Synthesis, X-ray crystallographic analysis, and antitumor activity of 1-acyl-3,6-disubstituted phenyl-1,4-dihydro-1,2,4,5-tetrazines

Eleven compounds of 1-acyl-3,6-disubstituted phenyl-1,4-dihydro-1,2,4,5-tetrazines were prepared from 3,6-disubstituted phenyl-1,2-dihydro-1,2,4,5-tetrazines and anhydrides or acyl chlorines, and their structures were confirmed by single-crystal X-ray diffraction and the semi-empirical calculation of PM3 method. This reaction yields the 1,4-dihydro derivatives rather than the 1,2-dihydro derivatives. The central six-membered ring of these compounds has an obvious boat conformation and therefore is not homoaromatic. Their antitumor activities were evaluated in vitro by the SRB method for A-549 cell and the MTT method for P-388 cells. The results show that there is one compound which is highly effective against A-549 cells and two compounds which are highly effective against P-388 cells. Thus, this compound possesses potential antitumor activities and is worth researching further.