“…4 For such routes, a high degree of control of the relative stereochemistry about the pyrrolidine positions 3 and 4 is required in order to produce the normal cis-kainic acid stereochemistry or the isomeric trans-allokainic acid stereochemistry. Use of Lewis acid catalysts to promote the ene cyclisation under milder conditions generally affords mainly the cyclic 3,4-trans isomers, 5 although, using the pyrrolidone precursor 5, Xia and Ganem showed that magnesium perchlorate catalysed the ene cyclisation to give mainly the cis-product 6. 6 Ene-routes to kainic acid and its congeners have been described by Oppolzer 7 , Kennewell et al 2 , Kirihata et al, 8 and Ogasawara and co-workers.…”