Studies on 6-Methyl-5-deazatetrahydropterin and Its 4a Adducts

The oxidation properties of 6-methyl-5-deazatetrahydropterin (2) have been examined. The compound (2) reacts with a variety of electrophilic reagents (including A’-halosuccinimide, bromine, peroxy acid, and singlet oxygen) to generate the corresponding 4a adduct. These adducts (3-6) are characterized by their spectral properties (¹H and ¹³C NMR, UV) and analytical data. The aqueous-solution chemistry of the adducts is a function of the nature of the 4a substituent. The bromo and chloro adducts are readily reduced (and the former compound is an active brominating agent), while the hydroxy adduct undergoes a facile decomposition with rupture of the pyrimidine ring. The compound 2 is a competitive inhibitor of both phenylalanine and tyrosine hydroxylases, whereas the 4a adducts (3-6) show no apparent interaction with the enzyme.