Bicyclic pyrimidines

Bicyclic pyrimidine compounds selected from those of formula I:

• ##STR16## wherein:
• T and U, which are the same or different, each represents a --CH-- radical or a nitrogen atom so as to form with the pyrimidinyl group a heterocycle selected from:
• purine, pyrazolo[3,4-d]pyrimidine, and 1,2,3-triazolo[4,5-d]pyrimidine;
• R and R', which are the same or different, each represents an alkyl radical having 1 to 5 carbon atoms inclusive or an alkenyl radical having 2 to 5 carbon atoms inclusive, each in straight or branched chain;
• A represents a heteromonocyclic radical of formula:
• ##STR17## wherein:
• B represents a radical of formula:
• ##STR18## wherein R" is a hydrogen atom or an alkyl radical having 1 to 5 carbon atoms inclusive in straight or branched chain and
• t represents an integer of 1 to 3;
• inclusive
• p is zero or one;
• X and Y, which are the same or different, each represents a hydrogen atom, a halogen atom, or an alkyl or alkoxy radical each having 1 to 5 carbon atoms inclusive in straight or branched chain;
• m and n, which are the same or different, each represents an integer of 1 to 3 inclusive;
• R.sub.1 and R.sub.2, which are the same or different, each represents a hydrogen atom or an alkyl radical having 1 to 5 carbon atoms inclusive in straight or branched chain, or together represent a single bond, an oxygen or sulphur atom, a radical --(CH.sub.2).sub.r -- in which r represents an integer of 1 to 3inclusive, a radical --CH.dbd.CH--, --O--CH.sub.2 --, --S--CH.sub.2 --, --SO.sub.2 --CH.sub.2 --, or --CO-CH.sub.2 --,
• R.sub.3 represents a hydrogen atom or a phenyl radical;
• and the chiral compounds and their enantiomers, and their physiologically tolerable salts with appropriate acids.