5-Deoxy-L-arabinose (IV) is produced in high yield and at low cost by oxidizing L-rhamnose dialkylmercaptal (I) with hydrogen peroxide in an acetic acid solvent, followed by decomposing the resulting oxidationproducts with ammonia.
The 5-deoxy-L-arabinose produced is useful as a starting material for synthesizing L-erythro-5,6,7,8-tetrahydrobi- opterin.