Specific inhibitors in vitamin biosynthesis. Part 11. Syntheses of pterins with extended side chains at C-6

In order to provide access to highly functionalised pterins as potential inhibitors of enzymes in the folate biosynthesis pathway, the Wittig reaction has been applied to 6-formylpterin (1b) and 6-formyl-7,7-dihydro-7,7-dimethylpterin (6). Dimethylaminomethylene and pivaloyl moieties were found to be suitable protecting groups for the 2-amino group of the pterins compatible with reactions of phosphoranes with a variety of substituents including esters, ethers and amides. In contrast, attempts to prepare extended side chains at C-6 using aldol and Claisen chemistry were unsuccessful.