A procedure for preparing nucleosides and analogues of nucleosides

Procedure for preparing nucleosides and analogues of nucleosides of the formula where A is X is O, S or CH2; R1 is H, alkyl of 1-3 carbons, -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, or -C[triple bond]CH; R2 is H or constitutes a carbon-carbon bond together with R3; and R3 is H, halogen, N3, CN, C=CH, OH, OCH3 or CH2OH, with R3 being able to have a cis or trans configuration, relative to the hydroxymethyl function, or with R3 constituting a carbon-carbon bond together with R2. This procedure involves condensing a glycoside included in formula I in the N-1 position of a pyrimidine derivative corresponding to an aforesaid radical A, separating the α-anomer of the compound I formed and eliminating any protecting group present. There are other methods of preparation which are described in the specification. The compounds obtained are useful for preventing and treating hepatitis B, AIDS and other infections in mammals. PROCEDIMIENTO PARA PREPARAR NUCLEOSIDOS Y ANALOGOS DE NUCLEOSIDOS DE FORMULA DONDE A ES X ES O, S O CH2; R1 ES HIDROGENO, ALQUILO DE 1-3 CARBONOS, -CH=CH2, -CH=CH-CH3, -CH2-CH=CH2, -C-=CH2-CH3 O -C=CH; R2 ES H O CONSTITUYE JUNTO CON R3 UN ENLACE CARBONO-CARBONO; Y R3 ES H, HALOGENO, N3, CN, C=CH, OH, OCH3 O CH2OH, PUDIENDO TENER R3 CONFIGURACION CIS O TRANS, CON RELACION A LA FUNCION HIDROXIMETILO O CONSTITUYENDO R3 JUNTO CON R2 UN ENLACE CARBONO-CARBONO. ESTE PROCEDIMIENTO COMPRENDE CONDENSAR UN GLICOSIDO INCLUIDO EN LA FORMULA (I) EN LA POSICION N-1 DE UN DERIVADO DE PIRIMIDINA CORRESPONDIENTE A UN RADICAL A ANTES CITADO, SEPARAR EL ANOMERO DEL COMPUESTO (I) FORMADO Y ELIMINAR CUALQUIER GRUPO PROTECTOR PRESENTE. EXISTEN OTRAS VIAS DE PREPARACION QUE SE DESCRIBEN EN LA MEMORIA. LOS COMPUESTOS OBTENIDOS SON UTILES PARA PREVENIR Y TRATAR HEPATITIS B, SIDA Y OTRAS INFECCIONES EN MAMIFEROS.