CEPHALOSPORIN DERIVATIVES

The present invention relates to new cephalosporins and methods for their preparation. The invention also relates to the preparation of pharmaceutical preparations containing the cephalosporins and to methods for the pharmacological use of the cephalosporins. In particular this invention relates to a process for the preparation of compounds of the formula I or a pharmaceutically acceptable salt thereof, in which formula R1 is selected from the group consisting of a phenyl group, a thienyl group, a furyl group, a pyridinal group, and a tetrazolyl group, R2 is selected from the group consisting of a group S-R4 where R4 is an imidazolyl, benzoimidazolyl, benzothiazolyl, benzoxazolyl, thiadiazolyl or 5-methylthiadiazolyl group; a xanthate group; a dithiocarbamate group, an azido group; a hydrogen atom; an acetoxy group 1-pyridinium; R3 is selected from the group consisting of wherein R5 is a hydrogen atom or a methyl group; R7 is a lower alkyl group, a cycloalkyl group of 3 to 7 carbon atoms; a phenyl or naphthyl group; an aralkyl group such as benzyl or naphthylmethyl; and wherein the alkyl, cycloalkyl, aryl and aralkyl groups may be substituted with one or more groups selected from the class consisting of amino groups, methyl-amino, diethylamino and acetamido groups, fluorine, chlorine or bromine atoms, nitro groups, lower alkoxy groups, X1 is selected from the group consisting of O and S; Y1 is selected from the group consisting of a hydrogen atom; a hydroxy group; a bromine, chlorine, fluorine or iodine atom; an azido group; an amino group; a substituted amino group selected from methylamino, diethylamino, benzyl sulphenylamino, methoxy-(hydroxy)phosphinylamino and acetamido; n is 0 or 1, m is 0 or 1; characterized ina) reacting a compound of the formula or a salt thereof with a compound of the formula R3' - Y2 to form a compound of the formula in which formulae X1, R3, m and n have the meanings given above, Y2 is a halogen group or a functionally equivalent group thereof such as an organic sulphonic acid residue and R1', R2', and Y2' are R1, R2 and Y1 respectively as defined above or in case R1, R2 and Y1 contain amino or carboxy groups, protected derivatives of R1, R2 and Y1, whereafter, if necessary, the protecting groups are removed to give a compound of the formula I; orb) reacting a compound of the formula with a compound of the formula to form a compound of the formula in which formulae R1', X1, Y1', R2', R3', m and n are as defined above and -CO-Z