α-Adrenoreceptor Reagents. 2. Effects of Modification of the 1,4-Benzodioxan Ring System on α-Adrenoreceptor Activity

Article abstract of DOI:10.1021/jm00371a003

Modification of the 1,4-benzodioxan ring present in RX 781094 (1) has not previously been considered.This paper describes a number of analogues of this ring system, including compounds in which one of the oxygen atoms has been replaced by a methylene group and also those in which the ring size has been changed to give, for example, furan and thiophene derivatives.The dihydroxybenzofuranylimidazoline compound 7 is the only analogue possesing presynaptic antagonist potency and selectivity comparable to that of 1.In view of this result, a number of derivatives was prepared to determine the structure-activity relationships within this series.Many derivatives, as well as the parent compound 7, were found to possess presynaptic α₂-adrenoreceptor antagonist and postsynaptic α₁-adrenoreceptor partial agonist properties.Two of the selective presynaptic antagonists,13 and 14, possess greater potency and selectivity than that possessed by 1.The 5-chloro derivative 25 is twice as potent as 1 after oral administration but only about half as potent when given intravenously.