The title compd. is, monoclinic, space group P21, with a 6.619(1), b 7.339(1), c 11.284(2) .ANG., and b 103.63(1) Deg; d.(calcd.) = 1.043 for Z = 2. Final R = 0.082 for 838 reflections. At. coordinates are given. Although disorder occurs in the 6-membered lactam ring and the iso-Pr group, the antiperiplanar conformation of the vinyl group relative to the amide system in the title compd. is established. The crystal structure is stabilized by intermol. H bonds between the vinylic b-H atom and the carbonyl O atom of the next mol., with a distance of 2.5 .ANG..