T. Ruman et al. / Bioorganic Chemistry 38 (2010) 87–91
91
Enhancement by Polarization Transfer (DEPT) experiments. All 11
NMR spectra were recorded using pure quartz 5 mm NMR tube.
B
4.4. Synthesis of 50-O-(dihydroxyboronate)-20-30-didehydro-20-30-
dideoxythymidine (3)
Elemental analysis was performed using Elementar Vario EL-3
analyzer. All other reagents and deuterated solvents of the highest
commercially available grade were purchased from Aldrich and
used without further purification. Rubber septa joints were also
purchased from Aldrich. All procedures, including preparation of
samples for the NMR measurements, were carried out under nitro-
gen atmosphere. All the computations were performed with the
Gaussian 03 program [23] on the computer cluster of ICM UW,
Warsaw.
1 (25 mg) was dissolved in anhydrous DMSO (50
l
l) and added
dropwise to the solution of borane–dimethylsulfide complex
(120 l in 2 ml of anhydrous CH2Cl2). The reaction mixture was
stirred for 24 h (0 °C), followed by removal of solvents under vac-
uum. Deoxygenated water (69 l) in THF (2 ml) was added drop-
l
l
wise to the obtained liquid material and the mixture allowed to
react for 2 h, then extracted with water/chloroform (10 + 10 ml)
system. Organic solvents from chloroform phase were vacuum-
evaporated and the resulting solid dried under high vacuum. Com-
pound 3 was obtained with 95% yield and showed 96% purity, as
judged from the 1H NMR spectrum in. Elemental analysis: C
44.75 (calculated 44.81%); H 4.92% (calculated 4.89%); N 10.40%
(calculated 10.45%). 1H NMR (CDCl3, d [ppm]): 8.33 (s, 1H, NH);
7.47 (m, J = 1.3 Hz, 1H, C(6)H); 7.01 (m, J = 1.9 Hz, 1H, C(10)H);
6.32 (m, 1H, C(20)H); 5.84 (m, 1H, C(30)H); 4.91 (m, 1H, C(40)H);
3.93 + 3.80 (m, 2H, C(50)H); 1.86 (d, J = 1 Hz, 3H, Me-C(5)). 13C
NMR (CDCl3, d [ppm]): 163.62 (CC@O); 136.58 (C(6)); 134.50
(C(20); 125.53 (C(30)); 89.92 (C(10)); 87.08 (C(40)); 63.42 (C(50));
12.43 (C(5)-Me). 11B NMR (CDCl3, d [ppm]): 17.76.
4.2. Modified synthetic route for 20-30-didehydro-20-30-dideoxythymi-
dine (stavudine, D4T, 1)
Thymidine (5 g, 20.6 mmol) was added at ꢀ15 °C to solution of
methylsulfonyl chloride (MsCl, 3.52 ml, 45.4 mmol) in pyridine
(43 ml). After 60 min. of vigorous stirring, water (1–2 °C, 600 ml)
was added to the reaction mixture. Resulting mixture was stirred
at 4 °C for another 24 h, and filtered off. White product was then
washed with three 10 ml rations of water (cooled to 0 °C) and dried
under high vacuum.
Reaction product was dissolved in sodium hydroxide solution
(400 ml of 1.06 M solution) and refluxed for 2 h. Acetone
(300 ml) was added to the reaction mixture cooled to 4 °C over a
30 min period. Precipitate that formed was filtered out, washed
twice with acetone (2 ꢂ 20 ml, cooled to 4 °C) and vacuum dried.
The product, in the form of white/grayish crystals, was used in
the following reaction step without further purification. The crys-
tals (0.94 g) were dissolved in anhydrous DMSO (5 ml) and a solu-
tion of potassium tert-butoxide (1.02 g in 2 ml of DMSO) was
added dropwise. After the mixture was allowed to react for 2 h
at room temperature, glacial acetic acid (1:1 v/v in ethanol) was
used to neutralize it to pH ꢃ 7, and the product was extracted with
hexane (2 ꢂ 20 ml). Hexane layer was separated and dried under
high vacuum. The resulting compound 1, obtained with 42% yield,
showed 99.5% purity, as judged from the 1H NMR spectrum. Ele-
mental analysis: C 57.62% (calculated 57.69%) H 5.87% (calculated
5.81%); N 13.42% (calculated 13.45%). 1H NMR (CDCl3, d [ppm]):
7.50 (m, J = 1.3 Hz, 1H, C(6)H); 6.82 (m, J = 1.6 Hz, 1H, C(10)H);
6.35 (m, 1H, C(20)H); 5.86 (m, 1H, C(30)H); 4.87 (m, 1H, C(40)H);
3.67 (m, 2H, C(50)H); 1.74 (d, J = 0.9 Hz, 3H, Me-C(5)).
Acknowledgments
Supported by the Ministry of Education and Science, Poland,
Grant No. N204 088 31/2052 2006–2009. The ICM computer cen-
ter, University of Warsaw, Poland, is acknowledged for the G18-6
computer grant.
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