3-Trifluoromethylpyrazolones derived nucleosides: Synthesis and antiviral evaluation

Article abstract of DOI:10.1080/15257770.2019.1591445

Dengue (DENV) viral infection is a global public health problem that infrequently develops life threatening diseases such as dengue hemorrhagic fever (DFS) and dengue shock syndrome (DSS). Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly pathogenic human corona virus with 38% fatality rate of infected patients. A series of 4-arylhydrazono-5-trifluoromethyl-pyrazolones, their ribofuranosyl, and 5′-deoxyribofuranosyl nucleosides were synthesized, geometry optimized using Density functional theory (DFT), and evaluated for their antiviral activity. 2-Nitrophenylhydrazonopyra-zolone derivative 5 showed significant activity against MERS-CoV (EC₅₀ = 4.6 μM). The nucleoside analog 8 showed moderate activity against DENV-2 (EC₅₀ = 10 μM), while the activity was abolished with the corresponding 5′-deoxyribonucleoside analogs. The identified hits in this study set this category of compounds for further future optimizations.

Full text of DOI:10.1080/15257770.2019.1591445

Nucleosides, Nucleotides and Nucleic Acids
ISSN: 1525-7770 (Print) 1532-2335 (Online) Journal homepage: https://www.tandfonline.com/loi/lncn20
3-Trifluoromethylpyrazolones derived nucleosides:
Synthesis and antiviral evaluation
Ayman M. S. Ahmed, Reham A. I. Abou-Elkhair, Alaa M. El-Torky & Abdalla E.
A. Hassan
To cite this article: Ayman M. S. Ahmed, Reham A. I. Abou-Elkhair, Alaa M. El-Torky & Abdalla
E. A. Hassan (2019): 3-Trifluoromethylpyrazolones derived nucleosides: Synthesis and antiviral
evaluation, Nucleosides, Nucleotides and Nucleic Acids, DOI: 10.1080/15257770.2019.1591445
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NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
https://doi.org/10.1080/15257770.2019.1591445
3-Trifluoromethylpyrazolones derived nucleosides:
Synthesis and antiviral evaluation
Ayman M. S. Ahmeda,b, Reham A. I. Abou-Elkhaira,b, Alaa M. El-Torkya, and
Abdalla E. A. Hassana,b
b
aApplied Nucleic Acids Research Center, Zagazig University, Zagazig, Egypt; Chemistry
Department Faculty of Science, Zagazig University, Zagazig, Egypt
ABSTRACT
ARTICLE HISTORY
Received 3 January 2019
Accepted 4 March 2019
Dengue (DENV) viral infection is a global public health prob-
lem that infrequently develops life threatening diseases such
as dengue hemorrhagic fever (DFS) and dengue shock syn-
drome (DSS). Middle East respiratory syndrome coronavirus
(MERS-CoV) is a highly pathogenic human corona virus with
38% fatality rate of infected patients. A series of 4-arylhydra-
zono-5-trifluoromethyl-pyrazolones, their ribofuranosyl, and 50-
deoxyribofuranosyl nucleosides were synthesized, geometry
optimized using Density functional theory (DFT), and eval-
uated for their antiviral activity. 2-Nitrophenylhydrazonopyra-
KEYWORDS
Hydrazonopyrazolones;
nucleosides; antiviral
activity; dengue virus 2;
MERS-CoV
zolone derivative
5 showed significant activity against
MERS-CoV (EC50 ¼ 4.6 lM). The nucleoside analog 8 showed
moderate activity against DENV-2 (EC50 ¼ 10 lM), while the
activity was abolished with the corresponding 50-deoxyribonu-
cleoside analogs. The identified hits in this study set this
category of compounds for further future optimizations.
Introduction
Dengue virus (DENV) is a mosquito-borne virus that causes Dengue fever
(DF) and infrequently develops life threatening diseases such as dengue
hemorrhagic fever (DFS) and dengue shock syndrome (DSS).[1] It is esti-
mated that half of the world’s population is at risk of DENV infection with
390 million people infected annually, including 20,000 deaths.[2] There is
no approved antiviral drug available for treatment of DENV infections.[3]
Middle East respiratory syndrome coronavirus (MERS-CoV) is a highly
pathogenic human coronavirus causes severe acute pneumonia and renal
failure. MERS-CoV has recently emerged in Saudi Arabia[4] and outbreaks
in South Korea.[5] MERS-CoV quickly spread around the globe with a case
fatality rate of 38% according to the World Health Organization (WHO).[6]
Currently, there are no therapies to treat DENV or MERS-CoV infections.
CONTACT Abdalla E. A. Hassan
habdallaa@aol.com
Applied Nucleic Acids Research Center, Zagazig University,
Zagazig, Egypt.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lncn.
ß 2019 Taylor & Francis Group, LLC

2
A. M. S. AHMED ET AL.
The development of novel antiviral compounds that combat is urgently
needed. We have screened a library of small molecules against several RNA
viruses and have identified some 4-arylhydazonopyrazolones derivatives
with antiviral activity against DENV-2 and MERS-CoV. The nucleus of
these compounds have a 3-trifluoromethylpyrazolone, a five membered het-
erocycle ring with two nitrogen atoms at the 1 and 2 positions with a keto
group at the C-5 position thereby mimic the imidazolyl ring of purine
nucleobases. 4-Hydrazonopyrazolones have an interesting structural feature,
that the 4-arylhydrazino group most likely forms an internal hydrogen
bond with the pyrazolone carbonyl forming a pseudo bicyclic 6,5-ring sys-
tem,[7] mimicking the shape-structure of 1-substituted purine. N1-3-fluoro-
phenylinosine (3) and N1-3-fluorophenylhypoxanthine have been reported
to show interesting anti-Hantaan virus activity.[8] Ribavirin (1) and
Bredinine (2) are examples of nucleosides with altered nucleobase struc-
tures, where the first has shown a wide range of activity against DNA and
RNA viruses.[9] Bredinine, an imidazolyl ribonucleoside antibiotic[10] have
reported to have immunosuppressant,[11] anti-rheumatism,[12] and antitu-
mor[13] activities. It is of interest to check whether nucleosides derived
from 3-triflumethyloropyrazolone and its 4-hydrazonopyrazolones deriva-
tives, mimics of/or pseudo 1-arylpurines, would show desirable antiviral
properties. Herein, we wish to report on the synthesis, the Density function
theory (DFT) geometrical optimizations, and the antiviral evaluation of 3-
trifluoromethylpyrazolin-5-one and 4-arylhydrazono-3-methylpyrazolin-5-
ones derived nucleosides 8–15 (Figure 1).
Figure 1. Structures of biologically active nucleobase modified nucleosides 1–3 and 3-trifluor-
methyl-pyrazolones 4–7 and their derived nucleosides 8–15.

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
3
Results and discussion
3-(Trifluromethyl)-pyrazol-1H-5-ol (16) was synthesized from ethyl triflur-
oacetoacetate and hydrazine hydrate in absolute ethanol under reflux tem-
perature.[14] 3-Trifluoromethyl-pyrazolone derivative 16 may exist in three
tautomeric forms (I-III) (Figure 2). The distribution ratio of the three tau-
tomers was calculated using Density functional theory (DFT), at B3LYP/
ꢀ
631G level of theory in gas, nonpolar, and polar phases. In gas phase,
tautomer (I) showed the lowest global and relative energy and the highest
Boltzmann Weight (BW, 0.988), implying its prevalence over the rest of the
tautomers. In nonpolar solvent, the equilibrium of the tautomers yet still in
favor of the tautomer (I) (BW, 0.907), while the population of tautomer
(II) raised to (BW, 0.85). On the other hand, in polar solvent, the equilib-
rium become in favor of tautomer (II) (BW, 0.878) on the expense of
1
tautomer (I) (BW; 0.11). H-NMR of 16 showed an olefinic singlet peak
(5.65 ppm, H-4) and two exchangeable protons at 11.18 and 12.8 ppm. Its
13C-NMR showed three quaternary signals at 154.59, 140.49, and 121.64
corresponding to C5, C3, and the exocyclic CF3, respectively and the latter
group’s 19F-signal appeared at ꢁ61.34 ppm. IR spectrum of 16 showed the
presence of signals characteristic to OH and NH (3270.25, and
3191.14 cmꢁ1) and the presence of two signals characteristic to C¼N group
(1597 and 1499 cmꢁ1). HMBC spectrum of 16 showed a correlation
between the hydroxyl proton and the C-5 carbon supporting the structure
of the tautomer (I) (Figure 2). Treatment of 16 with diazonium salts gener-
ated from o-nitro, m-nitro, m-trifluoromethyl, and p-methyl-aniline in the
presence of NaOAc in absolute EtOH gave the corresponding 4-hydrozono-
pyrazolone derivative 4, 5–7,[15] respectively in good yields (Scheme 2).
Aryl hydrazonopyrazolone derivatives 4, 6, 7 may exist in five tautomeric
forms, while the o-nitrophenyl derivative 5 may exist in eight tautomeric
forms. DFT geometry optipmizations[16] of the tautomeric forms of 4-aryll-
ꢀ
hydrazono-pyrazolo-5-ones was performed at B3LYP/631G level of theory
in gas, nonpolar and polar phases (Figure 3). In contrast to 3-(trifluro-
methyl)-pyrazol-1H-5-ol (16), DFT energy minimization of the 4-arylhy-
drazono derivatives 4–7 showed a predominance of the 2-keto-4-hydrazono
Figure 2. Minimized energy of tautomeric forms of compound 16 using DFT at B3LYP/
ꢀ
631G level.

4
A. M. S. AHMED ET AL.
Figure 3. Geometry optimization of tautomeric forms of compound 4 using DFT at B3LYP/
ꢀ
631G level.
aReagents and conditions. (a)ArN2+Cl-, NaOAc, EtOH, 3 h, 0-5°C; b) i) conc. H2SO4, dry MeOH, 0 °C-r.t., 5 h. ii)
BzCl, dry Pyr., 12h , r.t iii) conc. H2SO4, Ac2O, AcOH, °C-r.t., 5 h. c) BSA, DCM 0 °C, 30 min, rt, then SnCl4 ,
3h; b) NaOCH3, dry MeOH, 3 h., rt.
Scheme 1. Synthesis of ribonucleosides derived 4-aryl-hydrazono-3-trifluoromethylpyrazolone.
aReagents and conditions. a) Ref 17: i) conc. H2SO4, MeOH, acetone, , 0 °C-5 °C, r.t., 5 h; ii) MsCl, Et3N,
DCM, 2h, r.t.; iii) NaBH4, , LiCl, diglyme, 4 h,80 °C; b) BSA, DCM 0 °C, 30 min, rt, then SnCl4 , 3h; c)
NaOCH3, dry MeOH, 3 h., rt.
Scheme 2. Synthesis of 50-deoxyribonucleosides derived 4-aryl-hydrazono-3-trifluoromethylpyrazolone.

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
5
tautomer (I) in gas phase, nonpolar solvent and in polar solvent (Figure 3).
The tautomer (I) population is energetically favored irrespective to the sub-
stituent at the aryl group (H, m-CF3, m-NO2, o-NO2, p-CH3), with lowest
global and relative energy, and the highest BW. The existence of the hydra-
zonopyrazolones 4–7 as a single isomers was confirmed by NMR (1H, 19F,
and 13C) spectra. IR spectra support the structure of the tautomer I, for
example, IR (ATR) spectrum of 4 showed three characteristic signals at
1681, 1557 and 1531 cmꢁ1 corresponding to exocyclic m C¼O, exocyclic m
C¼N, and ring m C¼N groups, respectively. Its 13C-NMR-APT spectrum
showed three quaternary signals of the pyrazolone ring at 158.4 136.5 (q),
and 148.58 ppm corresponding to C3, C5, and C4 respectively.
Glycosylation of the silylated 4-(arylhydrazono)-3-(trifluoromethyl)-4,5-
dihydro-pyrazolones (4–7) with 1-O-acetyl-2,3,5-tri-O-benzoyl-b-D-ribofur-
anose (17)[17] in the presence of SnCl4 in dry CH2Cl2, under Vorbru€ggen
glycosylation conditions provided the corresponding N2-b nucleosides
(18–21), respectively in good yields (Scheme 1). The downfield chemical
shift of the anomeric protons (6.24–6.28 ppm), as a result of the anisotropic
effect of the 2-oxo moiety of the hydrazopyrazolone ring, confirms the gly-
cosylation at the N2-position in 18–21. Deprotection of the hydroxyl
groups of 19–22 was performed under conventional conditions (NaOMe/
MeOH) gave the free nucleosides 8–11, respectively in good yields. The
structures of the free nucleosides 8–11 was assigned by HMBC spectra.
DFT geometry optimization of 8, as an example of the free nucleosides
ꢀ
8–11, was performed at B3LYP/631G level of theory in polar solvent and
reveals that the nucleoside 8 may exist in three tautomeric forms (Figure
4). The 4-hydrazono-2-keto (tautomer I) scored the lowest global and rela-
tive energy with a Boltzmann number of one. All of the three tautomers
showed a preference of the 20-endo conformation of the sugar moiety. 13C-
NMR (APT) spectrum of 8 showed three quaternary carbons of the pyrazo-
lone ring at d 154.55 (C3), 139.99 (q, C-5), 121.61 (q, CF3) and its UV-vis
(MeOH) kmax 230, 390 nm supporting the structure of the tautomer (I) and
in agreement with DFT results. Whether the compounds 6–9 act as a
nucleoside analog or nonnucleoside analogs in their mechanism of interfer-
ing with the viral replication machinery, their 50-deoxy nucleosides 12–15
were synthesized. 1,2,3-Tri-O-acetyl-50-deoxy-b-D-ribofuranose (22) was
synthesized according to literature procedure.[18] Coupling of 4–7 with 22
0
€
under Vorbruggen glycosylation conditions provided the 5 -deoxyribonu-
cleoside derivative 23–26, respectively in good yields (Scheme 2).
Deprotection of 23–26 was performed with NaOMe in MeOH to give the
free nucleosides 12–15 in good yields (Scheme 2). The structures of the
1
nucleosides 23–26 and their free derivatives 12–15 were assigned by H,
13C, 19F-NMR, HMBC, UV-vis, and IR spectroscopy.

6
A. M. S. AHMED ET AL.
Figure 4. Geometry optimization of tautomers(I-III) of compound 6.
Table 1. Antiviral evaluation of compounds 4–11, and 14, 15.
MERS-CoV
Flu A (H1N1)
RSV
HCV
DENV-2
HBV
Compound EC50/(CC50) lM EC50/(CC50) lM EC50/(CC50) lM EC50/(CC50) lM EC50/(CC50) lM EC50/(CC50) lM
4
5
6
8
9
10
11
14
3.2/(6.8)
4.6/>(100)
3.2/(6.8)
56/(68)
32/(>100)
32/(42)
0.71/(0.71)
1.6/(1.6)
0.32/(0.86)
33/(98)
32/68
3.1/(3.6)
ND
3.2/(3.2)
3/(3.3)
3.2/(3.2)
>100/(>100)
>100/(>100)
32/100
ND
6.34/(10.29)
>10.83/(>20)
7.58/(7.78)
20/(>20)
20/(>20)
20/(>20)
20/(>20)
ND
2.4/(8.6)
1.5/(>24)
0.32/(1.5)
10/(>100)
24/(>32)
ND
>87/(87)
100/>(100)
100/>(100)
7.06/(37.34)
8.4/(>38.36)
7.06/37.34
>100/(>100)
>100/(>100)
>100/(>100)
ND
ND
100/>(100)
100/>(100)
0.19/(>100)
ND
ND
ND
ND
ND
ND
15
ND
M128533
Ribavirin
3TC
7.6/(>320)
10/(>320)
0.01/(>2)
PSI-7977
6-azauridine
0.07/(>5)
0.32/(>100)
EC50, compound concentration that reduces viral replication by 50%; CC50, compound concentration that reduces
cell viability by 50%; ND, not determined.
Biology
The antiviral activity of compounds 4–7, 8–11and 14 were assessed against
MERS-COV, DENV-2, Influenza Virus A (Flu A, H1N1), Respiratory syn-
cytial virus (RSV), Hepatitis C virus (HCV), Hepatitis B virus (HBV)
(Table 1). The 4-arylhydrazonopyrazolone derivatives 4–7 showed signifi-
cant activity against the tested viruses, however with varying cytotoxicity.
Of these compounds, the 4-(o-nitrophenylhydrazono)-pyrazolone (5)
showed significant activity against MERS-CoV (EC50 ¼ 4.6 lM, CC50
¼
>100 lM) and against DENV-2 (EC50 ¼ 1.5 lM, CC50 ¼ >24 lM). While
4-(m-trifluoromethylphenylhydrazono)-pyrazolone (6) showed cytotoxicity
to MERS-CoV, Flu A H1N1, RSV, HCV, and DENV-2 cell lines, it showed
moderate activity against HBV (EC50 ¼ 7.06 lM, CC50 ¼ 37.34 lM) with a
narrow selectivity index (SI). A similar pattern of cytotoxicity against all
cell lines was observed with the 4-(m-nitrophenylhydrazono)pyrazolone (4).
Interestingly, the SI of ribonucleoside derivative 8 was improved against
DENV-2 (SI; 10) compared with compound 4 (SI; 3.5). On the other hand,
both the anti-DENV-2 and cytotoxicity was diminished with 4-(o-nitrophe-
nylhydrazono)-pyrazolone ribonucleoside derivative 9. Whether the anti-
viral activity associated with compound 8 is related to its activation to its
ribonucleoside phosphate derivatives, the 50-deoxyribonucleosides 14–15

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
7
was evaluated for their antiviral evaluation. Both the antiviral activity and
the cytotoxicity of these 50-deoxyribonucleosides were abolished. The hits
identified in this study set this category of compounds for further future
optimizations, including the synthesis of the 50-momophosphate prodrugs,
as potential antiviral agents.
Conclusions
We have synthesized a series of 4-(arylhydrazono)-3-trifluoromethyl-1H-
pyrazol-5(4H) -one, bearing electron donating/electron withdrawing sub-
stituents on the aryl moiety, their N2-ribofuranosyl nucleosides and 50-
deoxyribonucleosides, and evaluated their antiviral activity against four
RNA viruses and against HBV. The 4-arylhydrazonopyrazolone derivatives
4 and 5 showed moderate activity against HBV and the later compound
showed significant activity against MERS-CoV. The nucleoside analog 8
showed moderate activity against DENV-2. The identified hits in this study
set this category of compounds for further optimizations as potential anti-
viral agent.
Acknowledgments
The authors wish to thank Dr. Mindy Davis, Dr. Amy Crafts, and Ms. Leatrice Vogel of
the National Institute of Allergy and Infectious Diseases NIAID, NIH for antiviral screen-
ing. Zagazig University utilized the non-clinical and pre-clinical services program offered
by the National Institute of Allergy and Infectious Diseases. The authors wish to thank Dr.
Donald Smee of Utah State University for antiviral screening against DENV-2, MERS-CoV,
Flu A, and RSV. Dr. Michael Murray of Southern Research Institute for antiviral screening
against HBV and HCV. Ms. Shiamaa Khamis, Ms. Hend Maaroof, Mrs. Sarah Housny,
Mrs. Nessrin Khalil of the Applied Nucleic Acids Research Center, Zagazig University for
spectroscopic measurements. This work is partially supported by STDF Grants No. 2698/
4603/5904.
Funding
Science and Technology Fund.
Experimental results and protocols
Material, instruments and general considerations. Starting materials and reagents were pur-
chased from Acros-Organics, Alpha Aesar, and Sigma-Aldrich. Reaction progress was
monitored by TLC analysis using aluminum-backed plates pre-coated with Merck silica gel
60-F254. Column chromatography was carried out on Agela Technologies Flash silica
40–60 mesh. Melting points recorded on Electrothermal IA 9100 apparatus and were
uncorrected. IR spectra (ATR) were recorded on Bruker alpha spectrometer. UV-vis spectra
were recorded on Agilent Cary 60. 1H and 13C-NMR spectra were recorded on Bruker
400 MHz spectrometer. Elemental analysis were recorded on Vario MICRO Cube elemental

8
A. M. S. AHMED ET AL.
analyzer. Computational details: all the structures of the compounds were built using
Wavefunction Spartan 16 V2.0.7 and subjected to energy minimization to remove their
strain energies.[19] DFT was adopted in calculating the equilibrium geometry of the com-
[20]
ꢀ
pounds using B3LYP functional and 6-31G /basis set as built-in in Spartan 16 software.
3-(Trifluromethyl)-pyrazol-1H-5-ol (16). A solution of hydrazine hydrate (3.33 mL,
68.6 mmol) in absolute EtOH (15 mL) was added dropwise to a solution of ethyl 4,4,4-tri-
fluoro-3-oxobutanoate (10 mL, 68.6 mmol) in absolute EtOH (50 mL) at room temperature.
The reaction mixture was heated for 18 hours at reflux temperature. The reaction mixture
was cooled to room temperature and the solvent was concentrated under reduced pressure.
The solid was filtrated to give 16[14] (9.5 g, 91% yield) as a pale yellow solid. M.P.
128–130 ꢂC; IR (ATR): 3270 (ꢀOH), 3191 (ꢀN-H), 1597 (ꢀC¼N), 1499 cmꢁ1; UV-vis (MeOH)
1
kmax 230 nm; H-NMR (DMSO-d6) d 12.83 (1H, s, OH) 11.18 (1H, s, NH), 5.65 (1H, s, H-
4); 13C-NMR (DMSO-d6) d 154.79 (C3), 140.49 (C5), 121.65 (CF3), 83.87 (C4) the signals
were assigned by APT-13C-NMR and 2D-HBMC spectrum; 19F-NMR (DMSO-d6)
d ꢁ61.34.
General procedure (A) for the synthesis of compounds 4–7
To a cold solution of 5-trifluoromethyl-2,4-dihydropyrazol-3-one (1) (3.04 g, 20 mmol) in
EtOH (40 mL) containing NaOAc (3.28 g, 40 mmol), an aqueous solution of the appropriate
aryldiazonium salt (20 mmol/10 mL H2O) was added dropwise with stirring at 0–5 ꢂC. The
reaction mixture was stirred at room temperature for 3 hrs and the formed precipitate was
collected by filtration, washed several times with cold water, dried, and recrystallized from
EtOH to give 4–7.
(Z)-4-(2-(3-nitrophenyl)hydrazono)-5-(trifluoromethyl)-2,4-dihydro-3H-pyrazol-3-one
(4)15a. Yield (1.27 g, 85%) as a yellow crystals. M.P. 253–255 ꢂC; IR 3155 (ꢀN-H), 1681(ꢀ
C¼O); 1531 (ꢀ C¼N), 1557 cmꢁ1 (ꢀ C¼N); UV-vis (MeOH) k
230, 390 nm; 1H-NMR
max
(DMSO-d6) d 12.68 (1H, s, NH) 7.71–8.47 (4H, m, Ar); 13C-NMR (DMSO-d6) d 158.40,
148.58, 143.07, 136.5 (q, C5), 119.54 (q, CF3), 111.55, 118.29, 122.96, 131.07, 120.31, 124.4.
Anal. Clacd for C10H6F3N5O3 (301.19); C, 39.88; H, 2.01; N, 23.25, found C, 39.65; H, 2.21;
N, 23.05.
(Z)-4-(2-(2-nitrophenyl)hydrazono)-5-(trifluoromethyl)-2,4-dihydro-3H-pyrazol-3-one
(5). Yield (1.76 g, 90%) as a yellow solid. M.P. 195–197 ꢂC; IR (ATR) 3166 (ꢀN-
1
H);1671 cmꢁ1 (ꢀC¼O), 1557 (ꢀC¼N); UV-vis (MeOH) kmax 230, 395 nm; H-NMR (DMSO-
d6) d 12.70 (1H, s, NH),7.71–8.45 (4H, m, Ar); 19F-NMR (DMSO-d6) d (ꢁ63.41); 13C-
NMR (DMSO-d6) d 158.33 (C-5, s, C¼O), 142.80 (C-4), 136.50 (q, C-5), 115.59 (q, CF3),
131.15, 148.61 (CH, s, Ar), 111.54, 120.39, 122.91, 124.52, (4CH, s, Ar); Anal. Clacd for
C10H6F3N5O3 (301.19); C, 39.88; H, 2.01; N, 23.25, found C, 39.58; H, 2.28; N, 23.12.
(Z)-3-(Trifluoromethyl)-4-(2-(3-(trifluoromethyl)phenyl)hydrazono)-1H-pyrazol-
5(4H)-one (6). Yield (2.85 g, 90%) as orange crystals. M.P. 205–207 ꢂC (Lit.15b
206–208 ꢂC); IR (ATR) 3205 (ꢀN-H), 1666 (ꢀC¼O); 1556 (ꢀC¼N), 1532(ꢀC¼N); UV-vis
1
(MeOH) kmax 250, 400 nm; H NMR (DMSO–d6) d 12.68 (1H, s, NH), 7.59–7.98 (4H,
m, Ar); 13C NMR (DMSO–d6) d 158.58, 148.58, 143.07, 129.5 (q, C-CF3), 121.54(q,
CF3), 113.58, 113.62, 122.54, 130.14, 120.11, 124.4 (Ar); 19F-NMR d ꢁ63.58, ꢁ64.41;
Anal. Clacd for C11H6F6N4O (324.19); C, 40.75; H, 1.87; N, 17.28; found C, 40.63; H,
1.96; N, 17.04; O.
(Z)-4-(2-(p-Tolyl)hydrazono)-5-(trifluoromethyl)-2,4-dihydro-3H-pyrazol-3-one (7)15c
.
Yield (2.51 g, 95%) as an orange crystals. M.P. 186–188 ꢂC (Lit15. 187 ꢂC); IR (ATR) 3281
1
(ꢀN-H); 1665 (ꢀC¼O), 1547 (ꢀC¼N); UV-vis (MeOH) k
255, 430 nm; H-NMR (DMSO-
max

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
9
d6) d 12.60 (1H, s, NH) 7.26–7.50 (4H, m, Ar), 2.31 (3H, s, CH3); 13C-NMR (DMSO–d6) d
159.06, 143.15, 136.16 (CF3, q), 118.41 (q, C5), 136.91, 138.60, 115.73, 121.39, 122.39,
130.13; 19F-NMR (DMSO–d6) d ꢁ63.21; 19F-NMR d ꢁ63.21; Anal. Clacd for C11H9F3N4O
(270.22) C, 48.89; H, 3.36; N, 20.73; found: C, 48.73; H, 3.56; N, 20.59.
1-O-Acetyl-2,3,5-tri-O-benzoyl-b-D-ribofuranose (17). D-(þ)ribose (5 g; 33.3 mmol)
and methanol (100 mL) were added to a round flask. Thereafter, conc. H2SO4 (0.5 mL) dis-
solved in methanol (1 mL) was slowly added dropwise to the reaction mixture. The
obtained mixture was stirred at room temperature for 5 hrs. The reaction was quenched
with sodium carbonate (10 g), the reaction mixture was filtered and then concentrated
under reduced pressure, to obtain 7.79 g of crude 1-O-methyl-D-ribofuranose as a yellowish
sirup. The crude 1-O-methyl-D-ribofuranose (5.46 g) was dissolved in dry pyridine (16 mL)
and the solution was cooled to 0 ꢂC and benzoyl chloride (15.56 mL) was added dropwise,
the reaction mixture was stirred for 12 hrs. at room temperature. Pyridine was co-evapo-
rated with toluene under reduced pressure, the residue was diluted with ethyl acetate,
washed with saturated solution of sodium carbonate, and brine. The organic layer was
dried over anhydrous sodium sulfate and evaporated under reduced pressure to give (11 g)
of 2,3,5-tri-O-benzoyl-1-O-methyl-D-ribofuranose as a colorless sirup. To a solution of
7.55 g of the crude 2,3,5-tri-O-benzoyl-1-O-methyl-D-ribofuranose in acetic acid (13.2 mL)
and acetic anhydride (2.25 mL), conc. sulfuric acid (0.85 mL) was added dropwise at 0 ꢂC.
The reaction mixture was stirred for 5 hrs at room temperature, and then reaction was
quenched with saturated solution of sodium carbonate. The aqueous layer was extracted
with ethyl acetate. The organic layer was washed by water, dried over anhydrous sodium
sulfate, filtered, and evaporated under reduced pressure. The product was crystallized froꢁm1
iso-propanol to give 17 (6 g, 75%) as a white crystal. M.P. 128–130 ꢂC, IR; 1720 cm
(ꢀC¼O). 1H-NMR (CDCl3) d 8.90–8.07 (2H, m, Ar), 8.02–7.99 (2H, m, Ar), 7.90–7.88
(2H, m, Ar),7.61–7.51 (3H, m, Ar), 7.45–7.32 (6H, m, Ar), 6.43 (1H, s, H-1), 5.92–5.89
(1H, m, H-2), 5.79–7.78 (1H, m, H-3), 4.81–7.75 (2H, m, H-4, and H-5), 4.54–4.49 (1H, m,
H-5), 2.00 (3H, s, CH3), 13C-NMR (CDCl3) d 169.23 (C¼O), 166.14 (C¼O), 165.52
(C¼O),165.18 (C¼O), 133.83 (Ar),133.72 (Ar), 133.42 (Ar), 130.01 (Ar), 129.92 (Ar),
129.74 (Ar), 128.98 (Ar), 128.82 (Ar), 128.70 (Ar), 128.57 (Ar), 128.56 (Ar), 98.56 (C-1),
80.13 (C-2), 75.15 (C-3),71.53 (C-4), 63.88 (C-5), 21.05 (CH3).
General procedure (B) for the synthesis of compounds 18–21. Bis-N,O-trimethylsilyla-
cetamide (1.63 mL, 6.66 mmol) was added to a mixture of 4–7 (5.6 mmol) and 17
(5.6 mmol) in dry dichloromethane (20 mL) and the mixture was stirred for 30 min. at
room temperature under Argon atmosphere. After complete dissolution, the mixture was
cooled to 0 ꢂC, and SnCl4 (16.8 mmol) was added dropwise. The reaction mixture was left
stirring for 3 hrs, then DMSO (5 mL) was added to the reaction mixture. The formed pre-
cipitate was and filtrated off, and the filtrate was washed with H2O. The organic layer was
dried (anhydrous Na2SO4) and evaporated under reduced pressure. The crude residue was
purified by silica gel column chromatography (eluate: Hexane/dichloromethane, 1/1 to
100% dichloromethane) to give 18–21.
2-[(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl](Z)-4-(2-(3-nitrophenyl)hydrazono)-5-(tri-
fluoromethyl)-2,4-dihydro-3H-pyrazol-3-one (18). Compound 18 was prepared by cou-
pling of 4 with 17 according to general procedure (B). Yield (1.9 g, 76%) as a yellow
semi-solid; UV-vis (MeOH) kmax 230, 390 nm; 1H-NMR (DMSO-d6) d 13.56 (1H, d,
HN), 7.36–8.27 (19H, m, Ar), 6.28 (1H, br d, H-10), 6.15 (1H, br dd, H-20), 6.02 (1H, br
dd, H-30), 4.81 (1H, m, H-40), 4.77 (1H, br dd, H-50b), 4.75 (1H, br dd, H-50a); 19F-NMR
(DMSO-d6) d ꢁ64.45; 13C-NMR (DMSO-d6) d 164.54, 164.66, 165.42, 155.60, 148.51,
143.03, 137.54 (q, C-CF3), 1119.32 (q, CF3), 112.25–133.96, 84.70, 78.68, 72.94, 70.76,

10
A. M. S. AHMED ET AL.
63.22. Anal. Clacd for C36H26F3N5O10 (745.62): C, 57.99; H, 3.51; N, 9.39; Found C,
57.75; H, 3.66; N, 9.19.
2-[(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl)](Z)-4-(2-(2-nitrophenyl)hydrazono)-3-(tri-
fluoro-methyl)-1H-pyrazol-5(4H)-one (19). Compound 18 was prepared by coupling of 5
with 17 according to general procedure (B). Yield (1.75 g, 70%) as a yellow semi-solid;
UV-vis (MeOH) k
230, 395 nm; 1H-NMR (DMSO-d6) d 8.53(1H, s, NH), 7.36–8.12
max
(19H, m, Ar), 6.25 (1H, br d, H-10), 6.11–613 (1H, dd, H-20, J¼3.6, J¼5.2 Hz), 5.98 (1H,
br dd, H-30), 5.97 (1H, br t, H-30), 4.82 (1H, m, H-40), 4.64–4.68 (1H, dd, H-50a, J¼3.2,
J¼12.4 Hz), 4.55–4.60 (1H, dd, H-50b, J¼4.0, J¼12.4 Hz); 19F-NMR (DMSO-d6) d ꢁ64.57;
13C-NMR (DMSO-d6) d 164.54, 164.65, 165.42,155.59, 148.53, 142.96, 137.54 (q, CF3),
133.98, 112.25, 84.70, 78.67, 72.93, 70.75, 63.22; Anal. Clacd for C36H26F3N5O10 (745.62):
C, 57.99; H, 3.51; N, 9.39; Found C, 58.02; H, 3.71; N, 9.19.
2-[(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl](Z)-5-(trifluoromethyl)-4-(2-(2-(trifluoro-
methyl)-phenyl)hydrazono)-2,4-dihydro-3H-pyrazol-3-one (20). Compound 20 was
synthesized by coupling of 6 with 17 according to the general procedure (A) as described
above to give (1.8 g, 72%) as a yellow semi-solid; 1H-NMR (DMSO -d6) d 7.43–8.02
(19H, m, Ar) 6.25 (1H, br d, H-10), 6.12 (1H, br dd, H-20), 5.98 (1H, br dd, H-30) 4.82
(1H, m, H-40), 4.65–4.68 (1H, br dd, H-50a), 4.56–4.59 (1H, dd, H-50b, J¼3.2,
J¼12.4 Hz); 19F-NMR (DMSO -d6) d (ꢁ63.62, ꢁ61.53, 2 CF3); 13C-NMR (DMSO–d6) d
164.56, 164. 67, 165.44, 155.76, 137.52, 133.86 (C3), 130.04 (CF3), 133.46, 114.35, 84.69,
78.67, 72.96, 70.78, 63.24; Anal. Clacd for C37H26F6N4O8 (768.63): C, 57.82; H, 3.41; N,
7.29; Found C, 57.96; H, 3.49; N, 7.21.
2-[(2,3,5-tri-O-benzoyl-b-D-ribofuranosyl](Z)-4-(2-(p-tolyl)hydrazono)-3-(trifluoro-
methyl)-1H-pyrazol-5(4H)-one (21). Compound 21 was synthesized by coupling of 7
with 17 according to the general procedure (B). Yield (1.98 g, 75%) as yellow semi-solid;
1
UV-vis (MeOH) kmax 255, 430 nm; H-NMR (DMSO-d6) d 7.29–8.02 (19H, m, Ar), 6.24
(1H, br d, H-10), 6.12 (1H, br dd, H-20), 5.987 (1H, br dd, H-30), 4.82 (1H, m, H-40),
4.66 (1H, br dd, H-50a), 4.57 (1H, br dd, H-50b), 2.32 (3H, s, CH3), 13C-NMR
(DMSO–d6) d 165.25, 165.36,166.45, 155.76, 138.96, 139.35 (q, C3), 133.44 (q, CF3),
133.44, 105.48, 84.64, 78.62, 72.94,70.78, 63.23; 19F-NMR (DMSO-d6) d ꢁ64.30; Anal.
Clacd for C37H29F3N4O8 (714.65): C, 62.18; H, 4.09; N, 7.84; found C, 62.37; H, 4.23;
N, 7.72.
General procedure (C) for deprotection of the nucleosides 18–21 and 23–26. NaOMe
(1 M solution, 2.5 mL) was added dropwise to a solution of the protected nucleoside
(1.28 mmol) in dry MeOH (20 mL) at 0 ᵒC, under argon atmosphere. The reaction mixture
was stirred at room temperature for 3–4 hrs, then neutralized with AcOH. The volatiles
were removed under reduced pressure and the residue was purified by silica gel column
chromatography (eluate: 1%–10% MeOH/dichloromethane) to give 8–11.
2-[(b-D-ribofuranosyl)](Z)-4-(2-(3-nitrophenyl)hydrazono)-5-(trifluoromethyl)-2,4-
dihydro-3H-pyrazol-3-one (8). Compound 8 was synthesized from 18 according to the
general procedure C. Yellow semi-solid (0.5 g, 90%): UV-vis (MeOH) k
230, 390 nm;
max
1H-NMR (DMSO-d6) d 7.72–8.49 (4H, m, Ar), 5.63 (1H, d, H-10, J¼4.4 Hz), 5.36 (1H, s,
OH), 5.13 (IH, s, OH), 4.76 (1H, s, OH), 4.36 (1H, br dd, H-20), 4.07 (1H, br dd, H-30),
3.83 (1H, m, H-40), 3.52 (1H, dd, H-50a J¼4.4, J¼8 Hz), 3.41 (1H, dd, H-5b0, J¼5.6,
J¼11.6 Hz); 19F-NMR (DMSO-d6) d ꢁ63.30; 13C-NMR (DMSO-d6) d 171.98, 149 (q,
C3), 148.53, 123.41(q, CF3), 112.21, 120.59, 128.54, 130.96, 86.11, 84.76, 71.93,70.45,
62.06; 19F-NMR (DMSO-d6) d ꢁ63.30; Anal. Clacd for C15H14F3N5O7 (433.30): C,
41.58; H, 3.26; N, 16.16; found C, 41.36; H, 3.28; N, 16.08.

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
11
2-[(b-D-ribofuranosyl)](Z)-4-(2-(2-nitrophenyl)hydrazono)-3-(trifluoromethyl)-1H-
pyrazol-5(4H)-one (9). Compound 9 was synthesized from 19 according to the general
procedure B. Yellow semi-solid (0.5 g, 90%). UV-vis (MeOH) kmax 230, 395 nm; 1H-
NMR (DMSO-d6) d 7.713–8.48 (4H, m, Ar), 5.63 (1H, d, H-10, J¼4.4 Hz), 5.36 (1H, s,
OH exchangeable with D2O), 5.13 (1H, s, OH exchangeable with D2O), 4.77 (1H, s, OH
exchangeable with D2O), 4.35–4.37 (1H, br dd, H-20), 4.07 (1H, br dd, H-30), 3.83 (1H,
m, H-40), 3.52 (1H, dd, H-50a, J¼4.8, J¼8.0 Hz), 3.43 (1H, dd, H-50b, J¼5.6, J¼11.6 Hz);
19F-NMR (DMSO-d6) d 63.30; 13C-NMR (MHz DMSO-d6) d 172.03, 148.56, 132.87 (q,
C3), 130.95 (q, CF3), 112.21, 120.59, 128.54, 130.96, 86.16, 84.76, 72.03,70.50, 62.12,
45.1. Anal. Clacd for C15H14F3N5O7 (433.30): C, 41.58; H, 3.26; N, 16.16; found C,
41.36; H, 3.28; N, 16.08.
2-[(b-D-Ribofuranosyl](Z)-5-(trifluoromethyl)-4-(2-(2-(trifluoromethyl)phenyl)hydra-
zine-eylidene)-2,4-dihydro-3H-pyrazol-3-one (10). Compound 10 was synthesized
according to the general procedure (C) as described above to give (0.8 gm 89%) as pale
1
yellow foam: UV-vis (MeOH) kmax 250, 400 nm; H-NMR (DMSO-d6) d 7.61–8.02 (4H,
m, Ar), 5.63 (1H, br d, H-10), 5.38 (IH, s, OH), 5.15 (1H, s, OH), 4.75 (1H, s, OH), 4.37
(1H, br dd, H-20), 4.08 (1H, br dd, H-30), 3.86 (1H, m, H-40), 3.52 (1H, dd, H-50a, J¼4.4,
J¼11.6 Hz), 3.42 (1H, dd, H-50a, J¼5.6, J¼11.6 Hz); 19F (DMSO-d6) d ꢁ63.52, ꢁ61.60;
13C-NMR (DMSO–d6) d 166.97, 156.27 (q, C3), 142.47, 134.04 (q, CF3), 114.16, 118.19,
120.84, 125.13, 128.66, 130.94, 86.11, 84.85,71.99, 70.43, 62.02; Anal. Clacd for
C16H14F6N4O5 (456.30): C, 42.12; H, 3.09; N, 12.28; found C, 41.91; H, 3.24; N, 12.13.
2-[b-D-Ribofuranosyl](Z)-4-(2-(p-tolyl)hydrazono)-3-(trifluoromethyl)-1H-pyrazol-
5(4H)-one (11). Compound 11 was synthesized according to general procedure (C).
Yield (0.9 g, 90%) as yellow semi-solid. UV-vis (MeOH) kmax 255, 430 nm; 1H-NMR
(DMSO-d6) d 7.28–7.55 (4H, m, Ar), 5.61 (1H, d, H-10, J¼5.2 Hz), 5.34 (1H, d, 20 OH,
J¼6 Hz), 5.11 (1H, d, 30 OH, J¼4.8 Hz), 4.74 (1H, br t, 50-OH0), 4.35 (1H, br dd, H-20)
4.048–4.082 (1H, br dd, H-30) 3.83 (1H, m, H-40), 3.37–3.55 (2H, br dd, H-50a, H-50b),
2.32 (3H, s, CH3); 19F-NMR (DMSO-d6) d ꢁ63.21; 13C-NMR (DMSO–d6) d 156.72,
136.96, 121.65, 117.74–130.1, 86.04, 84.77, 71.97, 70.44, 62, 20; Anal. Clacd for
C16H17F3N4O5 (402.33): C, 47.77; H, 4.39; N, 13.93; found C, 47.56; H, 4.26; N, 13.85.
1,2,3-Tri-O-acetyl-50-deoxy-b-D-ribofuranose (22). Compound 22 was prepared from
D-(þ) ribose according reference (17) with minor modification. 1H-NMR (CDCl3) d 6.1
(1H, d, J¼1.2 Hz), 5.32 (1H, dd, H-2, J¼1.2, J¼4.8 Hz), 5.08 (1H, dd, H3, J¼4.8,
J¼11.6 Hz), 4.26 (1H, m, H-4); 13C-NMR (CDCl3) d 170.01, 169.58, 169.43, 98.43, 78.13,
75.10, 74.79, 21.18, 20.63, 19.84, 1.09.
2-[(5-deoxy-2,3,-Di-O-acetyl-b-D-ribofuranosyl](Z)-4-(2-(3-nitrophenyl)hydrazono)-5-
(trifluoromethyl)-2,4-dihydro-3H-pyrazol-3-one (23). Compound 23 was prepared by
coupling of 4 with 22 according to general procedure (B). Yield (1.3 g, 78%) as a yellow
foam: UV-vis (MeOH) kmax 230, 390 nm; 1H-NMR (CDCl3) d 13.55 (1H, s, NH);
7.62–8.28 (4H, m, Ar), 5.94 (1H, d, H-10, J¼4.0 Hz), 5.72 (1H, br dd, H-20), 5.23 (1H, br
dd, H-30), 4.26 (1H, m, H-40), 2.12 (6H, s, Ac), 1.42 (3H, d, 50CH3, J¼6.4 Hz); 19F (CDCl3)
d ꢁ64.57; 13C-NMR (CDCl3) d [169.90, 169.73 (2Ac)], 157.90 (C¼O), 149.45 (C-3), 141.61
(C-4), 137.54 (q, CF3), 111.71–131.07 (Ar), 85.24, 78.36, 74.93, 73.09, 20.65, 20.74, 18.85;
Anal. Clacd for C19H18F3N5O8 (501.38): C, 45.52; H, 3.62; N, 13.97; found C, 45.59; H,
3.72; N, 13.81.
2-[(5-deoxy-2,3,-Di-O-acetyl-b-D-ribofuranosyl](Z)-4-[(2-nitrophenyl)hydrazono)]-3-
(trifluoromethyl)-1H-pyrazol-5(4H)-one (24). Compound 24 was prepared by coupling
of 5 with 22 according to general procedure (B). Yield (1.2 g, 72%). as a yellow foam.
1
UV-vis (MeOH) kmax 230, 295 nm; H-NMR (CDCl3) d 13.61 (1H, s NH) 7.63–8.28 (4H,

12
A. M. S. AHMED ET AL.
m, Ar), 5.94 (1H, br d, H-10), 5.72 (1H, br dd, H-20) , 5.24 (1H, br dd, H-30), 4.27 (1H,
m, H-40), 2.12 (6H, s, 2Ac), 1.42 (3H, d, 50-CH3, J¼6.4 Hz);19F-NMR (CDCl3) d ꢁ64.57;
13C-NMR (CDCl3) d 169.89, 169.72 2Ac, 157.91, 149.46, 141.61, 137.54 (q, CF3),
111.71–131.08 (Ar), 85.25, 78.37, 74.93, 73.09, 20.65, 20.74, 18.86; Anal. Clacd for
C19H18F3N5O8 (501.38): C, 45.52; H, 3.62; N, 13.97; found C, 45.61; H, 3.59; N, 13.86.
2-[(5-deoxy-2,3,-Di-O-acetyl-b-D-ribofuranosyl](Z)-5-(trifluoromethyl)-4-(2-(2-(tri-
fluoro-methyl)phenyl)hydrazono)-2,4-dihydro-3H-pyrazol-3-one (25). Compound 25
was prepared by coupling of 6 with 22 according to general procedure (B). Yield (1.45 g,
92%) as a yellow foam; UV-vis (MeOH) kmax 230, 400 nm; 1H-NMR (DMSO-d6) d
7.63–8.04 (4H, m, Ar), 5.82 (1H, br d, H-10), 5.63 (1H, br dd, H-20), 5.14 (1H, br dd, H-
30), 4.20 (1H, m, H-40), 2.08 (6H, s, 2Ac), 1.30 (3H, d, 50-CH3, J¼6 Hz); 19F-NMR (DMSO-
d6) d ꢁ63.62, ꢁ61.53, 2CF3; 13C-NMR (DMSO-d6) d169.9, 169.71, 157.99, 149.47, 140.93,
137.54 (q, CF3), 113.66–130.73 (Ar), 85.21, 78.33, 74.96, 73.11, 20.75, 20.65, 18.87; Anal.
Clacd for C20H18F6N4O6 (524.38): C, 45.81; H, 3.46; N, 10.68; found C, 45.94; H, 3.36;
N, 10.53
2-[(5-deoxy-2,3,-Di-O-acetyl-b-D-ribofuranosyl](Z)-4-(p-tolylhydrazono)-3-(trifluoro-
meth-yl)-1H-pyrazol-5(4H)-one (26). Compound 26 was prepared by coupling of 7 with
22 according to general procedure (B). Yield (1.26 g, 73%) a yellow foam; (MeOH) kmax
1
230, 430 nm; H-NMR (DMSO-d6) d 13.71 (1H, s, NH), 7.28–7.41 (4H, m, Ar), 5.97 (1H,
d, H-10), 5.77 (1H, br dd, H-20), 5.30 (1H, br dd, H-30), 4.24–4.30 (1H, m, H-40), 2.41 (3H,
s, CH3), 2.13 (6H, s, 2Ac), 1.44 (3H, d, 50-CH3, J¼6 Hz); ꢁ19F-NMR (DMSO-d6) d ꢁ64.41;
13C-NMR (CDCl3) d 158.28, 154.1, 149.11, 142.83, 139.54 (q, CF3), 116.97–138.13 (6C-Ar),
86.77, 79.64, 75.64, 74.90, 22.83, 21.71, 21.29, 18.89; Anal. Clacd for C20H21F3N4O6
(470.41): C, 51.07; H, 4.50; N, 11.91; found C, 51.21; H, 4.35; N, 11.79.
2-[(5-deoxy-b-D-ribofuranosyl](Z)-4-(2-(3-nitrophenyl)hydrazono)-5-(trifluor-
omethyl)-2,4-dihydro-3H-pyrazol-3-one (12). Compound 12 was prepared by
deprotection of compound 23 according to general procedure (C). Yield (0.6 g 73%)
as a yellow foam; UV-vis (MeOH) kmax 230, 390 nm; 1H-NMR (DMSO-d6) d
7.73–8.51 (4H, m, Ar), 5.61 (1H, br d, H-10), 5.36 (1H, s, OH exchangeable with
D2O), 5.11 (1H, s, OH exchangeable with D2O), 4.33 (1H, br dd, H-20), 3.94 (1H,
br dd, H-30), 3.877 (1H, m, H-40), 1.20 (3H, d, 50-CH3, J¼6.4 Hz); 19F (DMSO-d6) d
ꢁ63.42; 13C-NMR (DMSO–d6)
d 148.56, 130.61, 137.05, 120.14 (q, CF3),
112.11–131.06 (6C, Ar), 86.47, 74.94, 72.45, 67.47, 19.08; Anal. Clacd for
C
15H14F3N5O6 (417.30): C, 43.17; H, 3.38; N, 16.78; found C, 43.08; H, 3.59;
N, 16.61.
2-[(5-deoxy-b-D-ribofuranosyl](Z)-4-[(2-nitrophenylhydrazono)]-3-(trifluoromethyl)-
1H-pyrazol-5(4H)-one (13). Compound 13 was prepared by deprotection of compound
24 according to general procedure (C). Yield (0.65 gm, 79%) as a yellow semi-solid; UV-
vis (MeOH) kmax 230, 395 nm; 1H-NMR (DMSO-d6) d 7.730–8.514 (4H, m, Ar). 5.61
(1H, br d, H-10), 5.363 (IH, s, OH), 5.11 (1H, s, OH), 4.94 (1H, br dd, H-20), 3.33 (1H, br
dd, H-30), 3.94 (1H, m, H-40), 1.21 (3H, d, 50-CH3, J¼6 Hz); 19F-NMR (DMSO-d6) d
13
ꢁ63.41; C-NMR (0DMSO–d6) d 149.06, 137 72 (q-C5), 130.43, 125.06, 123.43, 122.94,
121.01 (q, CF3), 112.13, 86.46, 76.97, 74.96, 72.47, 19.10; Anal. Clacd for C15H14F3N5O6
(417.30): C, 43.17; H, 3.38; N, 16.78; found C, 43.16; H, 3.49; N, 16.63.
2-[(5-deoxy-b-D-ribofuranosyl](Z)-5-(trifluoromethyl)-4-(2-(2-(trifluoromethyl)-
phenyl)-hydrazono)-2,4-dihydro-3H-pyrazol-3-one (14). Compound 14 was pre-
pared by deprotection of compound 25 according to general procedure (C). Yield
(0.75 g, 90%) a yellow semi-solid; ꢂC; UV-vis (MeOH) kmax 250, 400 nm; 1H-NMR
(DMSO-d6) d 7.64–8.05 (4H, m, Ar), 5.61 (1H, br d, H-10), 5.40 (1H, s, OH

NUCLEOSIDES, NUCLEOTIDES AND NUCLEIC ACIDS
13
exchangeable with D2O), 5.142 (1H, s, OH exchangeable with D2O), 4.34 (1H, br dd,
H-20), 3.94 (1H, br dd, H-30), 3.871 (1H, m, H-40), 1.21 (3H, d, 50-CH3, J¼6 Hz);19F-
NMR d ꢁ63.50, 61.51; 13C-NMR (DMSO–d6) d 156.01, 130.61, 137.05, 125.08 (q,
CF3), 120.72 (q, CF3), 114.05–131.96 (6C, Ar), 86.45, 79.20, 74.88, 72.39, 19.05; Anal.
Clacd for C16H14F6N4O4 (440.30): C, 43.65; H, 3.21; N, 12.72; found C, 43.69; H,
3.16; N, 12.59.
2-[(5-deoxy-b-D-ribofuranosyl](Z)-4-(p-tolylhydrazono)-3-(trifluoromethyl)-1H-pyra-
zol-5(4H)-one (15). Compound 15 was prepared by deprotection of compound 26 accord-
ing to general procedure (C). Yield (0.75 g, 90%) as a yellow semi-solid; UV-vis (MeOH)
kmax 230 nm, 430 nm; 1H-NMR (DMSO-d6) d 7.26–7.54 (4H, m, Ar), 5.37 (1H, s, OH),
5.12 (IH, s, OH), 4.34 (1H, br dd, H-20), 3.93 (1H, br dd, H-30), 3.87 (1H, m, H-40), 2.31
(3H, s, CH3), 1.20 (3H, d, 50-CH3, J¼6.4 Hz), ꢁ19F-NMR (DMSO-d6) ꢁ63.31; 13C-NMR
(DMSO–d6) d 141.64, 138.61, 137.05, 130.00 (q, C3), 76.93 (q, CF3), 116.77, 117.21, 118.27,
120.96, 122.10, 123.64, 86.44, 74.85, 74.85, 74.85, 74.95, 72.47, 20.60, 19.06; Anal. Clacd for
C16H17F3N4O4 (386.33): C, 49.74; H, 4.44; N, 14.50; found C, 49.64; H, 4.53; N, 14.29.
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