OH 1 (norepinephrine) 2 (methoxamine) 3 (phenylephrine) about equal potency on both pre- and postjunctional a receptors (ECm on al= 1.5 XM). Other agents, such as methoxamine (2) or phenylephrine (3), are more selective for the postjunctional al receptor. 2 In a previous paper in this series2 we described the synthesis and al-adrenergic potency of a series of structurally diverse compounds related to the a,-agonist methoxamine. From among these ...