Opticalisomers of TZC-1370 (1) were prepared from (R)- and (S)-1-(2-chlorophenoxy)-2,3-epoxypropane. When given intravenously to anesthetized rats, the (S)-isomer was about 40 times more potent in terms of beta-blocking activity than the (R)-isomer, while their hypotensive activities were equipotent with that of the racemic compound, TZC-1370.