A Substituted 5-benzyl-2,4-diaminopyrimidines are used in combating or preventing infectious diseases, as described, for example, in EP-A 0 793 656.
The present invention provides substituted 5-benzyl-2,4-diaminopyrimidines of the formula 
in which
R1 is C2-C3 alkyl;
R2 denotes phenyl, naphthyl or heterocyclyl bonded via one of its C atoms, wherein phenyl, naphthyl or heterocyclyl can be mono- or polysubstituted; and
R3 represents C2-C6 alkyl, C2-C6 alkenyl, cycloalkyl, cycloalkylalkyl, heterocyclylalkyl, alkylsulphonyl, phenylsulphonyl, cycloalkylsulphonyl, cycloalkylalkylsulphonyl, cycloalkylalkylsulphamoyl, heterocyclylsulphonyl, heterocyclylalkylsulphonyl or dialkylsulphamoyl, wherein these groups can be unsubstituted or substituted,
and acid addition salts of these compounds.
The compounds of the present invention are useful as antibacterial agents.
The present invention also provides a pharmaceutical composition comprising a compound of formula A and a carrier.
The present invention also provides a pharmaceutical composition comprising a compound of formula A, a sulphonamide compound, and a carrier, wherein the ratio in parts by weight of the compound of formula A to sulphonamide is between 1:40 and 1:1.
In addition, the present invention provides a process for the preparation of a compound of formula A according to claim 1, comprising
a) reacting a compound of the formula 
with a compound of the formula:
R2Yxe2x80x83xe2x80x83C
in which R1, R2 and R3 have the meaning according to claim 1, wherein any phenolic hydroxyl groups and amino/alkylamino groups present are protected, one of the symbols X and Y represents a leaving group and the other represents a group which withdraws with this leaving group,
protective groups present are split off and, optionally, aromatic substituents on R2/R3 are derivatized, or
b) reacting a compound of the formula 
with a compound of the formula
R3Zxe2x80x83xe2x80x83E
in the presence of a base,
wherein any phenolic hydroxyl groups and amino/alkylamino groups present are protected and Z represents a leaving group,
protective groups present are split off and, optionally, aromatic substituents on R2/R3 are derivatized, and optionally, either or both of the following steps:
to prepare compounds of the formula A wherein R2 and/or R3 has a sulphonyl group xe2x80x94SO2xe2x80x94, a corresponding compound wherein R2 and/or R3 has a corresponding sulphanyl group xe2x80x94Sxe2x80x94 or sulphinyl group xe2x80x94SOxe2x80x94, is subjected to an oxidation,
converting a compound of the formula A into a pharmaceutically acceptable acid addition salt