The Synthesis of Novel GABA Uptake Inhibitors. Part 2. Synthesis of 5-Hydroxytiagabine, a Human Metabolite of the GABA Reuptake Inhibitor Tiagabine

Article abstract of DOI:10.1016/S0040-4020(01)85345-X

(R)-1-(4-(2,5-Dihydro-3-methyl-5-oxothien-2-ylidene)-4-(3-methyl-2-thienyl)butyl)-3-piperidinecarboxylic acid (5-hydroxytiagabine) 13, has been prepared in 8 steps from 2-bromo-3-methylthiophene 3.Key steps are Grignard reactions, displacement of heteroaromatic chlorine with methoxy, and simultaneously demethylation and opening of a hydroxymethylcyclopropane with bromotrimethylsilane.An alternative approach involving acylation of 2-lithio-3-methylthiophene 17a was found less satisfying.A metalloporphyrin assisted hydroxylation of tiagabine 1 also yielded the target metabolite.The structure of 5-hydroxytiagabine was confirmed by NMR-data including COSY, ROESY, HMQC and HMBC experiments.