tokens: We compared the potential beta - receptor blocker , B 24 / 76 i . e . 1 - ( 2 , 4 - dichlorophenoxy ) - 3 [ 2 - 3 , 4 - dimethoxyphenyl ) ethanolamino ] - prop an - 2 - ol , which is characterized by beta 1 - adrenoceptor blocking and beta 2 - adrenoceptor stimulating properties with propranolol .