Abstract: This invention relates to: (a) compounds of formula I (with R1 to R5 and A as defined herein) and pharmaceutically acceptable salts or solvates thereof that are useful as dopamine-?-hydroxylase inhibitors; (b) pharmaceutical compositions comprising such compounds, salts or solvates; (c) the use of such compounds, salts or solvates in therapy; (d) therapeutic methods of treatment using such compounds, salts or solvates; and (e) processes and intermediates useful for the synthesis of such compounds.