8-[(3R)-3-aminopiperidin-1-yl]-7-but-2-ynyl-3-methyl-1-[(4-methylquinazolin-2-yl)methyl]purine-2,6-dione
8-[(3R)-3-amino-1-piperidyl]-7-but-2-ynyl-3-methyl-1-[(4-methylquinazolin-2-yl)methyl]purine-2,6-dione
8-[(3R)-3-amino-1-piperidinyl]-7-but-2-ynyl-3-methyl-1-[(4-methyl-2-quinazolinyl)methyl]purine-2,6-dione
8-[(3R)-3-amino-1-piperidyl]-7-but-2-ynyl-3-methyl-1-[(4-methylquinazolin-2-yl)methyl]xanthine