Lipoidal biopterin compounds

" The present invention provides lipoidal biopterin and tetrahydrobiopterin compounds of the general structure: ##STR1## wherein --R is absent when ring B has two double bonds, PA0 --R is hydrogen when the two double bonds in ring B are absent, and PA0 --R' and R"" are selected from saturated or unsaturated, cyclic or non-cyclic hydrocarbons of 1 to 31 carbon units. The compounds provided by this invention are oil soluble and can readily be formulated as an oil based pharmaceutical useful for the treatment of phenylketonuria, Parkinsonism, depression, senile dementia, Alzheimer's disease and related biopterin deficiency diseases. "