Abstract: A composition for use in the treatment of heart failure of mammals which comprises, as its active ingredient, an N.sup.6 -substututed-adenosine-3',5'-cyclic phosphate represented by the following general formula (I) or a physiologically acceptable salt thereof: ##STR1## wherein R represents alkyl or aralkyl group and a pharmaceutically acceptable carrier, as well as a method for treating heart failure of mammals which comprises administering said composition.

Abstract: A method for the preparation of an N.sup.6 -substituted 3',5'-cyclic adenosine monophosphate or a salt thereof represented by the general formula ##STR1## wherein R.sub.1 represents a straight chain or branched chain alkyl group of 1 to 13 carbon atoms or an aromatic group and B.sym. represents a hydrogen ion or an alkali metal ion, which comprises allowing a 3',5'-cyclic adenosine monophosphate or a salt thereof represented by the general formula ##STR2## wherein A.sym. represents a hydrogen ion, alkali metal ion, organic ammonium ion, or ammonium ion, to react with an aldehyde represented by the general formulaR.sub.1 CHO (III)wherein R.sub.1 is as defined above, under the conditions such that pH is 7.0 or below, the temperature is -10.degree. to 120.degree. C., and the molar ratio of the compound (II) to the compound (III) is 1:1-40, and reducing the resulting compound with a metal hydride or nascent hydrogen.

Abstract: A method for preparing an N.sup.6,8-disubstituted 3',5'-cyclic adenosine monophosphate or a salt thereof represented by the general formula ##STR1## wherein X denotes a halogen atom or ##STR2## N.sub.3, OH or OR, R being an alkyl or aralkyl group; A.sup..sym. denotes a hydrogen ion, alkali metal ion, ammonium ion or organic ammonium ion; and R.sub.1 denotes an alkyl or aromatic group, which method comprises reacting an 8-substituted 3',5'-cyclic adenosine monophosphate or a salt thereof represented by the general formula (II) ##STR3## wherein X and A.sup.61 are as defined above, with an aldehyde represented by the general formulaR.sub.1 --CHO (III)wherein R.sub.1 is as defined above, to form an imine compound represented by the general formula ##STR4## wherein X, R.sub.1 and A.sup..sym. are as defined above, as an intermediate, and then reducing the imine compound.