Synthesis of Analogs of GABA .15. Preparation and Resolution of Some Potent Cyclopentene and Cyclopentane Derivatives

A series of cyclopentene and cyclopentane analogues of GABA has been prepared utilizing a thermal cis -trans isomerization of the phthalimido β,γ -unsaturated acid (10) as the key step to obtain trans-4- aminocyclopent-2-ene-1-carboxylic acid (7). Resolution of some of the potent GABA analogues, in particular (+)-(4S)- and (-)-(4R)-4- aminocyclopent-1-ene-1-carboxylic acid (5), has been achieved by crystallization of isopropylideneribonolactone esters or pantolactone esters of the phthalimido -protected intermediates.