STRUCTURE-ACTIVITY RELATIONSHIP OF BETA ADRENORECEPTOR BLOCKING AGENTS

The β-adrenoreceptor blocking activity of the nitro and the methyl substituted phenylethanolamine and phenoxypropanolamine series of agents was determined in the isolated turtle heart preparation. The pA2 values for both INPEA and para-methylisoproterenol were found to be 6.9. In the n-isopropylphenoxypropanol derivatives, substitution with a methyl group in the meta position of the phenolic nucleus yielded the most active compound (Kö 592) which has a pA2 value of 8.3. The adrenoreceptor blocking activity was greatly reduced when the methyl substitution was made in either para or ortho positions in this series. In the nitro substituted compounds, however, the blocking activity is markedly reduced in the phenoxypropanolamine series of agents as compared to the phenylethanolamine derivative (INPEA). The structural requirements for the two groups of β-adrenoreceptor blocking agents are different. © 1969.