Methylephedrine → (-)-Galantamine

Participants

Reaction Steps

Lithium aluminium hydride (1M in ether, 1.2 ml, 1.20 mmol) was placed in a two necked round bottom flask fitted with a reflux condenser and nitrogen inlet. (-)-N-methylephedrine (0.23 g, 1.26 mmol) in ether (1 ml) was added dropwise and the solution was heated at reflux for 1 hour then cooled to room temperature. N-Ethyl-2-amino-pyridine (0.31 g, 2.52 mmol) in ether (1 ml) was added and the bright yellow solution was heated under reflux for a further 1 hour. The solution was cooled to -78° C. and solid racemic narwedine (0.10 g, 0.35 mmol) was added. The suspension was stirred for 3 hours at -78° C. and then allowed to warm to room temperature over 1 hour. The reaction was quenched with hydrochloric acid (3M, 2 ml). The aqueous layer was removed and basified with KOH to pH 14. The remaining mixture was extracted with dichloromethane (3×10 ml) and the combined organic layers were washed with water (5 ml) and brine (5 ml) and dried over magnesium sulphate. Filtration and evaporation gave an orange oil which was flash chromatographed on silica in dichloromethane-methanol 10:1 to yield (-)-galanthamine (50% e.e.) as a white solid (0.036 g, 36%), pure by NMR.

Provenance & Evidence