Purification is as for isoxanthopterin (see “Heterocyclic Compounds”, Chapter 4). It is crystallised by acidifying a hot ammoniacal solution with formic acid, and collecting the crystals by centrifugation followed by washing with EtOH, ether and drying at 100o in vacuo. Its RF values on paper chromatography are 0.15 (n-PrOH, 1% aqueous NH3, 2:1), 0.36 (n-BuOH/AcOH/H2O, 4:1:1) and 0.47 (3% aqueous NH3). [Inoue & Perrin J Chem Soc 260 1962, Inoue Tetrahedron 20 243 1964, see also Blakley Biochemistry of Folic Acid and Related Pteridines North Holland Publ Co, Amsterdam 1969, Beilstein 26 II 313, 26 III/IV 4000.]
