Variations of acidic functions at position 2 and substituents at positions 4, 5 and 6 of the indole moiety and their effect on NMDA-glycine site affinity.

The synthetic procedures to obtain indole derivatives with different acidic functions at position 2 of the indole are reported. The synthesised and tested derivatives comprise 5-tetrazolyl, 1,3,4-oxadiazol-5-yl-2-one, and indole-2-carboxylic acid amides with 5-aminotetrazole, methanesulphonamide and trifluoromethanesulphonamide moieties. The binding affinity was evaluated using [3H]MDL 105,519 and pig cortical brain membranes. In general, compounds with acidic functions different from a carboxylic acid moiety are less potent than indole-2-carboxylic acid derivatives. Also, the 4,6-dichloro substitution pattern was compared to 5-tert-butyl derivatives and compounds not substituted in the benzene moiety of the indole, indicating that the affinity increases from 5-tert-butyl over unsubstituted to 4,6-dichloro substituted derivatives.