Purify it through an Al2O3 column and eluting with pet ether (40-60o) then Et2O and recrystallising from pet ether or EtOH. The acetate crystallises from Ac2O or pet ether and has m 242-143o and [] D +82.8o (c 0.81, CHCl3) [Crow & Michael Aust J Chem 8 133 1955, Barton et al. J Chem Soc (C) 1031 1968, Beilstein 6 III 1894, 6 IV 4195.]