A total synthesis of 4-amino-L-erythro-biopterin(2) in a one-pot process is described, which comprises the following main steps: (a) oxidation of L-rhamnose diethylmercaptal (5) with H2O2/HCOOH to its bis-sulfone(6), (b) preparation of 5-deoxy-L-arabinose (7) through aminolysis of 6, (c) condensation of the protected 5-deoxy-L- arabinose (9) with tetraaminopyrimidine, (d) iodine oxidation of the formed tetrahydroaminobiopterin derivative (10) to 1', 2'-O-diacetyl- L-erythro-aminobiopterin (12) and purification of 12 using column chromatography, and (f) deacetylation of 12 with NH3-H2O/MeOH to give 2. Thus, the overall yield of 2 from 5 was 17%.

Key words: INHIBITOR, PTERIN, NITROGEN MONOXIDE, SYNTHETASE, TOTAL SYNTHESIS