Petersen and Rajski
with a 10% citric acid solution, water, sodium bicarbonate, and
then brine, dried over sodium sulfate, and evaporated to give
an off-white solid. Trituration of the crude solid with diethyl
ether afforded 3.5 g of pure 5′-amino-5′-deoxy-2′,3′-bis(O-
triethylsilyl)adenosine as a white powder in 86% yield: mp
153.5-155 °C; 1H NMR (400 MHz, CDCl3) δ 8.12 (1H, s), 8.08
(1H, s), 6.64 (2H, s), 5.89 (1H, d, J ) 5.9 Hz), 5.25 (1H, dd, J
) 6.0, 4.24 Hz), 4.40-4.30 (2H, m), 4.23 (1H, dd, J ) 14.1, 6.6
Hz), 3.94 (1H, dd, J ) 14.2, 6.2 Hz), 0.93 (9H, t, J ) 8.0 Hz),
0.80 (9H, t, J ) 7.9 Hz), 0.61 (6H, q, J ) 7.9 Hz), 0.41 (3H,
decet, J ) 8.0 Hz), 0.37 (3H, decet, J ) 7.8 Hz) ppm; 13C NMR
(100 MHz, CDCl3) δ 168.4, 155.5, 152.0, 149.8, 141.2, 134.4,
132.2, 123.6, 120.7, 89.3, 83.3, 74.2, 73.6, 69.1, 6.9, 6.7, 6.1,
5.1, 4.6 ppm; m/z 214 (M+, 100); HRMALDI calcd for
C30H45N6O5Si2 (M + H)+ 625.2990, found 625.2910.
h. The mixture was filtered, washed with saturated NaHCO3,
water, and then brine, and evaporated. The product was
recrystallized from MeOH/hexanes to give pure 9 in 62% yield.
Product retained in the mother liquor was isolated by column
chromatography. Conditions: 2.5 L of a 1:1 mixture of DCM/
EtOAc was used to elute all byproducts. Product started to
elute after passage of 300 mL of 4.5:4.5:1 DCM/EtOAc/MeOH
and was collected in the following 1.5 L. Collected fractions
and recrystallized compound were evaporated to give 3.86 g
1
of product in 73% overall yield: mp 178.5-180 °C; H NMR
(500 MHz, CDCl3) δ 8.20 (1H, s), 8.00(1H, s), 7.92 (1H, dd, J
) 8.1, 1.1 Hz), 7.80 (1H, dd, J ) 8.1, 1.1 Hz), 7.73 (1H, dt, J
) 7.7, 0.7 Hz), 7.65 (1H, dt, J ) 7.7, 0.7 Hz), 6.11 (1H, d, J )
2.2 Hz), 5.36 (1H, dd, J ) 6.2, 2.2 Hz), 4.94 (1H, dd, J ) 6.2,
1.9 Hz), 4.28-4.24 (1H, m), 4.03 (1H, d, 18.7 Hz), 3.78-3.64
(4H, m), 3.52 (1H, dd, J ) 15.38, 9.15 Hz), 3.23 (1H, s), 1.42
(3H, s), 1.21 (3H, s) 0.85 (3H, t, J ) 7.3 Hz) ppm; 13C NMR
(125 MHz, d6-DMSO) δ 168.6, 156.9, 153.4, 149.0, 148.0, 141.1,
135.3, 132.9, 132.2, 131.0, 124.8, 120.0, 114.0, 90.3, 86.6, 83.6,
82.6, 61.4, 50.3, 49.7, 27.6, 25.8, 14.3 ppm; m/z 214 (M+, 100);
HRMALDI calcd for C23H27O9N7S (M + H)+ 578.1669, found
578.1631.
5′-Amino Glycyl Ethyl Ester 5′-Deoxy-2′,3′-Bis(O-tri-
ethylsilyl)adenosine (6) [Mitsunobu Method]. To a stir-
ring 10:1 TFA/water mixture at 0 °C was added 9 (1.15 g, 2
mmol) portion-wise. The reaction was stirred until complete
disappearance of starting material, which was observed at 3.5
h. The resulting suspension was evaporated in vacuo followed
by three coevaporations with anhydrous EtOH to remove all
traces of TFA. Crude 6 precursor was triturated with water
and then CHCl3 to afford 990 mg of diol in 92% yield. Crude
precursor to 6 (950 mg, 1.77 mmol) and TEA (1.5 mL, 10.8
mmol) were dissolved in THF and cooled to 0 °C. Et3SiCl (1.07
mL, 6.4 mmol) was added dropwise and the reaction stirred
for 8 h. The resulting crude reaction contents were filtered,
evaporated, and redissolved in 50 mL of EtOAc. The organic
portion was washed with saturated NaHCO3, water, and brine,
dried over Na2SO4, and evaporated. Silica chromatography (8:
4:1 Hex/EtOAc/MeOH) afforded 1.04 g of di-TES-protected
compound in 77% yield: mp 158-160 °C; 1H NMR (400 MHz,
CDCl3) δ 8.23 (1H, s), 8.05(1H, d, J ) 7.98 Hz), 7.81 (1H, s),
7.68-7.57(3H, m), 5.79 (1H, d, J ) 6.5 Hz), 5.60 (2H, br), 5.27
(1H, dd, J ) 6.5, 4.4 Hz), 4.31-4.28 (1H, m), 4.27-4.24 (2H,
m), 4.16 (1H, d, 18.7 Hz), 4.08-4.0 (2H, m), 3.98-3.90 (1H,
m), 3.84 (1H, dd, J ) 15.1, 9.3 Hz), 1.26 (1H, s), 1.1 (3H, t, J
) 7.1 Hz) 0.99 (9H, t, J ) 7.9 Hz), 0.75 (9H, t, J ) 7.9 Hz),
0.67 (6H, q, J ) 7.9 Hz), 0.35 (3H, decet, J ) 7.7 Hz), 0.28
(3H, decet, J ) 7.7 Hz) ppm; 13C NMR (100 MHz, CDCl3) δ
169.1, 158.6, 152.8, 150.1, 150.1, 141.0, 133.6, 131.7, 131.1,
127.9, 124.2, 90.1, 86.0, 74.3, 72.6, 61.4, 50.6, 49.8, 14.1, 7.1,
6.6, 5.1, 4.4 ppm; m/z 214 (M+, 100); HRMALDI calcd for
C32H51O9N7SSi2 (M + Na)+ 788.2905, found 788.2860.
To 577 mg (0.753 mmol) of silyl ether was added K2CO3 (312
mg, 2.26 mmol) and 50 mL DMF. To the stirring solution was
added thiophenol (92 µL, 0.904 nmol) dropwise. The mixture
was stirred for 12 h. The crude mixture was filtered and
evaporated. The resulting yellow oil was resuspended in 4 mL
of CH2Cl2 and extracted with saturated NaHCO3. The organic
layer was subsequently chromatographed using 100% DCM
until all traces of a UV-active yellow band had eluted. The
eluent was then changed to 85% CH2Cl2/MeOH, which facili-
tated isolation of 428 mg of 6 at 98% yield: mp 119-121.5 °C;
1H NMR (400 MHz, CDCl3) δ 8.34 (1H, s), 7.95(1H, s), 6.27
(2H, br), 5.86 (1H, d, J ) 6.2 Hz), 5.10 (1H, dd, J ) 6.0, 4.5
Hz), 4.26 (1H, dd, J ) 4.4, 2.9 Hz), 4.16 (2H, q, 7.2 Hz), 4.15
(1H, d, 10.3 Hz), 3.44 (2H, s), 2.99 (1H, dd, J ) 12.5, 3.2 Hz),
2.88 (1H, dd, J ) 12.5, 6.2 Hz), 2.84-2.76 (1H, br), 1.23 (3H,
t, J ) 7.0 Hz) 0.97 (9H, t, J ) 7.9 Hz), 0.76 (9H, t, J ) 7.9 Hz),
0.64 (6H, q, J ) 7.8 Hz), 0.41 (3H, decet, J ) 8.0 Hz), 0.39
(3H, decet, J ) 7.8 Hz) ppm; 13C NMR (100 MHz, CDCl3) δ
172.4, 155.8, 153.1, 150.1, 141.1, 121.1, 89.8, 85.6, 74.1, 74.1,
5′-Phthalimide-5′-deoxy-2′,3′-bis(O-triethylsilyl)adenosine (625
mg, 1.0 mmol) and a 16-fold excess of hydrazine hydrate were
dissolved in 30 mL of ethanol and gently refluxed overnight.
The obtained solution was allowed to cool to room temperature
and then filtered. The filtrate was evaporated to dryness in
vacuo. The residue was treated with 5 mL of water; glacial
acetic acid was added to achieve pH 4, and the mixture was
then filtered. The filtrate was adjusted to pH 10 with aqueous
4 N NaOH. Extraction with chloroform, drying of the combined
organic layers with MgSO4, and removal of the solvents by
evaporation gave the 353 mg of amino adenylate 5 at 72%:
1
mp 164-166.5 °C; H NMR (400 MHz, CDCl3) δ 8.34 (1H, s),
7.94(1H, s), 6.12-5.84 (2H, br), 5.86 (1H, d, J ) 6.0 Hz), 5.11
(1H, dd, J ) 6.0, 4.8 Hz), 4.29 (1H, dd, J ) 4.0, 2.8 Hz), 4.12-
4.08 (1H, m), 3.14 (1H, dd, J ) 13.6, 3.2 Hz), 3.02 (1H, dd, J
) 13.2, 5.6 Hz), 1.80 (2H, s, br), 1.00 (9H, t, J ) 7.8 Hz), 0.78
(9H, t, J ) 7.8 Hz), 0.67 (6H, q, J ) 7.8 Hz), 0.41 (3H, decet,
J ) 8.0 Hz), 0.37 (3H, decet, J ) 7.8 Hz) ppm; 13C NMR (100
MHz, CDCl3) δ 156.2, 153.6, 150.1, 141.1, 121.0, 90.0, 74.0,
73.8, 44.0, 7.2, 6.9, 5.8, 5.5 ppm; m/z 214 (M+, 100); HRMALDI
calcd for C22H42O3N6Si2 (M + H)+ 495.2935, found 495.2943.
5′-Amino Glycyl Ethyl Ester-5′-deoxy-2′,3′-bis(O-tri-
ethylsilyl)adenosine(6)[BromoacetateAlkylationMethod].
To 5 (4.95 g, 10.0 mmol) was added Et3N (4.5 mL, 32 mmol)
and 20 mL of anhydrous THF at 0 °C. Ethylbromoacetate (1.12
mL, 10 mmol) was added dropwise to the stirring solution and
allowed to warm to room-temperature overnight. The resulting
mixture was filtered to remove the triethylamine hydrobro-
mide salt and evaporated. The resulting oil was diluted with
diethyl ether to precipitate unreacted starting material, and
the filtrate was evaporated. The crude material was dissolved
in ethanol on ∼100 mL of silica and evaporated. The dried
powder was added to a flash column containing wet packed
silica 4:4:0.5 CH2Cl2/EtOAc/MeOH. The non-UV-active initial
fractions were discarded, and the first 100 mL of UV-active
eluant was discarded (removing dialkylated contaminant).
Fractions were collected until UV activity disappeared, and
solvent was evaporated, giving 5.08 g of product 6 in 92%
yield: mp 117-121 °C; 1H NMR (400 MHz, CDCl3) δ 8.34 (1H,
s), 7.95(1H, s), 6.27 (2H, br), 5.86 (1H, d, J ) 6.2 Hz), 5.10
(1H, dd, J ) 6.0, 4.5 Hz), 4.26 (1H, dd, J ) 4.4, 2.9 Hz), 4.16
(2H, q, 7.2 Hz),4.15 (1H, d, 10.3 Hz), 3.44 (2H, s), 2.99 (1H,
dd, J ) 12.5, 3.2 Hz), 2.88 (1H, dd, J ) 12.5, 6.2 Hz), 2.84-
2.76 (1H, br), 1.23 (3H, t, J ) 7.0 Hz) 0.97 (9H, t, J ) 7.9 Hz),
0.76 (9H, t, J ) 7.9 Hz), 0.64 (6H, q, J ) 7.8 Hz), 0.41 (3H,
decet, J ) 8.0 Hz), 0.39 (3H, decet, J ) 7.8 Hz) ppm; 13C NMR
(100 MHz, CDCl3) δ 172.5, 156.1, 153.1, 149.9, 140.9, 121.0,
89.7, 85.6, 74.2, 74.1, 60.9, 51.5, 51.1, 14.4, 7.05, 6.7, 5.1, 4.7
ppm; m/z 214 (M+, 100); HRMALDI calcd for C26H48O5N6Si2
(M + H)+ 603.3122, found 603.3081.
5′-o-Nitrobenzenesulfonyl-N-glycyl Ethyl Ester 2′,3′-
O-Isopropylidene Adenosine (9). 2′,3′-Isopropylidene-
adenosine (3.07 g, 10.0 mmol), triphenylphosphine (3.15 g, 12
mmol), and nosylated glycine ethyl ester 8 (3.46 g, 12 mmol)
were dissolved in 35 mL of anhydrous THF. DEAD (1.89 mL,
12 mmol) was added to the reaction mixture slowly at 0 °C.
The reaction solution was stirred at room temperature for 2.5
5838 J. Org. Chem., Vol. 70, No. 15, 2005