Purification Methods
Recrystallise -erythroidine from pentane. It is best prepared freshly from the more stable hydrochloride. The hydrochloride (1.3g) in H2O (20mL) is basified with NaHCO3 to pH ~8 and extracted with *C6H6 (6 x 10mL). The combined extracts are evaporated to a small volume and refrigerated. The free base separates as white hygroscopic crystals m 52-55o, which are recrystallised from pentane. Although stable in solution, the crystals turn brown on exposure to air.
-Erythroidine hydrochloride is best purified by dissolving 10g in H2O (100mL), adjusting the pH to 8 with aqueous NaHCO3, extracting with *C6H6 (4 x 20mL), evaporating to 20mL, passing through activated Al2O3 and eluting with *C6H6. The eluate is evaporated to a small volume and the crystals are collected, dissolved in EtOH and dry HCl gas passed through to give the pure hydrochloride. When recrystallised from EtOH, it has m 226-228o(dec), and [ ] D 32 +118o (c 0.5, H2O). It has max 224nm ( 35,500); compare with -erythroidine hydrochloride below. [Boelkeleide & Grundon J Am Chem Soc 75 2563 1953, Boekeleide & Morrison J Am Chem Soc 80 3905 1958, abs config: Hill & Shearer J Org Chem 2 7 3342 1955, Beilstein 27 III/IV 3569.]
