Synthesis of 2-(3′-Azido- and 3′-Amino-3′-deoxy-β -D-ribofuranosyl)thiazole-4-carboxamide

Article abstract of DOI:10.1081/NCN-120026405

In view of biological activities of tiazofurin and azido or aminosugar nucleosides, novel azido- and amino -substituted tiazofurin derivatives (1 and 2) were efficiently synthesized starting from 1,2; 5,6-di-O-isopropylidene-D-glucose.

Full text of DOI:10.1081/NCN-120026405

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Synthesis of 2-(3′-Azido- and 3′-Amino-3′-deoxy-β-D-
ribofuranosyl)thiazole-4-carboxamide
Cheng Wu Liang a , Myong Jung Kim a , Lak Shin Jeong b & Moon Woo Chun a c
a College of Pharmacy, Seoul National University, Seoul, Korea
b College of Pharmacy, Ewha Womans University, Seoul, Korea
c College of Pharmacy, Seoul National University, Seoul, 151-742, Korea
Published online: 31 Aug 2006.
To cite this article: Cheng Wu Liang , Myong Jung Kim , Lak Shin Jeong & Moon Woo Chun (2003) Synthesis of 2-(3′-Azido- and
3′-Amino-3′-deoxy-β-D-ribofuranosyl)thiazole-4-carboxamide, Nucleosides, Nucleotides and Nucleic Acids, 22:11, 2039-2048,
DOI: 10.1081/NCN-120026405
To link to this article: http://dx.doi.org/10.1081/NCN-120026405
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS
Vol. 22, No. 11, pp. 2039–2048, 2003
Synthesis of 2-(30-Azido- and 30-Amino-30-deoxy-b-D-
ribofuranosyl)thiazole-4-carboxamide
Cheng Wu Liang,1 Myong Jung Kim,1 Lak Shin Jeong,2
and Moon Woo Chun1,
*
1College of Pharmacy, Seoul National University, Seoul, Korea
2College of Pharmacy, Ewha Womans University, Seoul, Korea
ABSTRACT
In view of biological activities of tiazofurin and azido or aminosugar nucleosides,
novel azido- and amino-substituted tiazofurin derivatives (1 and 2) were effi-
ciently synthesized starting from 1,2;5,6-di-O-isopropylidene-D-glucose.
Key Words: IMPDH inhibitor; Amino sugar; Anticancer nucleosides.
INTRODUCTION
Inosine 50-monophosphate dehydrogenase (IMPDH) is a critical enzyme in the
regulation of cell proliferation and differentiation. This enzyme catalyzes the
NADþ-dependent oxidation of inosine 50-monophosphate (IMP) to xanthine 50-
monophosphate (XMP), the rate limiting step in de novo biosynthesis of guanine
nucleotides. Therefore, the biochemical effect of IMPDH inhibition in sensitive cell
types is decrease in intracellular guanine nucleotide levels,[1] and the decrease in
cellular GTP and deoxy GTP pool levels blocks DNA and RNA synthesis in rapidly
*Correspondence: Moon Woo Chun, College of Pharmacy, Seoul National University, Seoul
151-742, Korea; Fax: 82-2-878-9682; E-mail: mjnuh@hanmail.net.
2039
DOI: 10.1081/NCN-120026405
Copyright # 2003 by Marcel Dekker, Inc.
1525-7770 (Print); 1532-2335 (Online)
www.dekker.com

2040
Liang et al.
proliferating tumor cells. Because of its critical role in purine biosynthesis, IMPDH
is a drug design target for anticancer, antiviral, immunosuppressive and antimicro-
bial chemotherapy.[2]
Several compounds have been described as IMPDH inhibitors and among
them, tiazofurin, 2-b-D-ribofuranosylthiazole-4-carboxamide, is a C-nucleoside with
potent inhibitory activity against IMPDH[3] currently undergoing clinical trials as an
antitumor agent.[4] This oncolytic C-nucleoside is converted to the nicotinamide ade-
nine dinucleotide (NAD) analogue, thiazole-4-carboxamide adenine dinucleotide
(TAD), which binds to the NAD cofactor-binding site of the enzyme and inhibits
IMPDH activity.[5] Recently, several analogues of tiazofurin have been synthesized
and are shown in Fig. 1.
It was reported that aminosugar nucleosides possess antiviral and anticancer
activities[6,7] and 30-azido-30-deoxythymidine was converted to 30-amino-30-deoxy-
thymidine in some cells.[8] One of the most important examples is puromycin,[9]
derivative of 30-amino-30-deoxyadenosine.
a
Based upon these findings, it was of interest to put an azido or amino group at
the C-30 position of tiazofurin in order to compare biological activities with the
normal ribonucleoside. An amino group serves as a bioisostere of a hydroxyl group
and 20-hydroxyl substituted 30-aminonucleosides apparently have a higher popu-
lation of N-type nucleoside conformations.[10] Here, we report the synthesis of the
azido- and amino-substituted tiazofurin derivatives (1 and 2), starting from
1,2;5,6-di-O-isopropylidene-D-glucose.
RESULTS AND DISCUSSION
Our synthetic strategy to the target nucleosides is to synthesize ribofuranosyl
cyanide as a key intermediate from 1,2;5,6-di-O-isopropylidene-D-glucose (3) then
to cyclocondense with L-cysteine ethyl ester hydrochloride.
Figure 1. Rationale to the design of the target nucleosides.

Thiazole-4-carboxamide Nucleosides
2041
Starting from commercially available diacetone-D-glucose (3), the hydroxyl
group of 3 was converted to a triflate using trifluoromethanesulfonic anhydride.
Triflate 4 was used in next step without purification and reacted with sodium azide
in DMF to afford the desired azido sugar 5a (44%) and the eliminated enose deriva-
tive 5b (32%), respectively. The ratio of 5a and 5b was dependent on the reagent,
the reaction temperature and the solvent used.[11] The reaction mixture could not
be heated due to an undesired elimination reaction and when the tosylate of 3 was
reacted with sodium azide in presence of 18-crown-6 in DMF, the yield was very
poor. The 5,6-O-isopropylidene of 5a was selectively removed using 75% acetic acid
to give the diol 6. Oxidative cleavage of 6 with sodium periodate followed by reduc-
tion of the resulting aldehyde with sodium borohydride yielded the ribofuranose 7,
which was treated with benzoyl chloride to afford the benzoate 8. It was reported
that the reaction of 1,2,3,5-tetra-O-acetyl-b-D-ribofuranose with cyanotrimethyl-
silane in the presence of BF3 OEt2 gave 3,5-di-O-acetyl-1,2-O-(1-endo-cyanoethyli-
dene)-a-D-ribofuranose.[12] Therefore, to synthesize 1-O-acetyl-2-O-benzoyl derivative,
methylglycoside 9 was prepared from the benzoate 8 by acid-catalyzed methano-
lysis[13] of 8. Benzoylation of 9 afforded the dibenzoate 10, which was treated with
Ac2O=AcOH=H2SO4 to give 1-O-acetyl-3-azido-2,5-di-O-benzoylribofuranose (11).
3-Azido-2,5-di-O-benzoyl-b-D-ribofuranosyl cyanide (12), a key intermediate, was
prepared by reaction of the corresponding acetate 11 with cyanotrimethylsilane and
stannic chloride in dichloromethane[14] (Sch. 1).
Thiazoline 13 was obtained from cyanide 12 by treatment with L-cysteine ethyl
ester hydrochloride in presence of triethylamine according to a previous report[15]
and dehydrogenated by treatment with bromotrichloromethane in combination with
DBU[16] at 0ꢀC to give the thiazole 14. 1H NMR spectrum of 14 showed the presence
of vinyl proton of the thiazole ring. Ester aminolysis and debenzoylation using
methanolic ammonia[17] afforded 30-azido-substituted tiazofurin derivative 1 in high
yield. Catalytic hydrogenation of 1 gave 30-amino-30-deoxytiazofurin (2) (Sch. 2).
The final nucleosides 1 and 2 were assayed against several viruses such as HIV-1,
HSV-1, HSV-2 and HBV. These compounds were found to be inactive against all
viruses tested up to 100 mg=M‘. Compound 1 and 2 have been evaluated in vitro
for their ability to inhibit the growth of Human 143B Osteosarcoma tumor cells,
but found to be completely inactive.
In summary, we have successively synthesized the novel 30-azido- and 30-amino-
30-deoxytiazofurin (1 and 2) by cyclocondensation of glycosyl cyanide and L-cysteine
ethyl ester hydrochloride, followed by dehydrogenation, but the final nucleosides did
not exhibit any significant biological activity.
EXPERIMENTAL
General Methods. NMR spectra were recorded in a 300 MHz apparatus using
tetramethylsilane (TMS) as an internal standard, and the chemical shifts are reported
in ppm (d). Coupling constants are reported in hertz (Hz). Infrared spectra were
recorded in a Perkin-Elmer 1710 FTIR spectrophotometer. Mass spectra recorded
by FAB (Fast atom bombardment) on a VG Tro-2, GC-MS. TLC were carried

2042
Liang et al.
Scheme 1. Reagents and conditions: (a) Tf2O, pyridine, CH2Cl2, 0ꢀC, 1 h; (b) NaN3, DMF,
RT, 16 h, 5a(44%), 5b(32%); (c) 75% AcOH, 55ꢀC, 1.5 h, 90%; (d) 1: NaIO4, EtOH, 0ꢀC, 0.5 h;
2: NaBH4, 0ꢀC, 2 h, 84%; (e) BzCl, pyridine, RT, 3 h, 95%; (f) 1% HCl in MeOH, RT, 2 h, 80%;
(g) BzCl, pyridine, RT, 3 h, 97%; (h) AcOH, Ac2O, c-H2SO4, RT, 30 min, 98%; (i) TMSCN,
SnCl4, CH2Cl2, 70ꢀC, 3 h, 63%.
out on Merck silica gel 60 F254 precoated plates, and silica gel column chromatogra-
phy was performed on silica gel 60, 230 ꢁ 400 mesh, Merck. All anhydrous solvents
were distilled over CaH2 or Na=benzophenone prior to use.
3-Azido-3-deoxy-1,2;5,6-di-O-isopropylidene-a-D-allofuranose (5a) and 3-Deoxy-
1,2;5,6-di-O-isopropylidene-a-D-erythro-hex-3-enofuranose (5b). Trifluoro-methane-
sulfonic anhydride (2.9 mL, 17.24 mmol) was added dropwise to a solution of
1,2;5,6-di-O-isopropylidene-a-D-glucose (3 g, 11.53 mmol) and pyridine (2.8 mL,
34.62 mmol) in dichloromethane (30 mL) at 0ꢀC. The reaction mixture was stirred
for 1 h at 0ꢀC and extracted with dichloromethane and water. The organic layer
was washed with brine, dried (MgSO4), filtered and concentrated to give 4.
The triflate 4 was dissolved in anhydrous DMF (20 mL) and treated with sodium
azide (2.25 g, 34.61 mmol). The reaction mixture was stirred for 16 h at room tem-
perature. Ethyl acetate and water were added and aqueous phase was extracted with

Thiazole-4-carboxamide Nucleosides
2043
Scheme 2. Reagents and conditions: (a) L-cysteine ethyl ester hydrochloride, Et3N, MeOH,
RT, 2 h, 75%; (b) DBU, BrCCl3, CH2Cl2, 0ꢀC, 16 h, 88%; (c) NH3=MeOH, RT, 24 h, 92%;
(d) H2.Pd=C, EtOH, RT, 14 h, 90%.
ethyl acetate (ꢂ3). The combined organic layers were washed with brine, dried
(MgSO4), filtered and evaporated to dryness. The residue was purified by silica gel
flash column chromatography (hexane=EtOAc ¼ 4=1) to give 5a (1.45 g, 5.08 mmol,
44%) as an oil and 5b (0.89 g, 3.67 mmol, 32%) as a solid.
5a: Rf 0.33 (hexane=EtOAc ¼ 4=1); IR (KBr): 2987, 2109, 1377, 1259, 1214,
1
1164, 1065, 1024 cmꢃ1; H NMR (300 MHz, CDCl3): d 5.76 (d, 1H, J ¼ 3.7 Hz, H-
1), 4.70 (t, 1H, J ¼ 4.1 Hz, H-2), 3.95–4.21 (m, 4H, H-4, H-5, H-6), 3.48 (dd, 1H,
J ¼ 4.9, 9.0 Hz, H-3), 1.56, 1.46, 1.36, 1.34 (4 s, 12H, 4 ꢂ CH3); FAB-MS m=z: 286
(M þ H)þ.
5b: Rf 0.52 (hexane=EtOAc ¼ 4=1); IR(KBr): 2988, 2938, 1667, 1376, 1321, 1214,
1
1157, 1073 cmꢃ1; H NMR (300 MHz, CDCl3): d 6.05 (d, 1H, J ¼ 5.1 Hz, H-1), 5.26
(m, 1H, H-3), 5.21 (m, 1H, H-2), 4.54 (dd, 1H, J ¼ 5.9, 6.6 Hz, H-5), 4.10 (dd, 1H,
J ¼ 6.8, 8.3 Hz, H-6a), 3.92 (dd, 1H, J ¼ 5.9, 8.5 Hz, H-6b), 1.44, 1.42, 1.37 (3 s,
12H, 4 ꢂ CH3); FAB-MS m=z: 243 (M þ H)þ.
3-Azido-3-deoxy-1,2-O-isopropylidene-a-D-allofuranose (6). 5a (2.15 g, 7.54 mmol)
was dissolved in 75% acetic acid (30 mL). The reaction mixture was stirred for 2 h at
55ꢀC, evaporated to dryness and coevaporated with toluene. The residue was purified
by silica gel flash column chromatography (hexane=EtOAc ¼ 1=2) to give 6 (1.66 g,
1
6.77 mmol, 90%) as an oil. H NMR (300 MHz, CDCl3): d 5.81 (d, 1H, J ¼ 3.7 Hz,
H-1), 4.75 (dd, 1H, J ¼ 3.7, 4.8 Hz, H-2), 4.07 (dd, 1H, J ¼ 4.2, 9.3 Hz, H-4), 3.75–
4.01 (m, 3H, H-5, H-6), 3.59 (dd, 1H, J ¼ 4.9, 9.4 Hz, H-3), 2.94 (brs, 1H, OH),

2044
Liang et al.
2.51 (brs, 1H, OH), 1.59, 1.38 (2 s, 6H, 2 ꢂ CH3); FAB-MS m=z: 268 (M þ Na)þ,
246 (M þ H)þ.
3-Azido-3-deoxy-1,2-O-isopropylidene-a-D-ribofuranose (7).
A
solution of
sodium periodate (1.57 g, 7.34 mmol) in water (15 mL) was added dropwise to a stir-
red solution of 6 (1.66 g, 6.77 mmol) in EtOH (30 mL) at 0ꢀC. After 30 min, sodium
borohydride (597 mg, 15.8 mmol) was added. The reaction mixture was stirred for 2 h
at 0ꢀC, filtered and evaporated to dryness. The residue was purified by silica gel flash
column chromatography (hexane=EtOAc ¼ 1=1) to give 7 (1.217 g, 5.65 mmol, 84%)
1
as an oil. IR (KBr): 3437, 2988, 2108, 1258, 1110, 1020 cmꢃ1; H NMR (300 MHz,
CDCl3): d 5.79 (d, 1H, J ¼ 3.4 Hz, H-1), 4.72 (t, 1H, J ¼ 4.0 Hz, H-2), 4.09 (m, 1H,
H-4), 3.96 (dd, 1H, J ¼ 2.4, 12.5 Hz, H-5a), 3.66 (dd, 1H, J ¼ 2.9, 12.6 Hz, H-5b),
3.56 (dd, 1H, J ¼ 4.6, 9.5 Hz, H-3), 1.56, 1.35 (2 s, 6H, 2 ꢂ CH3); FAB-MS m=z:
238 (M þ Na)þ, 216 (M þ H)þ.
3-Azido-5-O-benzoyl-3-deoxy-1,2-O-isopropylidene-a-D-ribofuranose (8). To a
stirred solution of 7 (1.217 g, 5.65 mmol) in pyridine (20 mL) was added benzoyl
chloride (0.98 mL, 8.44 mmol) at 0ꢀC. The mixture was stirred for 3 h at room tem-
perature and evaporated to dryness. The residue was dissolved in EtOAc and
extracted with water. The organic layer was washed with saturated NaHCO3 and
brine, dried (MgSO4), filtered and evaporated to dryness. The residue was purified
by silica gel flash column chromatography (hexane=EtOAc ¼ 4=1) to give 8 (1.72 g,
5.39 mmol, 95%) as an oil. IR (KBr): 2108, 1724, 1275, 1213, 1111, 1021,
710 cmꢃ1 1H NMR (300 MHz, CDCl3): d 7.60–8.03 (m, 5H, Ph), 5.85 (d, 1H,
;
J ¼ 3,7 Hz, H-1), 4.78 (dd, 1H, J ¼ 3.7, 4.6 Hz, H-2), 4.66 (dd, 1H, J ¼ 3.1, 12.3 Hz,
H-5a), 4.46 (dd, 1H, J ¼ 4.6, 12.2 Hz, H-5b), 4.37 (m, 1H, H-4), 3.43 (dd, 1H,
J ¼ 4.7, 9.7 Hz, H-3), 1.52, 1.38 (2 s, 6H, 2 ꢂ CH3); FAB-MS m=z: 342 (M þ Na)þ.
3-Azido-5-O-benzoyl-1-O-methyl-3-deoxy-D-ribofuranose (9). To a stirred solu-
tion of 8 (1.72 g, 5.39 mmol) in MeOH (15 mL) was added acetyl chloride (0.2 mL) at
room temperature. After stirring for 3 h at room temperature, the reaction mixture
was neutralized with pyridine and evaporated to dryness. The residue was purified by
silica gel flash column chromatography (hexane=EtOAc ¼ 2=1) to give 9 (1.257 g,
4.3 mmol, 80%) as an oil. IR (KBr): 3462, 2938, 2109, 1722, 1274, 1120, 1070,
713 cmꢃ1 1H NMR (300 MHz, CDCl3): d 7.43–8.10 (m, 5H, Ph), 4.95 (d, 1H,
;
J ¼ 4.4 Hz, a isomer H-1), 4.89 (s, 1H, b isomer H-1), 4.33–4.61 (m, 6H, a and b iso-
mer H-2, H-4, H-5a), 4.13–4.28 (m, 2H, H-5b, b isomer H-3), 3.95 (dd, 1H, J ¼ 4.0,
7.6 Hz, a isomer H-3), 3.45 (s, 3H, a isomer OCH3), 3.33 (s, 3H, b isomer OCH3);
FAB-MS m=z: 294 (M þ H)þ, 262 (M-OCH3)þ.
3-Azido-2,5-di-O-benzoyl-1-O-methyl-3-deoxy-D-ribofuranose (10). To a stirred
solution of 9 (1.257 g, 4.3 mmol) in pyridine (10 mL) was added benzoyl chloride
(0.75 mL, 6.46 mmol) dropwise at room temperature and the reaction mixture was
stirred for 3 h at room temperature. The reaction mixture was evaporated and the
residue was partitioned between ethyl acetate and water. The organic layer was
washed with brine, dried (MgSO4), filtered and evaporated to dryness. The residue
was purified by silica gel flash column chromatography (hexane=EtOAc ¼ 4=1) to

Thiazole-4-carboxamide Nucleosides
2045
give 10 (1.645 g, 4.14 mmol, 97%) as an oil. IR (KBr): 2111, 1725, 1268, 1111, 1070,
1
710 cmꢃ1; H NMR (300 MHz, CDCl3): d 7.45–8.18 (m, 10H, 2 ꢂ Ph), 5.51 (d, 1H,
J ¼ 4.6 Hz, H-2), 5.05 (s, 1H, H-1), 4.63 (m, 1H, H-4), 4.45–4.51 (m, 2H, H-5),
4.32 (dd, 1H, J ¼ 4.6, 7.8 Hz, H-3), 3.38 (s, 3H, OCH3); FAB-MS m=z: 398
(M þ H)þ, 366 (M-OCH3)þ.
1-O-Acetyl-3-azido-2,5-di-O-benzoyl-3-deoxy-D-ribofuranose (11). To a stirred
solution of 10 (1.645 g, 4.14 mmol) in acetic acid (16 mL) were added acetic anhy-
dride (4 mL) and c-H2SO4 (1.12 mL) at room temperature. The reaction mixture
was stirred for 30 min at room temperature and poured into saturated NaHCO3
solution. The mixture was extracted with dichloromethane (ꢂ3). The combined
organic layers were washed with brine, dried (MgSO4), filtered and evaporated to
dryness. The residue was purified by silica gel flash column chromatography
(hexane=EtOAc ¼ 3=1) to give 11 (1.73 g, 4.07 mmol, 98%) as an oil. IR (KBr):
1
2952, 2113, 1726, 1268, 1111, 1022, 7111 cmꢃ1; H NMR (300 MHz, CDCl3): d
7.35–8.02 (m, 10H, 2 ꢂ Ph), 6.52 (d, 1H, J ¼ 4.4 Hz, a isomer H-1), 6.22 (s, 1H, b iso-
mer H-1), 5.52 (d, 1H, J ¼ 4.6 Hz, b isomer H-2), 5.39 (dd, 1H, J ¼ 4.4, 7.5 Hz, a iso-
mer H-2), 4.37–4.78 (m, 6H, a and b isomer H-4, H-5), 4.26 (dd, 1H, J ¼ 4.6, 7.9 Hz,
b isomer H-3), 4.20 (dd, 1H, J ¼ 3.6, 7.5 Hz, a isomer H-3), 2.05 (s, 3H, a isomer
OAc), 1.91 (s, 3H, b isomer OAc); FAB-MS m=z: 448 (M þ Na)þ, 366 (M-OAc)þ.
3-Azido-2,5-di-O-benzoyl-1-cyano-3-deoxy-b-D-ribofuranose (12). To a stirred
solution of 11 (1.73 g, 4.07 mmol) and TMSCN (2.17 mL, 16.27 mmol) in anhydrous
dichloromethane (20 mL) was added 1M solution SnCl4 in dichloromethane (0.8 mL)
dropwise at room temperature. The reaction mixture was refluxed for 3 h and poured
into saturated NaHCO3 solution. The mixture was extracted with dichloromethane
(ꢂ3). The combined organic layers were washed with brine, dried (MgSO4), filtered
and evaporated to dryness. The residue was purified by silica gel flash column chro-
matography (hexane=EtOAc ¼ 3=1) to give 12 (1 g, 2.55 mmol, 63%) as an oil. IR
1
(KBr): 2116, 1725, 1601, 1452, 1267, 1093, 711 cmꢃ1; H NMR (300 MHz, CDCl3):
d 7.46–8.15 (m, 10H, 2 ꢂ Ph), 5.85 (dd, 1H, J ¼ 2.9, 4.6 Hz, H-2), 4.88 (d, 1H,
J ¼ 3.0 Hz, H-1), 4.65 (dd, 1H, J ¼ 3.2, 12.7 Hz, H-5a), 4.54 (dd, 1H, J ¼ 3.4,
12.4 Hz, H-5b), 4.39–4.49 (m, 2H, H-3, H-4); FAB-MS m=z: 415 (M þ Na)þ, 393
(M þ H)þ.
Ethyl 2-(3-Azido-2,5-di-O-benzoyl-3-deoxy-b-D-ribofuranosyl)-thiazoline-4-carb-
oxylate (13). To a stirred solution of 3-azido-2,5-di-O-benzoyl-1-cyano-b-D-ribo-
furanose 12 (763 mg, 1.94 mmol) in dry MeOH (25 mL) was added L-cysteine ethyl
ester hydrochloride (542 mg, 2.92 mmol) followed by TEA (0.4 mL, 2.88 mmol) at
room temperature. The reaction mixture was stirred for 2 h and evaporated to dry-
ness. The residue was dissolved in CH2Cl2 and washed with water, saturated
NaHCO3 solution and brine. The organic layer was dried (MgSO4), filtered and eva-
porated to dryness. The residue was purified by silica gel flash column chromatogra-
phy (hexane=EtOAc ¼ 3=1) to give 13 (758 mg, 1.45 mmol, 75%) as an oil IR (KBr):
1
2984, 2098, 1724, 1272, 1122, 1064, 1025, 713 cmꢃ1; H NMR (300 MHz, CDCl3):
d 7.44–8.13 (m, 10H, 2 ꢂ Ph), 5.84 (m, 1H, H-20), 5.03 (m, 2H, H-10, CHCO2Et),
4.69 (m, 1H, H-40), 4.51 (m, 1H, H-50a), 4.13 (m, 4H, H-30, H-50b, SCH2), 3.37

2046
Liang et al.
(m, 2H, OCH2CH3), 1.24 (m, 3H, OCH2CH3); FAB-MS m=z: 419 (M-OBz)þ; Anal.
calcd for C25H24N4O7S: C, 57.24; H, 4.61; N, 10.68; S, 6.11. Found: C, 57.02; H,
4.51; N, 10.58; S, 6.21.
Ethyl 2-(3-Azido-2,5-di-O-benzoyl-3-deoxy-b-D-ribofuranosyl)-thiazole-4-carboxy-
late (14). To a stirred solution of 13 (758 mg, 1.45 mmol) in anhydrous dichloro-
methane was added 1,8-diazabicyclo[5.4.0]-undec-7-ene (0.43 mL, 2.88 mmol). The
solution was cooled to 0ꢀC and BrCCl3 (0.17 mL, 1.73 mmol) was added dropwise.
The reaction mixture was stirred for 16 h at 0ꢀC and evaporated to dryness. The
residue was dissolved in EtOAc and washed with saturated aqueous NH4Cl (ꢂ3).
The organic layer was dried (MgSO4), filtered and evaporated to dryness. The resi-
due was purified by silica gel flash column chromatography (hexane=EtOAc ¼ 3=1)
to give 14 (666 mg, 1.27 mmol, 88%) as an oil. IR (KBr): 2983, 2113, 1725, 1267,
1
1096, 711 cmꢃ1; H NMR (300 MHz, CDCl3): d 7.42–8.24 (m, 11H, SCH, 2 ꢂ Ph),
5.96 (dd, 1H, J ¼ 2.9, 4.9 Hz, H-20), 5.58 (d, 1H, J ¼ 2.9 Hz, H-10), 4.80 (dd, 1H,
J ¼ 3.0, 12.3 Hz, H-50a), 4.36 (m, 5H, H-30, H-40, H-50b, OCH2CH3), 1.37 (t, 3H,
J ¼ 7.06 Hz, OCH2CH3); FAB-MS m=z: 545 (M þ Na)þ, 523 (M þ H)þ; Anal. calcd
for C25H22N4O7S: C, 57.46; H, 4.24; N, 10.72; S, 6.14. Found: C, 57.66; H, 4.20; N,
10.62; S, 6.24.
2-(3-Azido-2,5-di-O-benzoyl-3-deoxy-b-D-ribofuranosyl)thiazole-4-carboxamide
(1). A mixture of 14 (666 mg, 1.27 mmol) in saturated NH3 in MeOH (20 mL) was
stirred for 24 h at room temperature and evaporated to dryness. The residue was puri-
fied by silica gel flash column chromatography (CH2Cl2=MeOH ¼ 7=1) to give 1
(334 mg, 1.17 mmol, 92%) as a white foam. IR (KBr): 3427, 2925, 2109, 1660,
1
1260, 1047 cmꢃ1; H NMR (300 MHz, CD3OD): d 8.19 (s, 1H, SCH), 5.00 (d, 1H,
J ¼ 5.4 Hz, H-10), 4.45 (t, 1H, J ¼ 5.5 Hz, H-20), 4.02 (d00d00, 1H, J ¼ 3.9, 4.1,
5.4 Hz, H-40), 3.92 (dd, 1H, J ¼ 5.4, 5.6 Hz, H-30), 3.71 (dd, 1H, J ¼ 3.9, 12.2 Hz,
H-50a), 3.64 (dd, 1H, J ¼ 4.4, 12.2 Hz, H-50b); additional signals in 1H NMR
(300 MHz, DMSO-d6): d 7.71 (brs, 1H, NH2), 7.57 (brs, 1H, NH2), 6.15 (d, 1H,
J ¼ 5.6 Hz, OH), 5.01 (t, 1H, J ¼ 5.3 Hz, OH); FAB-MS m=z: 308 (M þ Na)þ, 286
(M þ H)þ; Anal. calcd for C9H11N5O4S: C, 37.89; H, 3.89; N, 24.55; S, 11.24.
Found: C, 37.54; H, 4.08; N, 24.25; S, 11.42.
2-(3-Amino-2,5-di-O-benzoyl-3-deoxy-b-D-ribofuranosyl)thiazole-4-carboxamide
(2). To a solution of 1 (280 mg, 0.98 mmol) in EtOH (20 mL) was added 5% Pd=C
(100 mg) and the reaction mixture was degassed and stirred at one atmosphere of
hydrogen for 14 h at room temperature. The catalyst was removed by filtration
and the filtrate was evaporated to dryness. The residue was recrystalized from
MeOH=EtOAc to give 2 (230 mg, 0.89 mmol, 90%) as a white solid. IR (KBr): 3433,
1
2918, 1658, 1381, 1043 cmꢃ1; H NMR (300 MHz, DMSO-d6): d 8.18 (s, 1H, SCH),
7.64 (br s, 1H, NH2), 7.55 (br s, 1H, NH2), 4.99 (d, 1H, J ¼ 1.95 Hz, H-10), 4.01
(dd, 1H, J ¼ 1.95, 9.72 Hz, H-20), 3.63 (m, 2H, H-40, H-30), 3.55 (m, 1H, H-50a),
2.96 (dd, 1H, J ¼ 4.9, 8.5 Hz, H-50b), 1.41 (brs, 2H, NH2); FAB-MS m=z:
260 [M þ H]þ; Anal. calcd for C9H13N3O4S: C, 41.69; H, 5.05; N, 16.21; S, 12.37.
Found: C, 41.52; H, 5.15; N, 16.01; S, 12.29.

Thiazole-4-carboxamide Nucleosides
2047
REFERENCES
1. (a) Eugui, E.M.; Almquist, S.T.; Mullwe, C.D.; Allison, A.C. Lymphocyte-
selective cytostatic and immunosuppressive effects of mycophenolic acid in
vitro: Role of deoxyguanosine nucleotide depletion. Scand. J. Immunol. 1991,
33, 161; (b) Franklin, T.J.; Morris, W.P. Pharmacodynamics of the inhibition of
GTP synthesis in vivo by mycophenolic acid. Adv. Enzyme Regul. 1994, 34, 107.
2. Franchetti, P.; Cappellacci, L.; Grifantini, M. IMP dehydrogenase as a target
of antitumor and antiviral chemotherapy. Farmaco 1996, 51, 457; and refer-
ences therein.
3. Jayaram, H.N.; Dion, R.L.; Glazer, R.J.; Johns, D.G.; Robins, R.K.;
Srivastava, P.C.; Cooney, D.A. Initial studies on the mechanism of action of
a new oncolytic thiazole nucleoside, 2-b-D-ribofuranosylthiazole-4-carboxa-
mide (NSC 286193). Biochem. Pharmacol. 1982, 31, 2371.
4. (a) Tricot, G.J.; Jayaram, H.N.; Lapis, E.; Natsumeda, Y.; Nichols, C.R.;
Kneebone, P.; Heerema, N.; Weber, G.; Hoffman, R. Biochemically directed
therapy of leukemia with tiazofurin, a selective blocker of inosine 50-phosphate
dehydrogenase activity. Cancer Res. 1989, 49, 3696; (b) Wright, D.G.; Boosalis,
M.S.; Waraska, K.; Osrly, L.J.; Weeintraub, L.R.; Vosburgh, E. Tiazofurin
effects on IMP-dehydrogenase activity and expression in the leukemia cells of
patients with CML blast crisis. Anticancer Res. 1996, 16, 3349.
5. Lui, M.S.; Faderam, M.A.; Liepnieks, J.J.; Natsumeda, Y.; Alah, E.; Jayaram,
H.N.; Weber, G. Modulation of IMP dehydrogenase activity and guanylate
metabolism by tiazofurin (2-b-D-ribofuranosylthiazole-4-carboxamide). J. Biol.
Chem. 1984, 259, 5078.
6. Suhadolnik, R.J. Nucleoside Antibiotics; Wiley-Interscience: New York, 1970.
7. Suhadolnik, R.J. Nucleosides as Biological Probes; Wiley-Interscience: New
York, 1979.
8. Balzarini, J. Metabolism and mechanism of antiretroviral action of purine and
pyrimidine derivatives. Pharm. World Sci. 1994, 16, 113.
9. Baker, B.R.; Joseph, J.P.; Williams, J.H. Synthetic studies. VII. Partial syn-
thesis of amino acid analogs. J. Am. Chem. Soc. 1955, 77, 1.
10. Herdewijn, P.; Balzarin, J.; Masanori, B.; Pauwels, R.; Van Aerschot, A.;
Janssen, G.; De Clercq, E. Synthesis and anti-HIV activity of different sugar-
modified pyrimidine and purine nucleosides. J. Med. Chem. 1988, 31, 2040
and references therein.
11. Neufellner, E.; Kapeller, H.; Griengl, H. A novel access to derivatives of 3-
azido-3-deoxy-4a-carba-a-DL-ribofuranose potential intermediates for the syn-
thesis of carbachryscandin and carbapuromycin. Tetrahedron 1988, 54, 11,043.
12. Utimoto, K.; Wakabayashi, Y.; Horiie, T.; Inoue, M.; Shishiyama, Y.;
Obayashi, M.; Nozaki, H. Cyanotrimethylsilane as a versatile reagent for
introducing cyanide functionality. Tetrahedron 1983, 39, 967.
13. Bolon, P.J.; Sells, T.B.; Nuesca, Z.M.; Purdy, D.F.; Nair, V. Novel isomeric
dideoxynucleosides as potential antiviral agents. Tetrahedron 1994, 50, 7747.
14. Utimoto, K.; Horiie, T. A facile preparation of O-acelated b-D-ribofuranosyl
cyanide, an important intermediate of c-nucleoside synthesis. Tetrahedron Lett.
1982, 23, 237.

2048
Liang et al.
15. Ramasamy, K.S.; Bandaru, R.; Averett, D. A new synthetic methodology for
tiazofurin. J. Org. Chem. 2000, 65, 5849.
16. Williams, D.R.; Lowder, P.D.; Gu, Y.G.; Brooks, D.A. Studies of mild dehy-
drogenations in heterocyclic systems. Tetrahedron Lett. 1997, 38, 331.
17. Srivastava, P.C.; Pickering, M.V.; Allen, L.B.; Streeter, D.G.; Campbell, M.T.;
Witkowski, J.T.; Sidwell, R.W.; Robins, R.K. Synthesis and antiviral activity
of certain thiazole C-nucleosides. J. Med. Chem. 1977, 20, 236.
Received February 21, 2003
Accepted August 11, 2003