[1, 1, 1, 2, 2-D5] E-3, 4-Di-(4-hydroxyphenyl)-hex-3-ene has been synthesized from 1, 1-di-(4-benzyloxyphenyl)-butyraldehyde. The preparation of this aldehyde is described. Its reaction with pentadeuterated ethyl magnesium bromide yields [1,1,1,2,2-D5] 4,4-di-(4-benzyloxyphenyl)-hexan-3-ol, which is debenzylated by catalytical hydrogenation. Upon heating of the resulting [1,1,1,2,2-D5] 4,4-di-(4-h