Cytosine analogue, a method of preparation of a cytosine analogue, a DNA methyltransferase 1 inhibitor, a method for DNA methylation inhibition, the use of the analogue in the treatment of diseases associated with deviations from normal DNA methylation

A method of preparation of an analogue of cytosine or a physiologically acceptable salt or a prodrug thereof, selected from the group consisting of 1, N4, 5 and 6 substituted derivatives of cytosine, 5-azacytosine, or 5,6-dihydrocytosine, wherein said analogue is described by the chemical formulas

• where
• R1 is H, R4, or 2′-deoxyribosyl,
• R4 is alkyl or aralkyl,
• X is N in formula I or II, or X is C in formula I,
• wherein with the proviso that if X in the analogue of formula I is N,
• then R5 is no substituent and,
• wherein with the proviso that if X in the analogue of formula I is C or if X in the analogue of formula II is N,
• then R5 and R6 are independently alkyl, aryl, hydroxyalkyl, aminoalkyl, hydroxyl, carboxyl, amino group, alkoxyl, aryloxyl, aminoalkyl, aminoaryl, thio group, sulfonyl, sulfinyl or halogen,
• wherein the method comprises:
• a) adding an N4-unsubstituted cytosine or an analogue thereof as defined above and an aromatic or an alkyl aldehyde in the quantity of 4-6 eq to anhydrous methanol or ethanol,
• b) introducing NaBH4 or BH3×SMe2 to the mixture in the amount of at least 1.1 eq relative to the aldehyde in order to reduce the obtained imine,
• c) neutralizing the reducing agent with hydrochloric acid,
• d) evaporating the mixture,
• e) pouring the mixture into water,
• f) extracting the mixture with ethyl acetate or butanol to obtain a mixture of alcohol and an N4-modified cytosine or an analogue thereof as defined above in ethyl acetate or butanol,
• g) obtaining a pure product by:
• evaporating the separated organic layer to dryness to obtain the pure product or;
• extracting the separated organic layer with aqueous solution of an inorganic acid to obtain an aqueous solution of cytosine hydrochloride or other modified said N4-modified cytosine salt, depending on the acid added, where the resulting salt is free of alcohol, further comprising
• 1) neutralizing the solution with a hydroxide or other hydroxyl group donor,
• 2) extracting the solution with ethyl acetate or butanol,
• 3) at least one of freeze drying, evaporating, or a combination thereof the organic layer to obtain the pure product.