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Abstract

The compounds of formula (I) ##STR1## wherein R.sup.1 is hydrogen, lower alkyl of 1-4 carbons, lower alkenyl of 2-4 carbons, --B--X--R.sup.5).sub.n, or --B--Z--B--X--R.sup.5 --.sub.n ; n=0 when X is halogen or n=1 when X is --O--, --NR.sup.6 -- (where R.sup.6 is hydrogen or lower alkyl of 1-4 carbons) or --S(O)q-- (where q=0 to 2); B is lower alkanyl (straight or branched) of 1-5 carbons; R.sup.5 is hydrogen, aralkyl of 7 to 12 carbons or alkyl of 1-10 carbons; Z is --O--, NR.sup.6 --, or --S(O)q--; R.sup.2 is hydrogen or lower alkyl of 1-4 carbons or lower alkenyl of 2-4 carbons or either R.sup.1 and R.sup.2 together with the carbon atom in the pteridine ring structures to which they are attached, form a spirocycloalkyl ring system having 3 to 7 carbon atoms; R.sup.3 and R.sup.4 are hydrogen or methyl; R.sup.2 and R.sup.3, together with the carbon atoms in the pteridine ring structure to which they are attached, form a cycloalkyl ring system having 5 to 7 carbon atoms; provided that at least one of R.sup.1, R.sup.2, R.sup.3 and R.sup.4 is hydrogen, and further provided that one of R.sup.1, R.sup.2 and R.sup.3, R.sup.4 represents gem disubstitution; have been found to selectively cofactor the biological conversion of tyrosine to dopamine, and are useful in the treatment of diseases resulting from a deficiency of dopamine in the brain such as Parkinson's disease. A further aspect of this invention comprises novel compounds of formula (I) defined above with the proviso that when both R.sup.3 and R.sup.4 are methyl neither R.sup.1 and R.sup.2 may be methyl, and R.sup.1 and R.sup.2 may not both be hydrogen, or a pharmaceutically acceptable salt thereof.

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First Claim