Abstract: Novel 6-heterocyclyl-pyrazolo[3,4-d]pyrimidin-4-ones, useful in treating cardiovascular disease, are prepared by reacting a 5-amino-1H-pyrazole-4-carboxamide with heterocyclyl-carboxaldehyde or by reacting a 5-amino-1H-pyrazole-4-carbonitrile with a heterocyclylcarboxamidine, followed by diazotization and hydrolysis of the resulting 4-amino-6-heterocyclyl-pyrazolo[3,4-d]pyrimidine.

Abstract: A method of inhibiting mammalian topoisomerase II and inhibiting the growth and inducing the regression of malignant cells in mammals by the action of a (S)-3-methyl-7-oxo-2,3-dihydro-7H-pyrido[1,2,3-de][1,4]benzoxazine or -benzothiazine of the formula ##STR1## wherein R.sub.1 is hydrogen or fluoro, R.sub.2 and R.sub.3 each independently is hydrogen or alkyl having 1 to 4 carbon atoms, and X is O, S or S=O; a pharmaceutically acceptable acid-addition salt thereof; or a salt thereof with a pharmaceutically acceptable cation; and certain novel compounds of formula I.

Abstract: Novel 6-heterocyclyl-pyrazolo[3,4-d]pyrimidin-4-ones, useful in treating cardiovascular disease, are prepared by reacting a 5-amino-1H-pyrazole-4-carboxamide with heterocyclylcarboxaldehyde or by reacting a 5-amino-1H-pyrazole-4-carbonitrile with a heterocyclylcarboxamidine, followed by diazotization and hydrolysis of the resulting 4-amino-6-heterocyclyl-pyrazolo[3,4-d]pyrimidine.

Abstract: 1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-ones having an aryl or heteroaryl group in the 6-position, useful as phosphodiesterase inhibitors, are prepared by reacting a 2-amino-5-(aryl or heteroaryl)pyridine-3-carboxylic acid with diphenylphosphoryl azide. The compounds are of the formula ##STR1## where R.sub.1 and R.sub.3 are hydrogen or lower-alkyl, R.sub.5 is lower-alkyl or fluorinated lower-alkyl, and Ar is 4-or 3-pyridinyl, or N-oxides thereof, or phenyl or substituted phenyl.