| abstract |
Compounds of structure (I) <CHEM> in which, R<1> is hydrogen, C1-4alkyl, CHR<6>CONHR<7> or CHR<6>COOR<7> in which R<6> and R<7> are each hydrogen or C1-4alkyl; R<2> is hydrogen, C1-5alkyl or a residue R<2> of an amino acid R<2> CH(NH2)COOH; R<3> is hydrogen, C1-4alkyl, CONH2 or CO2R<8> in which R<8> is hydrogen or C1-4alkyl; and n is 2, 3 or 4, processes for their preparation, intermediates useful in their preparation, pharmaceutical composition containing them and their use in therapy as nootropic agents. |