 15.3, -4.7, -4.9. HRFABMS: calcd for C39H50N5O6-
Si (M + H)+ 712.3530, obsd 712.3536.
General Procedure for the Preparation of 5′-O-(4,4′-Dimeth-
oxytrityl)-3′-O-[(2-cyanoethoxy)(N,N-diisopropylamino)phosphino]-2′-
O-(t-butyldimethylsilyl)-N6-substituted Adenosine Analogues, 8-Aza-
adenosine, and 8-Azainosine. The phosphoramidite formation was
performed according to standard procedure on the 5′-O-DMT-2′-O-
(52) Hutzenlaub, W.; Tolman, R. L.; Robins, R. K. J. Med. Chem. 1972, 15,
879-883.
(53) Mikkola, S.; Koissi, N.; Ketoma¨ki, K.; Rauvala, S.; Neuvonen, K.;
Lo¨nnberg, H. Eur. J. Org. Chem. 2000, 2315-2323.
(54) Bressi, J. C.; Choe, J.; Hough, M. T.; Buckner, F. S.; van Voorhis, W. C.;
Verlinde, C. L. M. J.; Hol, W. G.; Gelb, M. H. J. Med. Chem. 2000, 43,
4135-4150.
9
10874 J. AM. CHEM. SOC. VOL. 125, NO. 36, 2003