Purification Methods
Purify the acid by re-precipitation from an alkaline solution by HCl, filter it off, and recrystallise it from water several times, rejecting the first crop. It forms leaflets from EtOH and Me2CO and H2O and is insoluble in CHCl3. Its solubility in H2O is 0.8% at 25o and 10% at 100o, 50% in EtOH and 5% in ethylene glycol. The (±)-acid has m 202-203o. The (+)-1-methyl ester has m 86o (from pet ether) [] 20 +45o (c 4, EtOH), and the (+)-3-methyl ester has m 77o (from pet ether) []17.5 +53.9o (c 3, EtOH). [Rupe & Thommen Helv Chim Acta 30 933