Dissolve it in cold 2.5N NaOH, extract with CH2Cl2, and acidify with 5% HCl. Collect the white precipitate and recrystallise it from aqueous EtOH and dry it in a vacuum [Akimoto & Yamada Tetrahedron 27 5999 1971]. It is optically stable in dioxane-water (100o/24hours). Racemisation: 72% in 1.2N HCl at 100o/24hours and 68% in 0.67M KOH in BuOH at 118o/23hours [Kyba et al. J Am Chem Soc 95 2693 1973]. It has also been crystallised from *C6H6 (solubility is 1%) using Norite or aqueous EtOH after chromatography through silica gel, eluting with Me2CO/*C6H6. [Kyba et al. J Org Chem 42 4173 1977; see also Brussee & Jansen Tetrahedron Lett 24 3261 1983, Akimoto & Yamada Tetrahedron 27 5999 1971, Beilstein 6 IV 7020.]
