The present disclosure relates to substituted quinazolines of formula (I) wherein X and Y are defined as in claim 1, the tautomers, stereoisomers, mixtures and salts thereof, which have valuable pharmacological properties, particularly an inhibitory effect on the activity of the enzyme dipeptidylpeptidase-IV (DPP-IV). In one embodiment the compound is 8-[(3R)-3-amino-1-piperidinyl]-1-[[4-[[2-[[8-[(3R)-3-amino-1-piperidinyl]-7-(2-butynyl)-2,3,6,7 -tetrahydro-3-methyl-2,6-dioxo-1H-purin-1-yl]methyl]-1,4-dihydro-4-methyl-4-quinazolinyl]methyl]-2-quinazolinyI]methyl]-7-(2-butynyl)-3,7-dihydro-3-methyl-1H-purine-2,6-dione.
