Uridine 5'-phosphoramidate (I) was allowed to react with α-glucuronic acid 1-phosphate (II), and α-uridine diphosphate glucuronic acid (α-UDPGA) (III) was isolated from the reaction mixture by ion exchange chromatography. Likewise, β-UDPGA (V) was produced from (I) and β-glucuronic acid 1-phosphate (IV). Formation of (III) was also observed by the oxidation of α-uridine diphosphate glucose (VI) in the presence of platinum oxide catalyst. Ability of (III) and (V) to form o-aminophenolglucuronide was examined with the transferase in microsomes of a guinea pig liver ane only (III) was found to be active. This fact indicated that natural UDPGA takes the same configuration as (III).
