ABSTRACT: A total of 24 novel 2,5-diaryl-1,3,4-oxadiazoline analogs of combretastatin A-4 (CA-4, 1) were designed, synthesized, and evaluated for biological activities. The compounds represent two structural classes; the Type I class has three methoxy groups on the A ring and the Type II class has a single methoxy group on the A ring. Biological evaluations demonstrate that multiple structural features control the biological potency. Four of the compounds, 2-(3'-bromophenyl)-5-(3'',4'',5''-trimethoxyphenyl)-2-acetyl-2,3-dihydro-1,3,4-oxadiazoline (9l), 2-(2',5'-dimethoxyphenyl)-5-(3''-methoxyphenyl)-2-acetyl-2,3-dihydro-1,3,4-oxadiazoline (10h), 2-(3',4',5'-trimethoxyphenyl)-5-(3''-methoxyphenyl)-2-acetyl-2,3-dihydro-1,3,4-oxadiazoline (10i), and 2-(3',5'-dimethoxyphenyl)-5-(3''-methoxyphenyl)-2-ace
