P-antagonistic activities

Figure 2.20 The general structure 72, with different residues X, describes the prototype of a (3-adrenergic antagonist. Cyclization of the side chain produced the antidepressant viloxazine 73, whereas the N-n-propyl analog propafenone 74 turned out to be a class Ic antiarrhythmic with only weak P-antagonistic activity. An attempt to cyclize P-blockers to structures of the prototype 75 finally produced levocromakalim 76 as expected, it had antihypertensive activity but its mode of action is different instead of being a P-blocker, it is a potassium channel opener.

Figure 2.2. Propranolol and two of its major metabolites. The hydroxylated derivative still has p-antagonistic activity. The other compound is inactive.

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