Synthesis of a new triprotonated ligand and selective o-demethylation of methyl aryl ether by boron tribromide

Selective O-demethylation of the ortho methyl catecholate of N,N′,N″-tris-(2,3-dimethoxybenzoyl)-1,1,1-tris-(L-methioninemehyl)-ethane (7) has been accomplished by boron tribromide. The intramolecular nucleophilic attack of divalent sulphur on methyl enhance this cleavage, favours this selctivity and consequently afford the triprotonated ligand N,N′,N″-tris-(2-hydroxy-3-methoxybenzoyl)-1,1,1-tris-(L-methioninemethyl)-ethane (8) in a good yield.