SYNTHESIS OF AMINO-6-CHLORO-2-PIPERAZINO-4-PYRROLIDINOPTERIDINE AND NOVEL DERIVATIVES FREE OF POSITIONAL ISOMERS - POTENT INHIBITORS OF CAMP-SPECIFIC PHOSPHODIESTERASE AND OF MALIGNANT-TUMOR CELL-GROWTH

amino-6-chloro-2-piperazino-4-pyrrolidinopteridine (7a) is a potent in hibitor of the cAMP-specific phosphodiesterase isoenzyme family PDE4 a nd induces growth inhibition in a panel of tumor cell lines. In this s tudy, we describe a synthesis that yields 7a and novel derivatives fre e of positional isomers. The synthesis of alkylamino substituted pteri dines is based on the successive nucleophilic aromatic substitution of the chlorine atoms of 2,4,6,7-tetrachloropteridine. For the reaction with secondary amines, the positional order of reactivity was found to be C4 > C7 > C2 > C6. Final structural proof is given by X-ray crysta llography. To unravel structural elements of 7a crucial for the intera ction with the target enzyme, the compound was modified systematically . The impact of the modifications on activity was tested by evaluating the ability of the compounds to inhibit cAMP hydrolysis by cAMP-speci fic phosphodiesterase (PDE4) purified from the solid human large cell lung tumor xenograft LXFL529. Growth inhibitory properties were determ ined by in vitro treatment of the respective cell line LXFL529L using the sulforhodamine B assay(SRB). The results show that for high activi ty, the heterocyclic substituent in position 2 of the pteridine ring s ystem requires the presence of a basic nitrogen in 4'-position, as rep resented by piperazine.