TACA(反式-4-氨基巴豆酸)是GABAA和GABAC受体的有效激动剂,其半数有效浓度(KD)为0.6μM。此外,TACA还是GABA摄取的抑制剂以及GABA-T的底物。在MPG神经元中,TACA能够引发晚期双相反应。
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.
A series of 4-alkyl-4-aminobut-2-enoic acids (2)-(5) has been prepared as conformationally restricted analogues of GABA. The synthetic route which involved allylic bromination followed by displacement with ammonia also gave vinyl glycine analogues (7)-(9) as readily purified by-products of the reaction. The low biological activity in vitro against GABA uptake, binding and enzyme systems of (E)-2-aminocyclohexylideneacetic acid (4) and (E)-2-aminocyclopentylideneacetic acid (5) has been interpreted in terms of steric hindrance by the ring-forming methylene groups at the particularactive sites concerned.