Bis- and tris-dihydroxyaryl compounds and their methylenedioxy analogs and pharmaceutically acceptable esters, their synthesis, pharmaceutical compositions containing them, and their use in the treatment of amyloid diseases, especially A.beta. amyloidosis, such as observed in Alzheimer's disease, IAPP amyloidosis, such as observed in type 2 diabetes, and synucleinopathies, such as observed in Parkinson's disease, and the manufacture of medicaments for such treatment.