Syntheses of optically active monapterin, 7,8-dihydromonapterin, and 5,6,7,8-tetrahydromonapterin from l-xylose.

We describe the syntheses of monapterin, dihydromonapterin and tetrahydromonapterin in optically active forms. The syntheses involved the condensation of l-xylose with phenylhydrazine, providing a hydrazone derivative. The reaction of the resulting hydrazone with triamino-pyrimidinone followed by oxidation of the resulting pteridinone with molecular oxygen furnished pterin containing a hydroxylated side chain. Hydrogenation of the pterin derivatives over RANEY® Ni catalyst afforded dihydromonapterin and tetrahydromonapterin in optically active forms. We also investigated an alternative route involving an Amadori rearrangement, followed by the Polonovski-Boon reaction as the key step to make these monapterin derivatives.