
%0 Journal Article
%A Allan, RD 
%A Johnston, GAR 
%A Twitchin, B 
%T Synthesis of analogues of GABA. V. <I>trans</I> and <I>cis</I> Isomers of some 4-amino-3-halogenobut-2-enoic acids
%J Australian Journal of Chemistry
%D 1980/05/01
%V 33
%N 5
%P 1115-1122
%K 
%R https://doi.org/10.1071/CH9801115
%U https://www.publish.csiro.au/paper/CH9801115 
%X Both trans and cis isomers of 4-amino-3-halogenobut-2-enoic acid have been prepared as potential irreversible inhibitors of the enzyme GABA- transaminase. trans-Addition of HX to 4-chlorobut-2-ynoic acid and subsequent amination gave the trans isomers (2; X = Cl, Br, I), while the key step in the synthesis of the cis isomers (3; X = Cl, Br) was the isomerization to cis-4-bromo-3-halogenobut-2-enoic acids during allylic bromination. The stereochemical assignments are supported by 1H and 13C n.m.r. spectral data. A convenient preparation of cis-4- aminobut-2-enoic acid by reduction of the bromo derivative is described, as well as the synthesis of 4-phthalimidobut-2-ynoic acid which is suitable for preparing radiolabelled GABA of high specific activity. 
