Novel 5-lower alkyl-2'-desoxyuridine-5'-monophosphates of the formula ##STR1## wherein R is lower alkyl of 2 to 6 carbon atoms having antiviral activity.

STATE OF THE ART 
Desoxyuridines having antiviral activity are known and 
5-iodo-2'-desoxyuridine (IDU) and 5-ethyl-2'-desoxyuridine (EDU) have been 
used in the clinical treatment of herpes diseases caused by Herpes Simplex 
Type 1 and 2 viruses (HSV-1 and HSV-2). Since it is known that 97% of the 
population have been infected with these herpes viruses with a high 
percentage experiencing an active infection and with a large proportion 
tending to suffer reoccurrences, it is of great importance to improve the 
available drugs. Another factor for the importance of the control of 
herpes infections caused by HSV-2 is that these viruses have an 
oncologenic action and are involved in the beginning of some forms of 
cancer. 
OBJECTS OF THE INVENTION 
It is an object of the invention to provide the novel monophosphates of 
formula I and to provide a novel process for their preparation. 
It is another object of the invention to provide novel antiviral 
compositions and to provide a novel method of combatting antiviral 
infections in warm-blooded animals, especially herpes infections. 
These and other objects and advantages of the invention will become obvious 
from the following detailed description. 
THE INVENTION 
The novel monophosphates of the invention have the formula 
##STR2## 
wherein R is lower alkyl of 2 to 6 carbon atoms. 
As indicated by the waved lines in the above formula I connecting the 
nitrogen atom in the 8 position of the uracil residue and a hydrogen atom 
respectively with the carbon atom in the 1 position of the sugar moiety, 
the monophosphates of the invention can exist in two anomeric forms. These 
are the .alpha.- and .beta.-anomers, which differ from each other only by 
the steric arrangement of said uracil residue on carbon atom 1 of the 
sugar moiety. The invention comprises both the separate .alpha.- and 
.beta.-anomers of the monophosphates of formula I as well as the mixtures 
thereof. 
Examples of suitable alkyls for R are those of 2 to 6 carbon atoms, 
preferably 2 to 4 carbon atoms such as ethyl, propyl, isopropyl, butyl, 
isobutyl, pentyl and hexyl. 
The novel process of the invention for the preparation of the compounds of 
formula I comprises reacting a 5-lower alkyl-2'-desoxyuridine with an 
acetylation agent using the procedure of Michelson et al [J. Chem. Soc., 
1953, p. 951] to obtain 5-lower alkyl-3'-acetyl-2'-desoxyuridine, reacting 
the latter with .beta.-cyanoethyl phosphate by the method of Tener 
[J.A.C.S., Vol. 83 (1961) p. 159] to obtain 5-lower 
alkyl-2'-desoxyuridine-5'-monophosphate. 
More specifically, the novel process of the invention for the preparation 
of the compounds of formula I comprises 
(a) reacting a 5-lower-alkyl-2'-desoxyuridine of the formula 
##STR3## 
wherein R is as defined above, with a triphenylmethyl halide, preferably 
triphenylmethyl chloride, in an organic solvent, preferably pyridine, 
under anhydrous conditions to form the corresponding triphenylmethyl 
derivative, 
(b) reacting said triphenylmethyl derivative in an organic solvent, 
preferably in pyridine, under anhydrous conditions with an acetylating 
derivative of acetic acid, preferably acetic anhydride, for form an 
acetylated product, 
(c) subsequently heating said acetylated product in an organic solvent, 
preferably acetic acid, to form the corresponding 5-lower 
alkyl-3'-acetyl-2'-desoxyuridine of the formula 
##STR4## 
wherein R is as previously defined, 
(d) reacting the latter product with an organic solution of 
.beta.-cyanoethyl phosphate, preferably a pyridine solution, in the 
presence of dicyclohexyl carbodiimide as a condensing agent, 
(e) removing the cyanoethyl group by mild hydrolysis, preferably mild 
alkaline hydrolysis, and 
(f) separating the desired product. 
The preparation of the 5-lower alkyl-2'-desoxyuridine starting materials is 
described in German published patent application No. 1,620,185. 
More specifically, the 5-lower alkyl-2'-desoxyuridines are prepared by 
reacting the corresponding 5-lower alkyl uracils or their mercury salts 
with the corresponding optionally protected desoxyribose derivative in a 
manner known per se. For example, the mercury salt of the uracil 
derivative may be reacted with a protected halogenated desoxy ribose 
compound. The thus obtained protected 5-lower alkyl uracils are a mixture 
of the .alpha.- and .beta.-anomers. If desired, the two anomeric forms of 
the protected product may be separated completely or partially by 
crystallization from various solvents, e.g. toluene or diethyl ether. 
Thereafter the protective group is selectively cleaved off, e.g. with 
sodium methylate or methanolic ammonia, in a known manner. 
The separated .alpha.- and .beta.-anomers of the 5-lower 
alkyl-2'-desoxyuridines as starting materials of the present process yield 
the corresponding .alpha.- and .beta.-anomer forms respectively of the 
5-lower alkyl-2'-desoxyuridine-5'-monophosphates of the invention, whereas 
a mixture of the .alpha.- and .beta.-anomers of the starting 5-lower 
alkyl-2'-desoxyuridines yields a corresponding .alpha.- and .beta.-anomer 
mixture of the desired end product. 
The compounds for the preparation of the starting materials are either 
known or may be readily prepared by known processes. 
The novel antiviral compositions of the invention are comprised of an 
antivirally effective amount of at least one compound of formula I and an 
inert pharmaceutical carrier or excipient. The compositions may be in the 
form of tablets, coated tablets, dragees, gelules, granules, suppositories 
and injectable solutions or suspensions and may contain one or more other 
antiviral agents. 
Examples of suitable excipients are talc, lactose, starch, magnesium 
stearate, cocoa butter, aqueous and nonaqueous vehicles, fatty bodies of 
animal or vegetable origin, paraffinic derivatives, glycols, diverse 
wetting agents, dispersants or emulsifiers and preservatives. 
The compositions are useful for combatting viral infections, especially 
those of the herpes type such as HSV-1 and HSV-2. The compositions have 
been found to have antiviral activity against herpes which is clearly 
superior to 5-ethyl-2'-desoxyuridine (EDU) and are effective against 
EDU-resistant viruses. 
The .alpha.-anomer of 5-ethyl-2'-desoxyuridine-5'-monophosphate exhibits an 
additional, surprising property in that it inhibits the reproduction of 
Herpes Simplex Viruses. In tissue cultures of chicken embryo fiberblasts 
this compound significantly inhibits the virus reproduction at a 
concentration of 10 .mu.g/ml. Under the same conditions the .alpha.-anomer 
of 5-ethyl-2'-desoxyuridine is ineffective. Further, the .alpha.-anomer of 
5-ethyl-2'-desoxyuridine-5'-monophosphate surprisingly has virostatic 
activities, but surprisingly is not built into the desoxyribonucleic acid 
(DNS), which completely rules out any potential genetic risk. 
The novel method of preventing or treating viral infections in warm-blooded 
animals, including humans, comprises administering to warm-blooded animals 
an antivirally effective amount of at least one compound of formula I. The 
compounds may be administered orally, rectally, or parenterally and the 
usual daily dose is 5 to 300 mg/kg depending upon the compound and method 
of administration. The method is particularly effective against herpes 
viruses.

In the following examples there are described several preferred embodiments 
to illustrate the invention. However, it should be understood that the 
invention is not intended to be limited to the specific embodiments. 
PREATION OF THE STARTING COMPOUNDS 
Preparation A 
5-Ethyl-2'-desoxyuridine 
0.01 moles mono-(5-ethyluracilyl)mercury and 0.02 moles 
di-p-chlorobenzoyl-desoxyribofuranosyl chloride are heated under stirring 
in 150 ml anhydrous toluene until reflux temperature, forming a clear 
solution. After distilling off the toluene the residue is taken up in 100 
ml chloroform and shaken with 30% potassium iodide solution to eliminate 
the mercury ions. Petrol ether with boiling point 50.degree. to 70.degree. 
C. is added to the organic phase and the crystallized product is filtered 
off. 
Thereafter the product is kept under reflux with a 2% sodiummethylate 
solution in absolute methanol for two hours to desacylate. After 
distilling off the methanol the residue is treated with a cation exchanger 
in aqueous solution to eliminate the sodium ions. The mixture is extracted 
with diethylether and the aqueous solution is evaporated to dryness under 
vacuum. 5-ethyl-2'-desoxyuridine with melting point 154.degree. to 
157.degree. C. is obtained. 
______________________________________ 
Elemental analysis C.sub.11 H.sub.16 N.sub.2 O.sub.5 M.W. 256.26 
C H N 
______________________________________ 
calc.: 51.55 6.29 10.93% 
found: 51.32 6.41 10.53% 
______________________________________ 
Preparation B 
5-Ethyl-2'-desoxyuridine (alternate procedure) 
1.8 g mono-(5-ethyluracilyl)-mercury are heated in 70 ml absolute toluene 
under stirring and with a bath temperature of approximately 130.degree. C. 
for about 1 hour using a water separator. During this time approximately 
22 ml toluene are distilled off. 
The mixture is allowed to cool and 4.0 g 
3,5-di-p-tolyl-2-desoxy-D-ribofuranosyl chloride are added. Thereafter the 
heating is continued for another 40 minutes, during which time 
approximately 8.5 ml toluene are distilled off. 
After cooling the insolubles are sucked off, the filtrate is treated with 
30 ml of a 15% aqueous potassium iodide solution, the layers are separated 
and the organic layer is washed with 20 ml of water. After repeating the 
separation the toluene layer is dried over a drying agent. After standing 
over night, the drying agent is filtered off, washed with little absolute 
diethylether and to the filtrate approximately 60 ml n-hexane are added 
until the solution becomes permanently cloudy. The mixture is allowed to 
stand over night at room temperature and thereafter 5 hours in a deep 
freezer. 
The formed precipitate is sucked off, washed with n-hexane and finally 
dried in a vacuum desiccator. Yield: 1.15 g light brownish crystals with 
melting point 195.degree. to 197.degree. C. The filtrate is additioned 
with another 120 ml n-hexane and after standing for 3 days the initially 
oily precipitate is sucked off. It is washed with n-hexane and dried in a 
vacuum desiccator. 
Yield: 0.62 g slightly brownish crystals with melting point 120.degree. to 
175.degree. C. These are a mixture of two substances, as evidenced by thin 
layer chromatography using benzene:chloroform:acetone 5:4:1 on silicagel 
as the carrier. 
The initially precipitated reaction product (1.15 g) is nearly pure 
according to chromatography. For further purification it is recrystallized 
from 180 ml ethanol with activated charcoal additioned with some 
cellulose. The mixture is allowed to stand in the deep freezer over night, 
the formed precipitate is sucked off and dried in a vacuum desiccator. 
Yield: 1.05 g colourless crystals with melting point 198.degree. C. 
______________________________________ 
Elemental analysis C.sub.27 H.sub.28 N.sub.2 O.sub.7 M.W. 492.54 
C H N 
______________________________________ 
calc.: 64.83 5.73 5.68% 
found: 65.59 5.53 5.41% 
______________________________________ 
Based on NMR spectroscopic investigation the product consists of the 
.beta.-anomer. 
To 1 g of the above compound in 20 to 30 ml of absolute methanol 3 to 5 ml 
of a 1 N sodium methylate solution is added and the mixture is heated 
under reflux and under anhydrous conditions for approximately 1 hour. 
After completion of the reaction the methanol is distilled off in vacuo 
and the residue is additioned with approximately 7 ml of water. By adding 
a cation exchanger resin (H-form) and short shaking the solution is 
neutralized and after filtration the neutral, colourless solution is 
evaporated to dryness under vacuum. The residue is taken up in 20 to 25 ml 
of water, extracted 3 times with 5 ml each of methylen chloride and 
concentrated again in vacuo. The obtained crude nucleoside is dried again 
by azeotropic distillation with benzene/absolute ethanol. Thereafter the 
product is crystallized by adding absolute diethylether. 
Yield: 0.3 g product with melting point 156.degree. C. 
The .alpha.-anomer has a melting point of 178.degree. C. 
Preparation C 
5-Propyl-2'-desoxyuridine 
To a solution of 15,4 g 5-propyluracil (0.1 mole) and 21,7 g trimethylsilyl 
chloride (0,2 mole) in 250 ml anhydrous benzene 20.2 g dry triethylamine 
(0,2 mole) are added dropwise under stirring and exclusion of humidity 
within a time span of 15 minutes. After further stirring for about 12 
hours the unreacted 5-propyl-uracil and the precipitated dry ethylamine 
hydrochloride are separated and the filtrate is concentrated under vacuum. 
The residue is dissolved in 150 ml of absolute toluene and under stirring 
a solution of 43 g 3,5-di-(p-chlorobenzoyl)-2-desoxy-D-ribofuranosyl 
chloride (0,1 mole) in 500 ml toluene and thereafter 31,8 g mercury 
(II)-acetate are added and the stirring is continued another 24 hours. 
After filtration the filtrate is extracted with a 30% aqueous potassium 
iodide solution and thereafter washed with water. After drying over sodium 
sulfate the toluene solution is concentrated to approximately 100 ml. Upon 
standing the protected nucleoside crystallizes. 45 g of a product with 
melting point 140.degree.-165.degree. C. are obtained. 
Yield: 82% of the theoretical yield. 
This product is a mixture of the p-chlorobenzoyl-protected .alpha.- and 
.beta.-anomers. After one crystallization from toluene 28 g of a product 
are obtained which melts completely at 184.degree. C. This substance 
consists of approximately 90% .beta.-anomer. By further recrystallization 
no complete separation from the .alpha.-nucleoside could be achieved. 
The combined toluene filtrates are concentrated under vacuum to a sirupy 
consistency and thereafter additioned with approximately 150 ml ether. 
After prolonged standing in a refrigerator a second crop of 14 g of the 
anomer mixture with melting point 135.degree.-154.degree. C. are obtained. 
Upon recrystallization with ether the .alpha.-anomer with melting point 
139.degree.-142.degree. C. is obtained. 
According to thin layer chromatography this product still contains some 
.beta.-product. 
5,47 g of the above .beta.-product melting at 184.degree. C. are additioned 
with a solution of 3 ml of a 2% sodium methylate solution in 100 ml 
methanol and the mixture is heated under reflux for 90 minutes. Further 
work-up according to preparation A yields 2,0 g propyldesoxyuridine with 
melting point 162.degree.-163.degree. C. 
In the UV-spectrum the maximum (266 .mu.m) is shifted neither in alkaline 
nor in acidic medium. This confirms that the substituent is on the 
nitrogen atom at the 3 position. 
EXAMPLE 1 
5-ethyl-2'-desoxyuridine-5-monophosphate 
2 g of 5-ethyl-2'-desoxyuridine were reacted with triphenylmethyl chloride 
to obtain 4.1 g (75% yield) of the corresponding triphenylethyl derivative 
melting at 180.degree. C. which was then reacted with acetic anhydride to 
obtain 1.8 g (75% yield) of 5-ethyl-3'-acetyl-2'-desoxyuridine melting at 
150.degree. C. which was analytically pure. 
A mixture of 0.3 g (0,001 mole) of 5-ethyl-3'-acetyl-2'-desoxyuridine, 1.2 
g of dicyclohexylcarbodiimide and 2 ml of a pyridine solution of 0.002 
mole of .beta.-cyanoethyl phosphate were reacted to obtain 200 mg (62% 
yield) of 5-ethyl-2'-desoxyuridine-5'-monophosphate with an Rf=0.17 [1-7-2 
ammonia-isopropanol-water mixture]. 
U.V. Spectrum: pH=3.8 .lambda..sub.min 234, e=1745; pH=3 .lambda..sub.max 
267, e=7755. 
Using the same procedure, the 5-monophosphates of 
5-propyl-2'-desoxyuridine, 5-butyl-2'-desoxyuridine, 
5-pentyl-2'-desoxyuridine and 5-hexyl-2'-desoxyuridine were prepared. 
EXAMPLE 2 
A gel was prepared containing 1 g of polyacrylic acid, 2 g of 
5-ethyl-2'-desoxyuridine-5'-monophosphate, 2 mg of sodium ethyl mercuric 
thiosalicylate, sufficient sodium hydroxide for a pH of 7 and sufficient 
demineralized water for a final weight of 100 g. 
A second gel was prepared containing 2 g of methyl-cellulose, 1 g of 
5-propyl-2'-desoxyuridine-5'-monophosphate, 0.01 g of benzalkonium 
chloride, 0.1 g of sodium ethylenediaminetetraacetate and sufficient 
demineralized water for a final weight of 100 g. 
The preferred compositions of the invention are in the form of aqueous 
solutions, ointments, or gels containing 0.1 to 15% by weight, preferably 
0.1 to 10%, of the active compound of formula I. Suitable thickening 
agents are carboxymethylcellulose, polyvinylpyrrolidone or polyacrylic 
acid. 
PHARMACOLOGICAL DATA 
A. Antiviral Activity 
The antiviral activity of 5-ethyl-2'-desoxyuridine-5'-monophosphate and 
5-ethyl-2'-desoxyuridine was compared with 7 groups of six rabbits. The 
right cornea of each rabbit was scratched and was infected with Herpes 
Simplex Virus Type 1. Three groups of rabbits were treated with 
5-ethyl-2'-desoxyuridine (EDU) at concentrations of 1.2, 2.5 and 8% while 
3 other groups were treated with 5-ethyl-2'-desoxyuridine-5'-monophosphate 
(EDU-MP) at concentrations of 1.2, 2.5 and 8%. The seventh group served as 
a control group and the results are reported in FIG. 1. 
The results of FIG. 1 clearly show the superior antiviral activity of the 
monophosphate of the invention since on the sixth day the corneas of all 
the rabbits treated with the 8% concentration of EDU-MP were healed after 
6 days while with the rabbits treated with the 8% concentration of EDU, 
only the cornea of 5 out of 6 rabbits were healed after 8 days. 
To demonstrate the superiority of EDU-MP over EDU with EDU resistant 
viruses, the above test was repeated with three sets of 6 rabbits, one set 
as controls and one set treated with a solution of 2% of EDU and a third 
set treated with a solution of 1% of EDU-MP and the results are reported 
in FIG. 2. The results of FIG. 2 show that with progressive treatment of 
the infected rabbit cornea with the 1% concentration of EDU-MP, there is a 
strong inhibition of the infection while the infection progresses when 
treated with a 2% concentration of EDU under the same conditions. 
B. Cornea Compatibility 
To demonstrate the compatibility of EDU and EDU-MP with rabbit cornea, a 
wound of 50 mm.sup.2 was produced on the cornea of test rabbits and the 
process of the healing was determined by the reduction in size of cornea 
damage over a period of 11 days. Control rabbits received a daily 
treatment with just a solution of 0.90% sodium chloride while the test 
rabbits received a daily treatment with a solution containing 5% or 8% of 
EDU or EDU-MP and the results are shown in FIG. 3. 
In all cases, the healing process was completed no later than the 13th day. 
Treatment with EDU monophosphate did not substantially interfer with the 
healing process while the EDU treatment appeared to slow the healing 
process somewhat. 
Various modifications of the products and processes of the invention may be 
made without departing from the spirit or scope thereof and it is to be 
understood that the invention is intended to be limited only as defined in 
the appended claims.