- PROCEDURE FOR THE PREPARATION OF 4- [(2 ', 5' -DIAMINO-6 '-HALOPIRIMID N-4' -IL) AMINO] -CICLOPENT-2-ENYLENETHOLES FIELD OF THE INVENTION The present invention relates to a new process for the preparation of 4- [(2 ', 5' -diamino-6 '-halopyrimidin-4' -yl) amino] cyclopent-2-enylmetañóles of the general formula
2
BACKGROUND OF THE INVENTION / 4- [(2 5'-Diamino-6'-halopyrimidin-1-yl) amino] cyclopent-2-enylmethanols are important intermediates for the preparation of antiviral nucleotide derivatives (WO 91/01310) . The 3-step synthesis of 4- [(2 J 5 '-diamino-6' -halo? Irimidin-1-yl) amino] cyclopent-2-enylmethanols from 4-acetamidocyclopent-2-enylmethanol is known by means of reaction with 2-amino-4,6-dichloropyrimidine in butanol with diisopropylethylamine as the base. For this first the [(2"-amino-6 '-chloropyridimin-4" -l) amino] cyclopent-2-enylmethanol is formed, which then in a later stage is transformed by means of diazotization, in the corresponding amine , which is then hydrolysed to the final product (J. Chem. Soc. Perkin, Trans., 1, 1992) This procedure has the disadvantage that it is expensive and that the desired final product is only obtained with a moderate yield. OF THE INVENTION The task of the present invention is to present a 1-step procedure, and therefore more economical for the preparation of 4- [(2'-5'-diamino-6 '-halopyrimidin-4'-yl) ) amino] -cyclopent-2-enylmethanols, in which the desired products are obtained in good yields DESCRIPTION OF THE INVENTION That task is solved with the process according to claim 1. Surprisingly it was found that when instead of 2- amino-, 6-dichloropyrimidine as starting material, a 2, 5-dia is used mino-, 6-dihalopyrimidine of the general formula
H, N (II) and this is reacted in the presence of a base in a polar protic solvent with a 4-aminociclopent-2-enylmethanol of the formula
or with a salt thereof, the desired final product of the general formula is obtained
in a much more economical way and with a good performance. The substituent X means a halogen atom such as F, Cl, Br or I. 2, 5-diamino-, 6-dihalopyrimidine, as well as 2,5-diamino-4,6-dichloropyrimidine can be prepared according to EP-A-0 864 326. As 4-aminocilopent-2-enylmethanols, compounds can be used. both racemic and also optically active such as (1R, 4S) -, (1D, 4R) -, (1R, 4R) -, or (ls, 4s) -4-aminociclopent-2-enylmethanols. Suitable salts of these are the acid addition salts, especially the hydrohalogenide salts, for example the hydrochlorides and the bromohydrates. The 4-aminocyclopent-2-enylmethanols, especially the enantiomers (IR, 4S) - or (1S, 4R), can be prepared according to WO 97/45529. Advantageously, the reaction is carried out in the presence of an alkali metal or alkaline earth metal carbonate, an alkali metal or alkaline earth metal hydrocarbonate or in the presence of nitrogen bases, such as, for example, tertiary amines, as the base. As the alkali metal carbonate or alkali metal hydrocarbonate, sodium or potassium carbonate or sodium or potassium hydrocarbonate can be used. As the alkaline earth metal carbonate or alkaline earth metal hydrocarbonate, calcium or magnesium carbonate or calcium hydrocarbonate may be used. Suitable tertiary amines are, for example, triethylamine and diisopropylethylamine. Preferably, the reaction is carried out in the presence of an alkali metal hydrocarbonate such as sodium hydrocarbonate or in the presence of a tereamine, such as diisopropylethylamine. The base is advantageously used in an excess relative to 2, 5-diamino-4,6-dihalopyrimidine, preferably 1 to 4 moles of base are used per mole of 2,5-diamino-4,6-dihalopyrimidine. As the polar protic solvent, alcohols with 1 to 4 carbon atoms, such as methanol, are particularly suitable., ethanol, propanol and its isomers and butanol and its isomers. Advantageously, the reaction is carried out at a temperature of 20 ° C up to the reflux temperature of the corresponding solvent, preferably 50 ° C up to the reflux temperature. Advantageously, 4-aminociclopent-2-enylmethanol and 2,5-diamino-4,6-dihalopyrimidine are used equimolarly. After a reaction time of 2 to 20 hours the final products can then be obtained according to formula I, preferably (lS, 4R) -4- [(2 5'-diamino-6 '-halopyrimidin-4'I) ) amino] cyclopent-2-enylmethanol, by means of the usual processing methods. EXAMPLES Example 1 Preparation of 4- [(2 ', 5'-diamino-6'-chloropyrimidin-4'-yl) amino] cyclopent-2-enylmethanol in the presence of sodium hydrocarbonate Hydrochloride of (SS, 4R) -4 -aminocyclopent-2-enylmethanol (0.14 mol, 23.25 g), ethanol (3 mol, 138.12 g 176 ml), 2,5-diamino-4,6-dichloropyrimidine (0.14 mol, 25 g) and sodium hydrocarbonate (0.34 mol) , 28.68 g) were introduced to a dry reactor. This mixture was heated to reflux temperature (about 80 ° C) for 16 hours. The transformation rate was tested according to TLC (thin layer chrography) with 13/1 methylene chloride: methanol as eluent. The reaction mixture was cooled to room temperature and stirred for 45 minutes. The salts were removed by filtration and the filter cake was washed twice with ethanol (0.86 mol, 39.5 g, 50 ml). After 2/3 of the organic phase had been removed by distillation, it was added dropwise (150 ml) of hexane. The suspension was cooled to 10 ° C. After filtering, it is dried in vacuo at 50 ° C. 21.5 g (0.08 mol) of final product were obtained, corresponding to a yield of 60%. Example 2 Preparation of 4 [(2 J 5 '-diamino-6' -chloropyrimidin-4'-yl) amino] cyclo? Ent-2-enylmethanol in the presence of diisopropylethylamine Hydrochloride of (SS, 4R) -4-aminociclopent -2-enyl-methanol (0.14 mol, 23.18 g), butanol (1.26 mol, 93.39 g, 115.3 ml), 2,5-diamino-4,6-dichloropyrimidine (0.14 mol, 25.67 g) and diisopropylethylamine (0.29 g) mol, 37.09 g, 49.99 ml) are introduced into a dry reactor. This mixture was heated overnight at reflux temperature (about 115 ° C). The reaction rate was tested according to TLC with 13/1 methylene chloride: methanol as eluent. The reaction mixture was cooled to room temperature. Then water was added and then extracted twice with ethyl acetate. The organic phase was washed twice with water, and then the organic phase was filtered through Celite. After 2/3 of the organic phase was separated by vacuum distillation, hexane was added dropwise. The suspension was cooled to below 10 ° C. After filtering, it was dried under vacuum at 50 ° C. 21.47 g (0.08 mol) of final product were obtained, corresponding to a yield of 60%.