反应详情

A mixture of d,l-3-[(3,5-dimethoxy-N-ethoxycarbonyl)anilino]butyric acid (136.6 g., 0.44 mole) and l-ephedrine (72.5 g., 0.44 mole) is dissolved in methylene chloride (500 ml.). The methylene chloride is then removed in vacuo to yield the 1-ephedrine salt of d,l-3-[(3,5-dimethoxy-N-ethoxycarbonyl)anilino]butyric acid as an oil, [α]D25 =-20.0 (c=1.0, CHCl3). Addition of ether (1500 ml.) causes crystallization of a white solid which is separated by filtration and dried (102 g.), m.p. 114°-116° C. Recrystallization from ethyl acetate/hexane (1:1) affords 71.1 g. (34%) of the l-ephedrine salt of l-3-[(3,5-dimethoxy-N-ethoxycarbonyl)anilino]butyric acid; m.p. 126°-127° C.

1. customThe methylene chloride is then removed in vacuo