(11R)-13-[2-(4-Hydroxy-phen-yl)ethyl-amino]-4,5-ep-oxy-11,13-dihydro-costunolide monohydrate

12-{[2-(4-hydroxyphenyl)ethyl]aminomethyl}-4,8-dimethyl-3,14-dioxatricyclo[9.3.0.0(2,4)]tetradec-7-en-13-one monohydrate), C(23)H(31)NO(4)·H(2)O, was obtained by the reaction of tyramine with parthenolide. The configuration of the new chiral center in the title compound is R, establishing the stereospecificity of the amination reaction. The water molecule is disordered over three positions; the site occupancy factors are 0.45, 0.40 and 0.15.