Synthesis of 5-phenylcytosine nucleoside derivatives

Article abstract of DOI:10.1135/cccc19960645

Reaction of silylated 5-phenylcytosine with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribose, catalyzed with tin tetrachloride, and subsequent methanolysis afforded 5-phenylcytidine (2). This compound reacted with thionyl chloride in acetonitrile to give cyclic sulfite 3 which on heating in dimethylformamide was converted into 2,2′-anhydro-1-(β-D-arabinofuranosyl)-5-phenylcytosine (4). Analogous reaction of compound 2 with thionyl chloride at reflux gave 5′-chloro-5′-deoxy-2′,3′-cyclic sulfite 5. Its heating in dimethylformamide afforded 5′-chloro-2,2′-anhydro derivative 6, mild alkaline hydrolysis led to 5′-chloro-5′-deoxy-5-phenylcytidine (7). Alkaline hydrolysis of 5-phenyl-2,2′-anhydrocytidine (4) gave 5-phenylcytosine arabinoside 8, whereas the 2,2′-anhydro derivative 6 afforded 1-(5-chloro-5-deoxy-β-D-arabinofuranosyl)-5-phenylcytosine (11). At higher temperature, the final reaction product was 2,5′-anhydro-5-phenylcytidine(12). 5′-Chloro-5′-deoxynucleosides 7 and 11 reacted with tri-n-butyl-stannane to give 5′-deoxyribofuranosyl and 5′-deoxyarabinofuranosyl derivatives 15 and 16. 5-Phenylcytidine (2) was converted into the N⁴-acetate 17 with acetic anhydride. Further reaction with acetic anhydride and hydrogen bromide in acetic acid afforded a mixture of peracetylated 2′-bromo and 3′-bromo derivatives 18 and 19. Reaction with Zn/Cu couple gave 5′-O-acetyl-5-phenyl-2′,3′-didehydro derivative 20 and 2′,3′,5′-tri-O-acetyl-5-phenylcytidine (21). Compound 20 was deblocked to 1-(2,3-dideoxy-β-D-glycero-pent-2-enofuranosyl)-5-phenylcytosine (22). Catalytic hydrogenation of compound 20 over palladium and subsequent deblocking of the protected 2′,3′-dideoxy derivative 23 gave 1-(2, 3-dideoxy-β-D-glycero-pentofuranosyl)-5-phenylcytosine (24).

Full text of DOI:10.1135/cccc19960645

5-Phenylcytosine Nucleoside Derivatives
645
SYNTHESIS OF 5-PHENYLCYTOSINE NUCLEOSIDE DERIVATIVES
Marcela KRECMEROVA, Hubert HREBABECKY and Antonin HOLY
Institute of Organic Chemistry and Biochemistry,
Academy of Sciences of the Czech Republic, 166 10 Prague 6, Czech Republic
Received October 11, 1995
Accepted November 18, 1995
Reaction of silylated 5-phenylcytosine with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribose, catalyzed with
tin tetrachloride, and subsequent methanolysis afforded 5-phenylcytidine (2). This compound reacted
with thionyl chloride in acetonitrile to give cyclic sulfite 3 which on heating in dimethylformamide
was converted into 2,2′-anhydro-1-(β-D-arabinofuranosyl)-5-phenylcytosine (4). Analogous reaction
of compound 2 with thionyl chloride at reflux gave 5′-chloro-5′-deoxy-2′,3′-cyclic sulfite 5. Its heat-
ing in dimethylformamide afforded 5′-chloro-2,2′-anhydro derivative 6, mild alkaline hydrolysis led
to 5′-chloro-5′-deoxy-5-phenylcytidine (7). Alkaline hydrolysis of 5-phenyl-2,2′-anhydrocytidine (4)
gave 5-phenylcytosine arabinoside 8, whereas the 2,2′-anhydro derivative 6 afforded 1-(5-chloro-5-
deoxy-β-D-arabinofuranosyl)-5-phenylcytosine (11). At higher temperature, the final reaction product
was 2,5′-anhydro-5-phenylcytidine (12). 5′-Chloro-5′-deoxynucleosides 7 and 11 reacted with tri-n-butyl-
stannane to give 5′-deoxyribofuranosyl and 5′-deoxyarabinofuranosyl derivatives 15 and 16. 5-Phenyl-
cytidine (2) was converted into the N4-acetate 17 with acetic anhydride. Further reaction with acetic
anhydride and hydrogen bromide in acetic acid afforded a mixture of peracetylated 2′-bromo and 3′-bromo
derivatives 18 and 19. Reaction with Zn/Cu couple gave 5′-O-acetyl-5-phenyl-2′,3′-didehydro deriva-
tive 20 and 2′,3′,5′-tri-O-acetyl-5-phenylcytidine (21). Compound 20 was deblocked to 1-(2,3-dideoxy-β-
D-glycero-pent-2-enofuranosyl)-5-phenylcytosine (22). Catalytic hydrogenation of compound 20 over
palladium and subsequent deblocking of the protected 2′,3′-dideoxy derivative 23 gave 1-(2, 3-dideoxy-
β-D-glycero-pentofuranosyl)-5-phenylcytosine (24).
Key words: 5-Phenylcytosine; Nucleosides; Pyrimidine; 2′,3′-Dideoxynucleoside.
5-Substituted pyrimidine nucleosides with a natural or modified sugar component represent
an important group of compounds with a wide spectrum of biological activities (for a
review see refs1,2). Particular attention received the antiviral 5-halogeno-2′-deoxy-
uridines and 2′-deoxycytidines and analogous 5-alkyl derivatives (2′′-bromovinyl, ethyl,
trifluoromethyl, methoxymethyl, etc.). Some compounds of this group are also effective
cytostatics (5-fluoro-, 5-alkynyl- and 5-perfluoroalkyl-2′-deoxyuridines, 2-deoxy-2-
fluoroarabinosyl uracils and 2-deoxy-2-fluoroarabinosyl cytosines substituted in posi-
tion 5 with iodine or an alkyl group).
In spite of hundreds of publications of synthetic as well as purely biochemical character,
devoted to 5-halogeno and 5-alkyl substituted derivatives, 5-aryl derivatives received
relatively little attention. Only several nucleosides with phenyl or substituted phenyl
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

646
Krecmerova, Hrebabecky, Holy:
group have been synthesized: ribosides, 2′-deoxyribosides and 2′-deoxy-2′-fluoro-
arabinosides3,4. In the series of 5-phenylcytosine nucleosides only 5-phenylcytidine5,
α- and β-anomer of 2′-deoxy-5-phenylcytidine6–8 and 1-(2-deoxy-2-fluoroarabinosyl)-
5-phenylcytosine9 have been prepared. Also a large number of N1-alkyl derivatives of
5-phenylcytosine have been described as cytidine deaminase inhibitors10–13 and accord-
ing to recent studies, various 5-heteroaryl-2′-deoxycytidines and 5-heteroaryl-2′-deo-
xyuridines appeared to be effective antivirals, particularly against herpesviruses8,14–16
.
Since cytosine nucleosides are very effective and clinically employed cytostatics, we
decided to extend our investigation of 5-aryl- and 5-benzylpyrimidine nucleoside
analogs17–19 to a series of 5-phenylcytosine nucleosides modified in the sugar part of
the molecule and to study their cytostatic activity. In addition, we also focused our
attention on the investigation of their potential inhibitory effects against uridine phos-
phorylase, an enzyme catalyzing the phosphorolysis of uracil nucleosides to uracil and
B
B
B
R
R
RO
O
O
O
HO
OR
OH
OH
OR
OH
R
R
R
Bz
H
Cl
H
1
2
7
OH
Cl
8
15
11
16
H
B
NH
N
O
2
O
N
B =
O
OH
12
Cl
O
NH
N
Cl
NH
N
3
2
N
N
O
R
R
O
O
O
OH
O
S
O
R
R
OH
Cl
4
OH
Cl
3
5
6
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

5-Phenylcytosine Nucleoside Derivatives
647
the sugar-1-phosphate and also cleaves many biologically active nucleoside analogs in
the organism, reducing thus the in vivo activity of these compounds. Nucleoside inhibitors
of uridine phosphorylase comprise analogs with hydrophobic groups, some 2,2′-anhydro-
nucleosides and 2′-deoxyglucopyranosyl nucleosides. An extensive research has been
devoted mainly to acyclic analogs derived from 5-benzyluridine (see ref.20 and references
therein).
Our synthesis of 5-phenylcytidine analogs, described in this paper, started from
5-phenylcytosine which can be easily prepared21 from benzyl cyanide. Reaction of silylated
5-phenylcytosine with 1-O-acetyl-2,3,5-tri-O-benzoyl-D-ribose, catalyzed by tin tetra-
chloride, afforded nucleoside 1 which was debenzoylated with methanolic ammonia to
give free 5-phenylcytidine (2). This on reaction with thionyl chloride in acetonitrile at
room temperature afforded the 2′,3′-cyclic sulfite 3 which was converted into 2,2′-anhydro-
5-phenylcytosine (4) by heating in dimethylformamide. When the reaction of 5-phenyl-
cytidine with thionyl chloride was performed at reflux, the reaction product was the
2′,3′-cyclic sulfite 5, bearing chlorine atom in the position 5′. Compound 5 was con-
verted either into 5′-chloro-2,2′-anhydro derivative 6 by heating in dimethylformamide
or into 5′-chloro-5′-deoxy-5-phenylcytidine (7) by reaction with Dowex 1 (CO23− form).
NHR
N
NBz
N
Bz
O
N
N
O
AcO
Cl
O
O
AcO
OAc
OBz
OBz
R
13
9
Ac
H
10
NBz
Bz
O
N
N
Cl
O
BzO
OBz
14
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648
Krecmerova, Hrebabecky, Holy:
A similar reaction scheme has been described already earlier22,23 for the preparation of
some unsubstituted cytosine derivatives. The anhydro ring in 5-phenyl-2,2′-anhydro-
cytidine (6) was opened by treatment with Dowex 1 in the carbonate form. The result-
ing 5-phenylcytosine arabinoside (8) was acetylated with acetic anhydride in pyridine
to afford a mixture of tetraacetyl 9 and triacetyl 10 derivatives.
1-(5-Chloro-5-deoxy-β-D-arabinofuranosyl)-5-phenylcytosine (11) was prepared
similarly as the arabinosyl derivative 8 by alkaline hydrolysis of the corresponding
2,2′-anhydro derivative. The anhydro ring in 5′-chloro-5-phenyl-2,2′-anhydrocytidine
(6) was opened by treatment with potassium carbonate solution at room temperature;
the reaction with Dowex 1 in the carbonate form was less advantageous because the
formed 5′-chloroarabinosyl derivative 11 was sparingly soluble and its isolation was
difficult. At higher temperature (about 70 °C) the reaction with Dowex gave the well
soluble 2′,5′-anhydro derivative 12 arising by subsequent cyclization of the compound 11.
To prepare 5′-deoxyribofuranosyl and 5′-deoxyarabinofuranosyl derivatives 15 and 16,
we first benzoylated the starting 5′-chloro-5′-deoxynucleosides 7 and 11. However, in
NHAc
N
NHAc
N
N
N
O
O
HO
AcO
O
O
R1
R2
OH
OH
R1
Br
R2
17
18
19
OAc
OAc Br
NH2
N
NH2
N
NH2
N
N
N
N
O
O
O
RO
AcO
RO
O
O
O
OAc
OAc
R
R
21
23
24
Ac
H
20
22
Ac
H
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

5-Phenylcytosine Nucleoside Derivatives
649
both cases the usual benzoylation with benzoyl chloride in pyridine afforded the tetra-
benzoyl derivatives 13 and 14, i.e. compounds in which the base bears two benzoyl
groups (see ref.24) which in the subsequent reaction with tributylstannane undergo total
degradation. For this reason, we performed the reduction with tributylstannane with the
free 5′-chloro derivatives 7 and 11.
As the starting compound for the preparation of 2′,3′-dideoxy and 2′,3′-didehydro
derivatives we used 5-phenylcytidine (2) which was first converted into the N4-acetate
17 by reaction with acetic anhydride in boiling methanol. Treatment of the N4-acetate
with acetic anhydride and hydrogen bromide in acetic acid gave a mixture of peracetyl-
ated 2′- and 3′-bromo derivatives 18 and 19. This mixture was subjected to elimination
reaction with the Zn/Cu couple, leading to 2′,3′-didehydro derivatives25. We obtained
the desired 5′-O-acetyl-5-phenyl-2′-3′-didehydro derivative 20, together with 2′,3′,5′-
tri-O-acetyl-5-phenylcytidine (21). On reaction with ammonia, the protected didehydro
derivative 20 afforded 1-(2,3-dideoxy-β-D-glycero-pent-2-enofuranosyl)-5-phenylcyto-
sine (22). Compound 20 was converted into the protected 2′,3′-dideoxy derivative 23 by
catalytic hydrogenation over palladium. Compound 23 reacted with methanolic ammonia to
give 1-(2,3-dideoxy-β-D-glycero-pentofuranosyl)-5-phenylcytosine (24).
The cytostatic activity of all the new 5-phenylcytosine nucleosides was studied on
cell cultures L1210, HeLa and L929. Neither of the compounds exhibited any signifi-
cant cytostatic effect. Also negative were the uridine phosphorylase inhibition assays
(ref.26).
EXPERIMENTAL
Unless stated otherwise, the solutions were evaporated at 40 °C/2 kPa and the compounds were dried
over phosphorus pentoxide at 13 Pa. Thin-layer chromatography was performed on Silufol UV 254
foils (Kavalier, Czech Republic) in the systems S1, ethyl acetate; S2, ethyl acetate–2-propanol 5 : 1;
S3, toluene–acetone 10 : 1; S4, ethyl acetate–acetone–ethanol–water 18 : 3 : 1 : 1; S5, ethyl acetate–
acetone–ethanol–water 18 : 3 : 2 : 2. Spots were detected by UV light at 254 nm. Preparative column
1
chromatography was carried out on silica gel (30–60 µm, Service Laboratory of the Institute). H NMR
spectra (δ, ppm; J, Hz) were measured on a Varian UNITY 200 spectrometer (200.01 MHz) in hexa-
deuteriodimethyl sulfoxide with tetramethylsilane as internal standard. Mass spectra were obtained
with a ZAB-EQ spectrometer (VG Analytical) using the FAB method (Xe, 8 kV, glycerol as matrix).
5-Phenylcytidine (2)
A mixture of 5-phenylcytosine (15 g, 80.05 mmol), hexamethyldisilazane (120 ml) and a catalytic
amount of ammonium sulfate was heated at 150 °C to homogeneity and then for further 1 h. The
solution was taken down, the residue was codistilled with toluene (2 × 100 ml) and dried in vacuo
for 1 h at 50 °C. The obtained silylated base was added to a solution of 1-O-acetyl-2,3,5-tri-O-ben-
zoyl-D-ribose (40.35 g, 80 mmol) in 1, 2-dichloroethane (400 ml), tin tetrachloride (52 ml, 44.4 mmol)
was added and the reaction mixture was stirred at room temperature for 20 h. The solution was
poured into saturated solution of sodium hydrogen carbonate (2 l) and the formed suspension was
filtered through Celite. The organic layer was separated and the aqueous one extracted with chloro-
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

650
Krecmerova, Hrebabecky, Holy:
form (2 × 1 l). The combined organic extracts were washed with aqueous sodium hydrogen carbonate
(1 l), dried over magnesium sulfate and the solvent was evaporated. The residue (benzoyl derivative 1,
56 g) was stirred with methanolic ammonia (500 ml) at room temperature for 5 days. The solution
was taken down, the residue was partitioned between water (2 l) and ethyl acetate (1.5 l) and the
aqueous layer was concentrated to about 400 ml. Crystallization in a refrigerator afforded the product
which was collected and washed successively with ice-cold water, methanol and ether. Yield 19.7 g
(77%) of compound 2. Its physical constants corresponded to the published5 values.
2,2′-Anhydro-1-(β-D-arabinofuranosyl)-5-phenylcytosine Hydrochloride (4)
Thionyl chloride (0.8 ml, 11 mmol) was added to a suspension of compound 2 (2 g, 6.26 mmol) in
dry acetonitrile. The mixture was stirred to dissolution and then for an additional hour at room tem-
perature. Ether (100 ml) was added, the precipitate was filtered, washed with ether and dried. The
obtained sulfite 3 was dissolved in dimethylformamide (60 ml) and heated for 1 h at 100 °C. The
solvent was evaporated, the residue codistilled with toluene (2 × 50 ml) and ethanol (50 ml) and
crystallized from aqueous ethanol. Yield 1.1 g (52%) of white crystals, m.p. 158–168 °C. 1H NMR
spectrum: 3.40 m, 2 H (H-5′); 4.25 m, 1 H (H-4′); 4.51 m, 1 H (H-3′); 5.13 t, 1 H, J(OH,5′) = 4.7
(5′-OH); 5.45 d, 1 H, J(2′,1′) = 6.0 (H-2′); 6.19 d, 1 H, J(OH,3′) = 4.4 (3′-OH); 6.56 d, 1 H, J(1′,2′) = 6.0
(H-1′); 7.39–7.57 m, 5 H (H arom.); 8.40 s, 1 H (H-6); 8.40–9.50 br, 1 H (NH). According to
elemental analysis, the product contained a variable amount of HCl.
2,2′-Anhydro-1-(5-chloro-5-deoxy-β-D-arabinofuranosyl)-5-phenylcytosine Hydrochloride (6)
A mixture of compound 2 (5 g, 15.7 mmol), acetonitrile (60 ml) and thionyl chloride (2.5 ml) was
refluxed for 1.5 h. After cooling to room temperature, the solution was concentrated to a half and
added dropwise with stirring into ether (500 ml). The suspension was set aside in a refrigerator for 1 h,
the product was collected, washed with ether and dried in vacuo. Yield 6.44 g (94%) of amorphous
derivative 5. A solution of this compound (3.86 g, 8.8 mmol) in dimethylformamide (80 ml) was
heated at 110 °C for 1.5 h. After evaporation of the solvent, the residue was codistilled with xylene
(100 ml) and ethanol, dissolved in methanol, briefly boiled with charcoal, filtered and the solvent
was evaporated. The residue was dissolved in a small amount of ethanol and the solution was added
dropwise under stirring into ether (200 ml). The precipitated product was filtered and dried in vacuo
over potassium hydroxide. Yield 3.1 g (99%) of amorphous product which according to elemental
analysis contained a variable amount of HCl.
5′-Chloro-5′-deoxy-5-phenylcytidine (7)
Dowex 1 (CO23− form, 40 ml) was added to a solution of sulfite 5 (2.58 g, 5.91 mmol) in methanol
(100 ml). After stirring at room temperature for 1.5 h, the mixture containing the precipitated product
was diluted with aqueous ethanol (500 ml), filtered and the ion exchanger on the filter was washed
with hot ethanol. The combined filtrates were taken down and the residue was crystallized from
water to give 1.45 g (73%) of white crystalline compound, m.p. 213.5–215.5 °C. For C15H16ClN3O4
(337.8) calculated: 53.34% C, 4.77% H, 10.50% Cl, 12.44% N; found: 53.07% C, 4.77% H,
10.55% Cl, 12.52% N. 1H NMR spectrum: 3.79 dd, 1 H, J(5′a,4′) = 4.6, J(gem) = 11.3 (H-5′a);
3.88–4.05 m, 3 H (H-3′, H-4′ and H-5′b); 4.18 dd, 1 H, J(2′,3′) = 10.4 (H-2′); 5.26 d, 1 H, J = 5.2
(OH); 5.42 d, 1 H, J = 5.8 (OH); 5.87 d, 1 H, J(1′,2′) = 5.2 (H-1′); 6.43 br, 1 H (NH); 7.29–7.56 m,
6 H (H arom. and NH); 7.61 s, 1 H (H-6).
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5-Phenylcytosine Nucleoside Derivatives
651
1-(β-D-Arabinofuranosyl)-5-phenylcytosine (8)
A solution of anhydro derivative 4 (300 mg, 0.89 mmol) in water (10 ml) was stirred with Dowex 1
(CO23− form; 10 ml) at room temperature for 1 h. The ion exchanger was filtered off, washed with
water and the filtrate was concentrated. The residue was crystallized from ethanol to give hygro-
scopic product (210 mg, 72%), m.p. 203.5–205.5 °C. For C15H17N3O5 . 0.5 H2O (328.3) calculated:
1
54.87% C, 5.53% H, 12.80% N; found: 54.48% C, 5.63% H, 12.41% N. H NMR spectrum: 3.55 m,
2 H (H-5′); 3.73 dd, 1 H (H-4′); 3.91 m, 1 H (H-3′); 4.00 m, 1 H (H-2′); 5.03 t, 1 H, J(OH,5′a) = 5.5,
J(OH,5′b) = 5.2 (5′-OH); 5.43 d, 1 H, J = 4.3 (OH); 5.50 d, 1 H, J = 5.5 (OH); 6.12 d, 1 H, J(1′,2′) = 4.0
(H-1′); 6.32 br, 1 H (NH); 7.26–7.52 m, 6 H (H arom. and NH); 7.59 s, 1 H (H-6).
Acetylation of Derivative 8
Compound 8 (100 mg, 0.30 mmol) was codistilled with dry pyridine (2 ml). The residue was dis-
solved in pyridine (1 ml), acetic anhydride (0.13 ml, 1.4 mmol) was added and the solution was
stirred for 5 h at room temperature. The excess acetic anhydride was decomposed with methanol (1 ml),
the solution was stirred for 15 min and the solvent was evaporated. Chromatography on silica gel (20 ml)
in ethyl acetate afforded first N4-acetyl-1-(2,3,5-tri-O-acetyl-β-D-arabinofuranosyl)-5-phenylcytosine
(9) (60 mg, 41%), RF 0.35, as white foam. For C23H25N3O9 (487.5) calculated: 56.67% C, 5.17% H,
1
8.62% N; found: 56.12% C, 5.27% H, 8.35% N. H NMR spectrum: 1.90 s, 6 H (2 × acetyl); 2.11 s, 6 H
(2 × acetyl); 4.34 m, 3 H (H-5′ and H-4′); 5.24 t, 1 H, J(3′,4′) = 3.1 (H-3′); 5.49 dd, 1 H, J(2′,3′) = 2.8
(H-2′); 6.33 d, 1 H, J(1′,2′) = 4.9 (H-1′); 7.29–7.51 m, 5 H (H arom.); 7.81 s, 1 H (H-6); 9.58 s, 1 H
(NH).
Further elution with ethyl acetate–2-propanol (5 : 1) gave 5-phenyl-1-(2,3,5-tri-O-acetyl-β-D-arabino-
furanosyl)cytosine (10) (45 mg, 34%) as colorless sirup (RF 0.32). 1H NMR spectrum: 1.87 s, 3 H
(acetyl); 1.93 s, 3 H (acetyl); 2.10 s, 3 H (acetyl); 4.19–4.23 m, 1 H (H-4′); 4.23–4.38 m, 2 H (H-5′);
5.18 m, 1 H (H-3′); 5.38 dd, 1 H, J(2′,3′) = 3.0 (H-2′); 6.30 d, 1 H, J(1′,2′) = 4.8 (H-1′); 6.47 br, 1 H
(NH); 7.27–7.53 m, 6 H (H-6 and H arom.); 7.56 br, 1 H (NH).
1-(5-Chloro-5-deoxy-β-D-arabinofuranosyl)-5-phenylcytosine (11)
To a stirred solution of anhydro derivative 6 (850 mg, 2.39 mmol) in water (5 ml) was added 10%
aqueous solution of potassium carbonate (10 ml). The reaction mixture was stirred at room tempera-
ture for 30 min, the deposited product was collected on filter, washed with water to neutral reaction
of the filtrate and dried over phosphorus pentoxide. Yield 574 mg (71%) of white crystalline com-
pound, m.p. 237–238 °C. For C15H16ClN3O4 (337.8) calculated: 53.34% C, 4.77% H, 10.50% Cl
1
12.44% N; found: 53.33% C, 4.88% H, 10.54% Cl, 12.45% N. H NMR spectrum: 3.82 m, 2 H (H-5′);
3.94 m, 2 H (H-3′ and H-4′); 4.05 m, 1 H (H-2′); 5.68 d, 1 H, J = 3.8 (OH); 5.74 d, 1 H, J = 4.8
(OH); 6.18 d, 1 H, J(1′,2′) = 3.6 (H-1′); 6.40 br, 1 H (NH); 7.25–7.53 m, 7 H (H arom., NH and H-6).
2′,5′-Anhydro-1-(β-D-arabinofuranosyl)-5-phenylcytosine (12)
Dowex 1 (CO23− form, 35 ml) was added to solution of anhydro derivative 6 (1 g, 2.8 mmol) in water
(60 ml) and the mixture was stirred for 6 h at 70 °C. The reaction was followed by monitoring the
disappearence of the 5′-chloro derivative 11 (TLC in S5; RF: 11, 0.47; 12, 0.38). The reaction mix-
ture was cooled and, together with the Dowex, set aside in a refrigerator overnight. The ion ex-
changer was filtered off and washed with hot ethanol and hot water. The filtrate was evaporated and
the residue was crystallized from methanol–ethanol (1 : 1). The obtained crystalline product was
dried in vacuo for 4 h at 70 °C. Yield 410 mg (45%), m.p. 261–263.5 °C. The product contained
(NMR) crystal ethanol. For C15H15N3O4 . 0.66 C2H5OH (332.0) calculated: 59.09% C, 5.57% H,
Collect. Czech. Chem. Commun. (Vol. 61) (1996)

652
Krecmerova, Hrebabecky, Holy:
12.66% N; found: 58.40% C, 5.70% H, 12.67% N. 1H NMR spectrum: 3.82 brd and 3.93 brd, 2 H,
J(gem) = 9.0 (H-5′); 4.24 dd, 1 H, J = 0.8 and 2.4 (H-4′); 4.44 m, 2 H (H-2′ and H-3′); 5.97 d, 1 H,
J(1′,2′) = 3.4 (H-1′); 6.11 s, 1 H (OH); 6.37 br, 1 H (NH); 7.27–7.52 m, 6 H (H arom. and NH); 7.63 s,
1 H (H-6).
N3,N4-Dibenzoyl-1-(2,3-di-O-benzoyl-5-chloro-5-deoxy-β-D-ribofuranosyl)-5-phenylcytosine (13)
Benzoyl chloride (1.4 ml, 12 mmol) was added at 0 °C to a solution of compound 7 (1 g, 2.96 mmol)
in pyridine (40 ml). The mixture was stirred at 0 °C for 1 h and at room temperature for 24 h. The
excess benzoyl chloride was decomposed with water (50 ml), the solution was stirred for 10 min and
then the solvent was evaporated. The residue was partitioned between chloroform (200 ml) and 1% HCl
(100 ml), the organic layer was washed with saturated solution of sodium hydrogen carbonate (3 × 100 ml)
and dried over magnesium sulfate. Evaporation of the solvent and chromatography on silica gel (560 ml)
in system S3 (RF 0.29) afforded 1.65 g (74%) of compound 13 as white foam. For C43H32ClN3O8
(754.2) calculated: 68.48% C, 4.27% H, 4.70% Cl, 5.57% N; found: 67.94% C, 4.52% H, 5.27% Cl,
1
5.53% N. H NMR spectrum: 4.04 dd, 1 H, J(5′a,4′) = 6.4 (H-5′a); 4.16 dd, 1 H, J(5′b, 4′) = 4.4, J(gem) =
11.7 (H-5′b); 4.37 m, 1 H (H-4′); 5.84 dd, 1 H, J(3′,4′) = 5.9, J(3′,2′) = 6.4 (H-3′); 6.05 dd, 1 H (H-2′);
6.33 d, 1 H, J(1′,2′) = 3.9 (H-1′); 7.05–7.70 m, 21 H (H arom.); 7.83–7.95 m, 4 H (H arom.); 8.50 s, 1 H
(H-6).
N3,N4-Dibenzoyl-1-(2,3-di-O-benzoyl-5-chloro-5-deoxy-β-D-arabinofuranosyl)-5-phenylcytosine (14)
The title compound was prepared from arabinosyl derivative 11 (1.5 g, 4.44 mmol) analogously as
described for compound 13. Yield 2 g (60%) of white foam. TLC (S3, RF 0.23). For C43H32ClN3O8
(754.2): calculated: 68.48% C, 4.27% H, 4.70% Cl, 5.57% N; found: 68.68% C, 4.55% H, 4.87% Cl,
1
5.63% N. H NMR spectrum: 4.17 m, 2 H (H-5′); 4.67 m, 1 H (H-4′); 5.69 dd, 1 H, J(3′,4′) = 5.8 (H-3′);
5.97 dd, J(2′,3′) = 3.1 (H-2′); 6.62 d, 1 H, J(1′, 2′) = 5.2 (H-1′); 7.12–7.39 m, 10 H, 7.45–7.64 m,
10 H, 7.67–7.86 m, 3 H and 8.01–8.12 m, 2 H (H arom.); 8.39 s, 1 H (H-6).
5′-Deoxy-5-phenylcytidine (15)
To a stirred solution of 5′-chloro derivative 7 (700 mg, 2.07 mmol) in dioxane–dimethyl sulfoxide (1 : 1,
30 ml) was added at 130 °C 1 M solution of tributylstannane in toluene (8 ml), followed by
azobis(isobutyronitrile) (350 mg). The solution was stirred for 1 h at 130 °C, cooled and the solvent
was evaporated at 60 °C. The residue was codistilled with dimethylformamide (4 × 30 ml) and
xylene (20 ml) and then chromatographed on silica gel (150 ml) in system S4 (RF: 13, 0.28; 7, 0.36).
Yield 353 mg (56%), m.p. 223–224 °C (ethanol). For C15H17N3O4 (303.3) calculated: 59.40% C,
5.65% H, 13.85% N; found: 58.99% C, 5.54% H, 13.77% N. 1H NMR spectrum: 1.24 d, 3 H, J(5′,4′) = 6.4
(H-5′); 3.67 m, 1 H, J(3′,4′) = 6.1 (H-3′); 3.84 m, 1 H (H-4′); 4.10 m, 1 H, J(2′,3′) = 5.5 (H-2′); 4.97 d,
1 H, J(OH,3′) = 5.8 (3′-OH); 5.28 d, 1 H, J(OH,2′) = 5.2 (2′-OH); 5.74 d, 1 H, J(1′,2′) = 4.0 (H-1′);
6.38 br, 1 H (NH); 7.24–7.64 m, 7 H (H arom., NH and H-6).
1-(5-Deoxy-β-D-arabinofuranosyl)-5-phenylcytosine (16)
Compound 16 was prepared from compound 11 (574 mg, 1.7 mmol) analogously as described for
compound 15. Yield 295 mg (57%) of white crystalline compound, m.p. 242–244.5 °C (ethanol).
TLC: RF 0.24 (S4). For C15H17N3O4 (303.3) calculated: 59.40% C, 5.65% H, 13.85% N; found:
1
58.85% C, 5.61% H, 13.69% N. H NMR spectrum: 1.26 d, 3 H, J(5′,4′) = 6.6 (H-5′); 3.68 m, 1 H,
J(3′,4′) = 2.9 (H-3′); 3.82 m, 1 H (H-4′); 3.97 m, 1 H, J(2′,3′) = 2.1 (H-2′); 5.41 d, 1 H, J(OH,3′) = 4.0
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(3′-OH); 5.49 d, 1 H, J(OH,2′) = 4.9 (2′-OH); 6.08 d, 1 H, J(1′,2′) = 3.8 (H-1′); 6.35 br, 1 H (NH);
7.25–7.54 m, 7 H (H arom., H-6 and NH).
N4-Acetyl-5-phenylcytidine (17)
Acetic anhydride (3 ml) was added to a solution of compound 2 (700 mg, 2.19 mmol) in methanol
(40 ml) and the reaction mixture was rapidly heated to the boil. After about 2 min of boiling, the
mixture was allowed to cool down slowly. After evaporation of the solvent, the residue was codis-
tilled with toluene (2 × 30 ml) and ethanol (30 ml). Crystallization from ethanol afforded 500 mg
(63%) of the product, m.p. 151–153 °C. Further portion (160 mg, 20%) was obtained from the
mother liquors after evaporation and chromatography on silica gel in system S5 (RF 0.47). For
C17H19N3O6 (361.4) calculated: 56.51% C, 5.30% H, 11.63% N; found: 56.30% C, 5.23% H, 11.34% N.
1H NMR spectrum: 2.08 s, 3 H (acetyl); 3.51–3.65 m, 1 H (H-5′a); 3.67–3.81 m, 1 H (H-5′b); 3.93 m,
1 H (H-4′); 4.03 m, 2 H (H-2′ and H-3′); 5.04 d, 1 H, J = 5.5 (OH); 5.22 t, 1 H, J(OH,5′) = 4.6 (5′-OH);
5.57 d, 1 H, J = 4.6 (OH); 5.82 d, 1 H, J(1′,2′) = 2.4 (H-1′); 7.26–7.45 m, 5 H (H arom.); 8.56 s, 1 H
(H-6); 9.66 s, 1 H (NH).
1-(5-O-Acetyl-2,3-dideoxy-β-D-glycero-pent-2-eno)-5-phenylcytosine (20)
and 2′,3′,5′-tri-O-acetyl-5-phenylcytidine (21)
A mixture of N-acetyl derivative 17 (2.48 g, 6.86 mmol), acetic anhydride (2 ml) and 30% hydrogen
bromide in acetic acid (20 ml) was heated under argon for 7 h at 50 °C and then allowed to stand
overnight at room temperature. The mixture was diluted with dichloromethane (80 ml), washed with
Sörensen phosphate buffer, pH 7, (100 ml portions) until the aqueous layer was neutral and then
three times more. The organic extract was dried over magnesium sulfate and the solvent was evap-
orated to give a foam (2.75 g) of bromoacetyl derivatives 18 and 19.
A mixture of acetic acid (23 ml) and copper(II) acetate monohydrate (0.32 g) was heated at 110 °C,
zinc dust (1.89) was added and the mixture was heated at 110 °C for 1 min. The solid was filtered
and washed successively with acetic acid, methanol and dimethylformamide. The thus-prepared
Zn/Cu couple was transferred into the reaction flask and mixed with a solution of the above-de-
scribed mixture of bromoacetyl derivatives 18 and 19 in dimethylformamide (15 ml). The reaction
mixture was stirred at room temperature for 1 h, the solid was filtered off (Celite) and the filtrate
was evaporated. The residue was dissolved in dichloromethane (100 ml) and the solution was washed
with 5% solution of sodium ethylenediaminetetraacetate (Komplexon III, 100 ml). The aqueous phase
was extracted with dichloromethane (2 × 50 ml), the combined extracts were dried over magnesium
sulfate and the solvent was evaporated. Chromatography of the residue on silica gel (500 ml) in sys-
tem S5 afforded compound 21 (RF 0.58; 500 mg, 16%), m.p. 206.5–207.5 °C (2-propanol). For
C21H23N3O8 (445.4) calculated: 56.63% C, 5.20% H, 9.43% N; found: 56.28% C, 5.17% H, 9.19% N.
1H NMR spectrum: 1.90 s, 3 H (acetyl); 2.07 s, 6 H (2 × acetyl); 4.10–4.41 m, 3 H (H- 5′and H-4′);
5.38 m, 1 H (H-3′); 5.53 dd, 1 H, J(2′,3′) = 6.4 (H-2′); 5.91 d, 1 H, J(1′,2′) = 4.3 (H-1′); 6.54 br s,
1 H (NH); 7.27–7.53 m, 5 H (H arom.); 7.64 s, 2 H (NH and H-6).
Further elution gave didehydro derivative 20 (RF 0.43; 700 mg, 31%) as a white foam which was
1
crystallized from 2-propanol, m.p. 150.5–151.5 °C. H NMR spectrum: 1.41 s, 3 H (acetyl); 4.08 dd,
1 H, J(5′a,4′) = 2.4 (H-5′a); 4.23 dd, 1 H, J(5′b,4′) = 3.4, J(gem) = 12.5 (H-5′b); 4.99 m, 1 H (H-4′);
6.06 dt, 1 H (H-3′); 6.33 dt, 1 H, J(2′,3′) = 6.1 (H-2′); 6.44 br, 1 H (NH); 6.95 m, 1 H, J(1′,2′) = 1.7,
J(1′,3′) = 1.5, J(1′,4′) = 3.2 (H-1′); 7.22–7.49 m, 6H (H arom. and H-6); 7.53 br, 1 H (NH).
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654
Krecmerova, Hrebabecky, Holy:
1-(2,3-Dideoxy-β-D-glycero-pent-2-enofuranosyl)-5-phenylcytosine (22)
A solution of acetyl derivative 20 (640 mg, 1.96 mmol) in ethanol–25% aqueous ammonia (1 : 1, 30 ml)
was stirred at room temperature for 3.5 h and then the solvent was evaporated. The residue was codistilled
with ethanol and crystallized from ethanol. Yield 300 mg (54%) of compound 22, not melting up to
300 °C. For C15H15N3O3 (285.3) calculated: 63.15% C, 5.30% H, 14.73% N; found: 62.97% C,
1
5.25% H, 14.42% N. H NMR spectrum: 3.57 dd, 2 H, J(5′,4′) = 3.1, J(5′,OH) = 5.2 (H-5′); 4.79 m,
1 H (H-4′); 4.97 t, 1 H (5′-OH); 5.93 dt, 1 H, J(3′,4′) = 2.1 (H-3′); 6.32 dt, 1 H, J(2′,3′) = 5.8,
J(2′,4′) = 1.5 (H-2′); 6.41 br, 1 H (NH); 6.97 br pent, 1 H, J(1′,2′) = 1.8, J(1′,3′) = 1.5, J(1′,4′) = 3.1
(H-1′); 7.24–7.50 m, 6 H (H arom. and NH); 7.76 s, 1 H (H-6).
1-(5-O-Acetyl-2,3-dideoxy-β-D-glycero-pentofuranosyl)-5-phenylcytosine (23)
Didehydro derivative 20 (1 g, 3.05 mmol) was hydrogenated in methanol (150 ml) over 10% palladium
on carbon (150 mg) at atmospheric pressure and room temperature for 3.5 h. The catalyst was fil-
tered off through Celite, the filter was washed with methanol and the combined filtrates were taken
down. Chromatography of the residue on silica gel (200 ml) in system S5 afforded dideoxy derivative 23
1
(RF 0.44; 320 mg, 32%). H NMR spectrum: 1.67 s, 3 H (acetyl); 1.75 m, 1 H (H-2′a); 1.99 m, 2 H
(H-2′b and H-3′a); 2.33 m, 1 H (H-3′b); 4.20 m, 3 H (H-4′and H-5′); 6.01 dd, 1 H, J(1′,2′a) = 6.7,
J(1′,2′b) = 3.7 (H-1′); 6.33 br, 1 H (NH); 7.28–7.53 m, 6 H (H arom. and NH); 7.58 s, 1 H (H-6).
1-(2,3-Dideoxy-β-D-glycero-pentofuranosyl)-5-phenylcytosine (24)
Acetyl derivative 23 (320 mg, 0.97 mmol) was stirred with methanolic ammonia (100 ml) for 3 h at
room temperature. The solvent was evaporated and the residue was crystallized from ethanol with
addition of a small amount of ether (to slight turbidity). Yield: 190 mg (68%) of compound 24, m.p.
1
197.5–199 °C. Mass spectrum (FAB, glycerol + methanol): 288 (M + H). H NMR spectrum: 1.74–2.04 m,
3 H and 2.18–2.41 m, 1 H (H-2′and H-3′); 3.49 m, 1 H, J(5′a,4′) = 3.5 (H-5′a); 3.69 m, 1 H, J(5′b,4′) = 3.1,
J(gem) = 11.8 (H-5′b); 4.03 m, 1 H (H-4′); 5.03 t, 1 H, J(OH, 5′a) = 5.3, J(OH,5′b) = 5.0 (5′-OH); 5.98 dd,
1 H (H-1′); 6.33 br, 1 H (NH); 7.12–7.52 m, 6 H (H arom. and NH); 8.09 s, 1 H (H-6).
The authors are indebted to the staff of the Analytical Laboratory of this Institute (Dr V. Pechanec,
Head) for the elemental analyses, to Dr J. Kohoutova for the mass spectral measurements and to Dr. I.
Votruba for the cytostatic activity assays. The technical assistance of Dr A. Sterecova is gratefully
acknowledged. This work was supported by a research grant from Rhone-Poulenc Rorer (France).
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