Preparation of thymidine-4′-C-carboxylic acid and its derivatives

Article abstract of DOI:10.1135/cccc19971128

3′,5′-Di-O-benzoyl-4′-C-hydroxymethylthymidine (3) was prepared in four steps from 3′-O-(tert-butyldimethylsilyl)-4′-C-hydroxymethylthymidine (1). Oxidation of 3 with pyridinium dichromate afforded 3′,5′-di-O-benzoylthymidine-4′-C-carboxylic acid (4) whic

Full text of DOI:10.1135/cccc19971128

1128
Hrebabecky, Holy:
PREPARATION OF THYMIDINE-4′-C-CARBOXYLIC ACID AND ITS
DERIVATIVES
1
Hubert HREBABECKY and Antonin HOLY
Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic,
166 10 Prague 6, Czech Republic; e-mail: 1 hubert@uochb.cas.cz
Received April 4, 1997
Accepted May 7, 1997
3′,5′-Di-O-benzoyl-4′-C-hydroxymethylthymidine (3) was prepared in four steps from 3′-O-(tert-
butyldimethylsilyl)-4′-C-hydroxymethylthymidine (1). Oxidation of 3 with pyridinium dichromate af-
forded 3′,5′-di-O-benzoylthymidine-4′-C-carboxylic acid (4) which on debenzoylation gave free
thymidine-4′-C-carboxylic acid, (3R,2S,5R)-3-hydroxy-2-hydroxymethyl-5-(5-methyl-2,4-dioxo-
1,2,3,4-tetrahydropyrimidin-1-yl)tetrahydrofuran-2-carboxylic acid, (5). Esterification of acid 5 with
diazomethane afforded the methyl ester 6. Its isopropyl ester 7 was obtained by transesterification of
the methyl ester 6. Reaction of ester 6 with ammonia and hydrazine led to the respective amide 8 and
hydrazide 9. Upon reaction with 1,1′-carbonyldiimidazole, the protected acid 4 was converted into
the corresponding imidazolide 11, which, without isolation, was treated with glycinamide, dimethyl-
amine and aminoethanol to give aminocarbonylmethylamide 12a, N,N-dimethylamide 13a and
hydroxyethylamide 14a, respectively. The free amides 12b, 13b and 14b were obtained by methano-
lysis of corresponding benzoates with methanolic sodium methoxide. Neither of the prepared com-
pounds exhibited significant activity against HIV.
Key words: (3R,2S,5R)-3-Hydroxy-2-hydroxymethyl-5-(5-methyl-2,4-dioxo-1,2,3,4-tetrahydropyrimidin-1-yl)-
tetrahydrofuran-2-carboxylic acid; Thymidine-4′-C-carboxylic acid.
The present study is a part of our program aimed at the synthesis of 2′-deoxy-4′-C-sub-
stituted nucleoside analogues and study of relationship between structure and antiviral
activity1. The biological activity of these derivatives depends crucially on the character
of substitution in the positions 4′-C and 3′, the antiviral activity being associated with
an electron-withdrawing substituent in position 4′-C and a free hydroxy group in posi-
tion 3′ (see refs2–5). Particularly the 4′-C-azido derivative2,3 and the 4′-C-cyano deriva-
tive4 exhibit high anti-HIV activity.
The aim of the present communication was to synthesize thymidine-4′-C-carboxylic
acid ((3R,2S,5R)-3-hydroxy-2-hydroxymethyl-5-(5-methyl-2,4-dioxo-1,2,3,4-tetrahydro-
pyrimidin-1-yl)tetrahydrofuran-2-carboxylic acid, 5) and its derivatives and to study
whether the presence of the electron-withdrawing carboxyl group in the position 4′-C
also affects the antiviral activity.
As the starting compound for the synthesis of thymidine-4′-C-carboxylic acid and its
derivatives (Scheme 1), we made use of the already described4 3′-O-silyl derivative 1.
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

Thymidine-4’-C-carboxylic Acid
1129
Its tritylation with trityl chloride in pyridine at room temperature and subsequent desi-
lylation with tetrabutylammonium fluoride afforded the trityl derivative 2 in 65% over-
all yield. Also in this case we observed the already described1d,4,5 higher reactivity of
the 4′-C-hydroxymethyl group in comparison with the 5′-hydroxy group. The trityl
derivative 2 was benzoylated with benzoyl chloride in pyridine and the obtained diben-
zoyl trityl derivative was detritylated to give the dibenzoyl derivative 3.
B
B
HO
HO
B
B
RO
HO
TrO
BzO
HO
O
O
O
O
a, b
e
c, d
HOOC
OTBDMS
OR
OH
OBz
R
1
2
3
Bz
H
4
5
B
B
HO
HO
XOC
O
O
f
g or h or i
5
CH OOC
3
OH
OH
X
OCH(CH )
6
7
3 2
NH
8
9
2
NHNH
2
B
B
BzO
RO
XOC
O
O
j
k or l or m
4
N
OC
N
OBz
11
OR
X
R
NHCH CONH
Bz
H
12a
12b
13a
2
2
O
N
NHCH CONH
2
2
CH
3
HN
B =
N(CH )
Bz
3 2
O
N(CH )
3 2
H
13b
14a
14b
NHCH CH OH
Bz
H
2
2
NHCH CH OH
2
2
o
a) TrCl, pyridine; b) Bu NF, THF; c) benzoyl chloride, pyridine; d) 80% acetic acid, 60 C; e) pyridinium
4
dichromate, DMF; f) CH N ; g) sodium 2-propoxide, propan-2-ol; h) NH , MeOH; i) hydrazine; j) 1,1’-car-
2
2
3
bonyldiimidazole; k) glycinamide; l) dimethylamine; m) ethanolamine
SCHEME 1
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

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Hrebabecky, Holy:
The hydroxymethyl to carboxyl oxidation can be performed using several proce-
dures. Oxidation with permanganate6a or platinum-catalyzed oxidation with air6b,6c
usually give low yields. Moreover, these methods cannot be used for oxidation of the
hydroxymethyl derivative 3 because they require an aqueous medium in which com-
pound 3 is insoluble. Oxidation with ruthenium tetroxide, generated from ruthe-
nium(III) chloride with periodate, can be used only for purine nucleosides6d. Also a
modified method6e, employing potassium peroxydisulfate in strongly alkaline medium
for generation of the ruthenium tetroxide, could not be used because the (hydroxy-
methyl)thymidine 3 is protected by the alkali-labile benzoyl groups. Finally, oxidation
with pyridinium dichromate6f proved to be the method of choice which afforded the
acid 4 in a high yield. Acid 5 was obtained by debenzoylation of the acid 4 with methanolic
sodium methoxide. Methyl ester 6 was prepared by esterification of acid 5 with diazo-
methane. The ethereal solution of diazomethane was added dropwise to a cool solution
of the acid to avoid methylation of the base and the reaction was monitored by TLC.
Transesterification of the methyl ester 6 with sodium 2-propoxide in propan-2-ol af-
forded the isopropyl ester 7. The ester 6 was converted into amide 8 and hydrazide 9 by
reaction with methanolic ammonia and hydrazine, respectively.
O
CH
3
HN
O
N
BzO
O
C H NHCONOC
6 11
OBz
H
C
6
11
10
For the preparation of other derivatives we tried a method7 used in the peptide chemistry.
This consisted in activation of the carboxyl with 1,3-dicyclohexylcarbodiimide by for-
ming a reactive O-isourea derivative. Although the reaction was carried out at –40 °C,
the yield of the subsequent reaction was low and we isolated mainly the unreactive
N-acylurea derivative 10. We found a better way via imidazolide 11 which was pre-
pared in situ by reaction of the protected acid 4 with 1,1′-carbonyldiimidazole in di-
methylformamide, and without isolation treated with glycinamide, dimethylamine or
ethanolamine. The thus obtained protected derivatives 12a, 13a and 14a were methano-
lyzed with methanolic sodium methoxide to give the free derivatives 12b, 13b and 14b.
The synthesized derivatives were tested for antiviral activity. Neither of them ex-
hibited significant activity in vitro8. Although it is known that electronegative substi-
tuents in position 4′-C increase the antiviral activity, the electronegativity alone
obviously is not sufficient to elicit the activity.
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

Thymidine-4’-C-carboxylic Acid
1131
EXPERIMENTAL
Melting points were determined on a Kofler block and are uncorrected. 1H NMR spectra (δ, ppm; J, Hz)
were measured on a Varian UNITY 200 instrument in hexadeuteriodimethyl sulfoxide with tetra-
methylsilane as internal standard. Column chromatography was performed on silica gel 30–60 µm
(Service Laboratories of this Institute) and thin-layer chromatography (TLC) on Silufol UV 254 foils
(Kavalier, Votice). Solvents were evaporated at 30–60 °C (bath)/2 kPa and compounds were dried at
13 Pa over phosphorus pentoxide.
1-(2-Deoxy-4-C-hydroxymethyl-5-triphenylmethyl-α-L-threo-pentofuranosyl)thymine (2)
Trityl chloride (3.35 g, 12 mmol) was added to a solution of silyl derivative 1 (ref.4) (4.64 g, 12 mmol)
in pyridine (80 ml). The mixture was set aside at room temperature overnight, the solvent evaporated
and the residue partitioned between water (100 ml) and ethyl acetate (300 ml). The organic layer was
separated, washed with water (3 × 100 ml), dried over magnesium sulfate and taken down. The
residue was dissolved in tetrahydrofuran (70 ml) and 1 M solution of tetrabutylammonium fluoride in
tetrahydrofuran was added. The solution was heated at 40 °C for 4 h, concentrated to about one quar-
ter of the original volume, diluted with ethyl acetate, washed with water (3 × 50 ml) and dried over
magnesium sulfate. The solvent was evaporated and the residue chromatographed on a column of
silica gel (250 g) in ethyl acetate to yield 4.01 g (65%) of trityl derivative 2 as a solid foam. For
C30H29N2O6 (513.5) calculated: 70.16% C, 5.69% H, 5.46% N; found: 69.87% C, 5.98% H, 5.19% N.
1H NMR spectrum: 1.80 s, 3 H (CH3); 1.99–2.11 m and 2.18–2.32 m, 2 H (2 × H-2′); 3.01 d, 1 H,
J(5a′,5b′) = 10.1 (H-5a′); 3.26 d, 1 H (H-5b′); 3.55 dd, 1 H, J(a,b) = 11.1, J(CHaH,OH) = 4.9
(CHaH-O); 3.73 dd, 1 H (CHbH-O); 4.31–4.38 m, 1 H (H-3′); 5.07–5.13 m, 2 H (3-OH, CH2OH);
6.22 d, 1 H, J(1′,2a′) = 6.4, J(1′,2b′) = 7.3 (H-1′); 7.20–7.43 m, 15 H (H-arom.); 7.77 d, 1 H, J = 1.2
(H-6); 11.29 s, 1 H (H-3).
1-(3-O-Benzoyl-4-C-benzoyloxymethyl-2-deoxy-α-L-threo-pentofuranosyl)thymine (3)
A solution of benzoyl chloride (1.4 ml) in pyridine (14 ml) was added dropwise during 4 h to a
stirred solution of trityl derivative 2 (2.57 g, 5 mmol) in pyridine (25 ml). Methanol (2 ml) was
added and after 15 min the reaction mixture was concentrated. The residue was partitioned between
ethyl acetate (100 ml) and water (30 ml), the organic phase was washed three times with water, dried
over magnesium sulfate and the solvent was evaporated. The residue was dissolved in 80% aqueous
acetic acid (40 ml) and boiled for 15 min. After cooling, the separated trityl alcohol was removed by
filtration, washed with 80% aqueous acetic acid and the combined filtrates were taken down. Column
chromatography on silica gel (150 g) in ethyl acetate–toluene (2 : 1) gave 1.72 g (72%) of dibenzoyl
derivative 3 as a solid foam. For C25H24N2O8 (480.5) calculated: 62.49% C, 5.04% H, 5.83% N;
found: 62.20% C, 5.16% H, 5.62% N. 1H NMR spectrum: 1.80 s, 1 H (CH3); 1.99–2.11 m, 2 H (2 × H-2′);
3.01 d, 1 H, J(a,b) = 10.1 (CHaH-O); 3.26 d, 1H (CHbH-O); 3.55 dd, 1 H, J(5a′,5b′) = 11.1,
J(5′,OH) = 4.9 (H-5a′); 3.77 dd, 1 H (H-5b′); 4.31–4.38 m, 1 H (H-3′); 5.07–5.13 m, 2 H (3′-OH,
5′-OH); 6.22 dd, 1 H, J(1′,2a′) = 6.4, J(1′,2b′) = 7.3 (H-1′); 7.20–7.43 m, 15 H (H-arom.); 7.77 d, 1 H,
J = 1.2 (H-6); 11.29 s, 1 H (H-3).
3′,5′-Di-O-benzoylthymidine-4′-C-carboxylic Acid (4)
Dibenzoyl derivative 3 (2.40 g, 5 mmol) was dissolved in a solution of pyridinium dichromate (17 g,
45 mmol) in dimethylformamide (18 ml). After standing at room temperature overnight, the solution
was diluted with water (20 ml) and the product was extracted with ethyl acetate (3 × 80 ml). The
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

1132
Hrebabecky, Holy:
combined extracts were washed with 5% hydrochloric acid and water, dried over magnesium sulfate,
and the solvent was evaporated. Yield 2.02 g (82%) of chromatographically pure acid 4 as a solid
foam. For C25H20N2O9 (492.4) calculated: 60.97% C, 4.09% H, 5.69% N; found: 60.59% C, 4.31% H,
5.42% N. 1H NMR spectrum: 1.67 s, 3 H (CH3); 2.55–2.87 m, 2 H (2 × H-2′); 4.79 d, 1 H,
J(5a′,5b′) = 11.8 (H-5a′); 4.85 d, 1 H (H-5b′); 6.00 dd, 1 H, J(3′,2a′) = 4.9, J(3′,2b′) = 7.6 (H-3′);
6.55 t, 1 H, J(1′,2a′) = J(1′,2b′) = 6.9 (H-1′); 7.47–7.73 m and 7.94–7.99 m, 6 H (H-6, H-arom.);
11.41 s, 1 H (H-3); 13.68 bs, 1 H (COOH).
Thymidine-4′-C-carboxylic Acid (5)
A solution of dibenzoate 4 (1.97 g, 4 mmol) in 0.3 M methanolic sodium methoxide (20 ml) was set
aside at room temperature overnight and filtered through a column of Dowex 50 (H+ form, 10 ml).
The column was washed with methanol and the combined filtrates were taken down. Crystallization
from a small amount of methanol afforded 995 mg (87%) of free acid 5, m.p. 218–221 °C. For
C11H14N2O7 (286.2) calculated: 46.15% C, 4.93% C, 9.79% N; found: 45.97% C, 4.91% H, 9.79% N.
1H NMR spectrum: 1.77 s, 3 H (CH3); 2.17 dd, 2 H (2 × H-2′); 3.72 d, 1 H, J(5a′,5b′) = 11.9 (H-5a′);
3.79 d, 1 H (H-5b′); 4.42 t, 1 H, J(3′,2a′) = J(3′,2b′) = 5.5 (H-3′); 6.35 t, 1 H, J(1′,2a′) = J(1′,2b′) = 6.7
(H-1′); 7.70 d, 1 H, J = 1.3 (H-6); 11.30 s, 1 H (H-3).
Methyl Thymidine-4′-C-carboxylate (6)
An ethereal solution of diazomethane (1 mol/l, 3 ml) was added dropwise to a stirred and cooled (ice
bath) solution of acid 5 (859 mg, 3 mmol) in methanol (12 ml). After evaporation of the solvent, the
residue was chromatographed on a column of silica gel (80 g) in ethyl acetate–acetone–ethanol–water
(19 : 3 : 2 : 1) to give 790 mg (88%) of ester 6 as a solid foam. For C12H16N2O7 (300.3) calculated:
1
48.00% C, 5.37% H, 9.33% N; found: 47.71% C, 5.51% H, 9.05% N. H NMR spectrum: 1.78 d, 3 H,
J(CH3,6) = 0.6 (CH3); 2.07–2.29 m, 2 H (2 × H-2′); 3.65 s, 3 H (CH3O); 3.78 bd, 2 H (2 × H-5′);
4.42 m, 1 H, J(3′,2a′) = J(3′,2b′) = 4.5, J(3′,OH) = 5.1 (H-3′); 5.28 t, 1 H, J(5′,OH) = 5.5 (5′-OH);
5.70 d, 1 H (3′-OH); 6.37 t, 1 H, J(1′,2a′) = J(1′,2b′) = 6.7 (H-1′); 7.66 d, 1 H (H-6); 11.31 s, 1 H
(H-3).
Isopropyl Thymidine-4′-C-carboxylate (7)
A suspension of methyl ester 6 (150 mg, 0.5 mmol) in 0.1 M solution of sodium 2-propoxide in propan-2-ol
(5 ml) was stirred at room temperature for 24 h and then neutralized with Dowex 50 (H+ form).
Water was added until the product dissolved. The ion-exchange resin was filtered off and washed
with water, the combined filtrates were concentrated and the residue was chromatographed on a col-
umn of silica gel (15 g) in ethyl acetate–acetone–ethanol–water (40 : 6 : 2 : 1). Crystallization from
propan-2-ol–ether afforded 125 mg (76%) of isopropyl ester 7, m.p. 198–201.5 °C. For C14H20N2O7
(328.3) calculated: 51.21% C, 6.14% H, 8.53% N; found: 50.97% C, 6.30% H, 8.53% N. 1H NMR
spectrum: 1.20 d, 6 H, J(CH3,CH) = 6.0 ((CH3)2C); 1.77 s, 3 H (CH3); 2.08–2.28 m, 2 H (2 × H-2′);
3.68–3.85 m, 2 H (2 × H-5′); 4.39–4.47 m, 1 H (H-3′); 4.91 m, 1 H ((CH3)2CH); 5.23 t, 1 H,
J(OH,5′) = 5.5 (5′-OH); 5.26 d, 1 H, J(OH,3′) = 4.9 (3′-OH); 6.33 t, 1 H, J(1′,2a′) = J(1′,2b′) = 6.7
(H-1′); 7.68 d, 1 H, J = 1.2 (H-6); 11.31 s, 1 H (H-3).
Thymidine-4′-C-carboxamide (8)
A solution of ester 6 (150 mg, 0.5 mmol) in 12% methanolic ammonia (2 ml) was set aside at room
temperature for 6 days. After evaporation, the residue was crystallized from water to give 130 mg
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

Thymidine-4’-C-carboxylic Acid
1133
(91%) of amide 8, m.p. 187–189 °C. For C11H15N3O6 (285.3) calculated: 46.31% C, 5.30% H,
14.73% N; found: 46.03% C, 5.48% H, 14.76% N. 1H NMR spectrum: 1.77 d, 3 H, J = 0.7 (CH3);
2.02–2.17 m, 2 H (2 × H-2′); 3.60–3.84 m, 2 H (2 × H-5′); 4.26–4.32 m, 1 H (H-3′); 5.27 t, 1 H,
J(OH,5′) = 4.3 (5-OH); 5.34 d, 1 H, J(OH,3′) = 4.6 (3′-OH); 6.38 dd, 1 H, J(1′,2a′) = 5.5, J(1′,2b′) =
8.85 (H-1′); 7.17 s and 7.36 s, 2 H (NH2); 7.89 d, 1 H, J = 1.2 (H-6); 11.18 s, 1 H (H-3).
Thymidine-4′-C-carbohydrazide (9)
Hydrazine sulfate (195 mg, 1.5 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-ene (0.3 ml) were added
to a solution of ester 6 (150 mg, 0.5 mmol) in methanol (3 ml). The mixture was stirred at 55 °C for
4 days. The crystalline product was collected on a filter and crystallized from aqueous methanol.
Yield 113 mg (75%) of hydrazide 9, m.p. 221–224 °C. For C11H16N4O6 (300.3) calculated: 44.00% C,
1
5.37% H, 18.66% N; found: 43.76% C, 5.44% H, 18.94% N. H NMR spectrum: 1.77 d, 3 H, J = 0.8
(CH3); 2.01–2.24 m, 2 H (2 × H-2′); 3.63 d, 1 H J(5a′,5b′) = 11.6 (H-5a′); 3.82 d, 1 H (H-5b′);
4.29–4.33 m, 1 H (H-3′); 6.33 dd, 1 H, J(1′,2a′) = 5.5, J(1′,2b′) = 8.8 (H-1′); 7.82 d, 1 H, J = 1.2
(H-6); 9.08 s, 1 H (NH).
N-[(Aminocarbonyl)methyl]-3′,5′-di-O-benzoylthymidine-4′-C-carboxamide (12a)
A. A solution of 1,3-dicyclohexylcarbodiimide (113 mg, 0.55 mmol) in dimethylformamide (0.5 ml)
was added dropwise at –40 °C to a stirred solution of acid 4 (246 mg, 0.5 mmol) in dimethylform-
amide (1.5 ml). The mixture was stirred at –15 °C for 30 min and then a solution of glycinamide
hydrochloride (61 mg, 0.55 mmol) in dimethylformamide (0.5 ml) was added, followed by N,N-diiso-
propylethylamine (0.1 ml, 0.6 mmol). The mixture was allowed to warm to room temperature and set
aside for 24 h. The solvent was evaporated and the residue dissolved in ethyl acetate (30 ml). The
solution was washed with water (3 × 15 ml), dried and taken down and the residue was chromato-
graphed on a column of silica gel (25 g) in ethyl acetate–toluene (2 : 1) to give 245 mg (70%) of the
dicyclohexylurea derivative 10 as a solid foam. For C38H44N4O9 (700.8) calculated: 65.13% C, 6.33% H,
1
8.00% N; found: 65.32% C, 6.50% H, 7.80% N. H NMR spectrum: 0.95–1.83 m, 20 H (10 × CH2
in cyclohexyl); 1.40 s, 3 H (CH3); 2.39–2.65 m, 2 H (2 × H-2′); 3.76–3.87 m, 2 H (2 × CH in cyclo-
hexyl); 4.83 d, 1 H, J(5a′,5b′) = 11.9 (H-5a′); 4.88 d, 1 H (H-5b′); 6.05 d, 1 H, J(3′,2b′) = 4.0 (H-3′);
6.46 dd, 1 H, J(1′,2a′) = 5.4, J(1′,2b′) = 9.5 (H-1′); 7.34 s, 1 H (NH); 7.45–8.14 m, 11 H (H-6,
H-arom.); 11.42 s, 1 H (H-3).
Elution with ethyl acetate–acetone–ethanol–water (40 : 6 : 3 : 1) afforded 60 mg (22%) of glycin-
amide derivative 12a as solid foam. For C27H26N4O9 (550.5) calculated: 58.90% C, 4.76% H, 10.18% N;
found: 58.67% C, 4.91% H, 9.89% N. 1H NMR spectrum: 1.66 s, 3 H (CH3); 2.47–2.83 m, 2 H (2 × H-2′);
3.37–3.88 m, 2 H (NCH2); 4.70 d, 1 H, J(5a′,5b′) = 11.6 (H-5a′); 4.98 d, 1 H (H-5b′); 5.89 d, 1 H,
J(3′,2b′) = 4.3 (H-3′); 6.55 dd, 1 H, J(1′,2a′) = 5.5, J(1′,2b′) = 9.2 (H-1′); 7.12 s, 1 H and 7.33 s, 1 H
(NH2); 7.48–8.03 m, 11 H (H-6, H-arom.); 8.54 t, 1 H, J(NH,CH2) = 5.6 (NH); 11.43 s, 1 H (H-3).
B. 1,1′-Carbonyldiimidazole (90 mg, 0.55 mmol) was added to a solution of acid 4 (246 mg, 0.5 mmol)
in dimethylformamide (2 ml). After standing for 1 h at room temperature, glycinamide hydrochloride
(61 mg, 0.55 mol) and diisopropylethylamine (42 µl, 0.3 mmol) were added. The solution was
allowed to stand for 3 h, the solvent was evaporated and the residue was partitioned between water
(10 ml) and ethyl acetate (20 ml). The organic layer was separated, washed with water, 2% hydro-
chloric acid, water, 5% sodium hydrogen carbonate solution, dried and the solvent was evaporated.
Yield 220 mg (80%) of chromatographically pure derivative 12a as solid foam.
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Hrebabecky, Holy:
N-[(Aminocarbonyl)methyl]thymidine-4′-C-carboxamide (12b)
A solution of benzoyl derivative 12a (220 mg, 0.4 mmol) in 0.1 M methanolic sodium methoxide (3 ml)
was allowed to stand at room temperature overnight. The mixture was neutralized with Dowex 50
(H+ form), the ion-exchange resin was filtered off, washed with methanol and the combined filtrates
were concentrated. The residue was mixed with ether and the amorphous solid was filtered and
washed with ether. Yield 120 mg (88%) of derivative 12b. For C13H18N4O7 (342.3) calculated:
1
45.61% C, 5.30% H, 16.37% N; found: 45.39% C, 5.44% H, 16.09% N. H NMR spectrum: 1.78 s,
3 H (CH3); 2.06–2.28 m, 2 H (2 × H-2′); 3.31–3.88 m, 4 H (NCH2, 2 × H-5′); 4.32–4.37 m, 1 H
(H-3′); 5.36 t, 1 H, J(OH,5′) = 5.5 (5′-OH); 5.86 d, 1 H, J(OH,3′) = 4.1 (3′-OH); 6.47 dd, J(1′,2a′)
= 5.7, J(1′,2b′) = 8.9 (H-1′); 7.12 s, 1 H and 7.19 s, 1 H (NH2); 7.85 s, 1 H (H-6); 8.37 t, 1 H,
J(NH,CH2) = 5.6 (NH); 10.82 bs, 1 H (H-3).
N,N-Dimethyl-3′,5′-di-O-benzoylthymidine-4′-C-carboxamide (13a)
1,1′-Carbonyldiimidazole (90 mg, 0.55 mmol) was added to a solution of acid 4 (246 mg, 0.5 mmol)
in dimethylformamide (2 ml). After standing at room temperature for 1 h, the solution was slowly
saturated with dimethylamine and the reaction was monitored by TLC. When the reaction was com-
plete, the solvent was evaporated and the residue was dissolved in ethyl acetate (20 ml). The solution
was washed with water (3 × 10 ml), dried over magnesium sulfate and the solvent was evaporated.
Column chromatography on silica gel (20 g) in ethyl acetate–toluene (3 : 1) afforded 182 mg (70%)
of compound 13a as a solid foam. For C27H27N3O8 (521.5) calculated: 62.18% C, 5.22% H, 8.06% N;
1
found: 61.91% C, 5.44% H, 7.85% N. H NMR spectrum: 1.65 s, 3 H (CH3); 2.50 dd, 1 H, J(2a′,1′) = 5.0,
J(2a′,2b′) = 13.7 (H-2a′); 2.75–2.90 m, 1 H (H-2b′); 2.85 s, 3 H (NCH3); 3.31 s, 3 H (NCH3); 4.81 d,
1 H, J(5a′,5b′) = 11.3 (H-5a′); 4.90 d, 1 H (H-5b′); 5.92 d, 1 H, J(3′,2b′) = 4.6 (H-3′); 6.51 dd, 1 H,
J(1′,2a′) = 5.0, J(1′,2b′) = 9.9 (H-1′); 7.49–7.72 m and 7.86–7.96 m, 7 H and 4 H (H-arom., H-6);
11.43 s, 1 H (H-3).
N,N-Dimethylthymidine-4′-C-carboxamide (13b)
Dibenzoyl derivative 13a (156 mg, 0.3 mmol) was methanolyzed with 0.1 M methanolic sodium
methoxide as described for compound 12b; yield 76 mg (81%) of dimethylamide 13b, m.p. 215–218 °C.
For C13H19N3O6 (313.3) calculated: 49.83% C, 6.11% H, 13.41% N; found: 49.61% C, 6.29% H,
1
13.20% N. H NMR spectrum: 1.78 s, 1 H (CH3); 2.01–2.35 m, 2 H (2 × H-2′); 2.83 bs, 3 H (NCH3);
3.11 bs, 3 H (NCH3); 3.64–3.86 m, 2 H (2 × H-5′); 4.37 t, 1 H, J(3′,2b′) = 3.7, J(3′,OH) = 4.0 (H-3′);
5.32 t, 1 H, J(OH,5′) = 5.5 (5′-OH); 5.44 d, 1 H, J(OH,3′) = 4.0 (3′-OH); 6.37 dd, 1 H, J(1′,2a′) = 5.5,
J(1′,2b′) = 9.5 (H-1′); 7.83 s, 1 H (H-6); 11.33 s, 1 H (H-3).
N-(2-Hydroxymethyl)-3′,5′-di-O-benzoylthymidine-4′-C-carboxamide (14a)
1,1′-Carbonyldiimidazole (90 mg, 0.55 mmol) was added to a solution of acid 4 (246 mg, 0.5 mmol)
in dimethylformamide (2 ml). After standing at room temperature for 1 h, the solution was slowly
added to a stirred solution of 2-aminoethanol (61 mg, 1 mmol) in dimethylformamide (1 ml). The
reaction mixture was set aside at room temperature for 3 h and the solvent was evaporated. The
residue was dissolved in ethyl acetate and the solution was washed with 5% hydrochloric acid, water,
5% solution of sodium hydrogen carbonate, dried and the solvent was evaporated. Column chroma-
tography on silica gel in ethyl acetate gave 190 mg (71%) of hydroxyethylamide 14a as a solid foam.
For C27H27N3O9 (537.5) calculated: 60.33% C, 5.06% H, 7.82% N; found: 60.05% C, 5.11% H,
7.56% N. 1H NMR spectrum: 1.68 s, 3 H (CH3); 2.51 dd, 1 H, J(2a′,1′) = 5.3, J(2a′,2b′) = 14.7
(H-2a′); 2.76 m, 1 H (H-2b′); 3.03–3.50 m, 4 H (CH2CH2); 4.70 d, 1 H (H-5a′); 4.73 t, 1 H,
Collect. Czech. Chem. Commun. (Vol. 62) (1997)

Thymidine-4’-C-carboxylic Acid
1135
J(OH,CH2) = 5.5 (CH2OH); 4.98 d, 1 H, J(5a′,5b′) = 11.6 (H-5b′); 5.87 d, 1 H, J(3′,2b′) = 4.3 (H-3′);
6.54 dd, 1 H, J(1′,2b′) = 9.3 (H-1′); 7.48–7.97 m, 11 H (H-6, H-arom.); 8.40 t, 1 H, J(NH,CH2) = 5.3
(NHCH2); 11.42 s, 1 H (H-3).
N-(2-Hydroxyethyl)thymidine-4′-C-carboxamide (14b)
Benzoyl derivative 14a (161 mg, 0.3 mmol) was methanolyzed in the same manner as described for
the derivative 12b; yield 84 mg (85%) of amorphous hydroxyethylamide 14b. For C13H19N3O7
1
(329.3) calculated: 47.41% C, 5.82% H, 12.76% N; found: 47.68% C, 6.01% H, 12.51% N. H NMR
spectrum: 1.78 s, 3 H (CH3); 2.02–2.27 m, 2 H (2 × H-2′); 3.01–3.43 m, 4 H (CH2CH2); 3.59–3.68 m,
1 H (H-5a′); 3.79–3.87 m, 1 H (H-5b′); 4.29 m, 1 H (H-3′); 4.60 t, 1 H, J(OH,CH2) = 5.6 (CH2OH);
5.30 t, 1 H, J(OH,5′) = 5.0 (5′-OH); 5.37 d, 1 H, J(OH,3′) = 4.6 (3′-OH); 6.40 dd, 1 H, J(1′,2a′) = 5.5,
J(1′,2b′) = 8.9 (H-1′); 7.78 t, J(NH,CH2) = 5.6 (NH); 7.87 s, 1 H (H-6); 11.32 s, 1 H (H-3).
The authors are indebted to Professor E. De Clercq and to Dr J. Balzarini (Rega Institut, Katholieke
Universiteit Leuven, B-3000 Leuven, Belgium) for antiviral activity assays. The excellent technical as-
sistance of Mrs A. Sterecova is gratefully acknowledged. The authors’ thanks are also due to Mrs M.
Snopkova for the NMR measurements and to the staff of the Analytical Laboratory (Dr V. Pechanec,
Head) of this Institute for elemental analyses. This study was supported by the Grant Agency of the
Czech Republic (Grant No. 203/94/0099).
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