The enaminone (4), prepared from (2S)-pyroglutamic acid, has been reac
ted with Grignard reagents to afford a variety of (E)-alkylidene deriv
atives (8). Three of these have been converted to the 4-alkylideneglut
amic acids, (1), (2) and (3), which are identical to known natural pro
ducts, (2) and (3) being the E-isomers.