Synthesis of simple analogues of methyllycaconitine—an efficient method for the preparation of the N-substituted anthranilate pharmacophore

The synthesis of several A and AE ring analogues of the alkaloid methyllycaconitine is reported. The key 2-(2″-methylsuccinimido)benzoate ester pharmacophore is introduced using an efficient two step procedure. Esterification of the alcohol precursors with N-(trifluoroacetyl)anthranilic acid under Steglich conditions followed by sodium borohydride mediated cleavage of the trifluoroacetyl group affords the anthranilate esters. Subsequent fusion with methylsuccinic anhydride affords the N-substituted anthranilate derivatives containing the key pharmacophore present in a range of commonly occurring Delphinium and Aconitum alkaloids.