Polyene compounds

A compound represented by the formula ##STR23## wherein one of R.sub.1 or R.sub.2 is ##STR24## and the other of R.sub.1 or R.sub.2 and R.sub.3 and R.sub.4 are hydrogen, lower alkoxy-lower alkyl, hydroxy methyl, halogen, lower alkyl, lower alkoxy, amino, carboxyl, mono(lower alkyl)amino, lower alkyl thio, di(lower alkyl)amino, mono(lower alkyl)amino lower alkyl, di(lower alkyl)amino lower alkyl, hydroxy, lower alkenyl, lower alkenoxy, lower alkanoyl, lower alkanoyloxy, nitro, lower alkoxycarbonyl, lower alkanoylamido or a nitrogen containing heterocycle, selected from the group consisting of piperidino, morpholino, thiomorpholino and pyrrolidino and R.sub.5 is formyl, hydroxymethyl, alkoxymethyl, alkanoyloxymethyl, alkoxycarbonyl, aroyloxymethyl or an N-heterocyclylcarbonyl selected from the group consisting of piperidino, morpholino, thiomorpholino and pyrrolidino;

• with the proviso that when R.sub.5 is alkoxycarbonyl, at least one of R.sub.1, R.sub.2, R.sub.3 and R.sub.4 is lower alkoxy-lower alkyl, hydroxy methyl, halogen, lower alkoxy, amino, carboxyl, mono(lower alkyl)amino, lower alkyl thio, di(lower alkyl)amino, mono(lower alkyl)amino lower alkyl, di(lower alkyl)amino lower alkyl, hydroxy, lower alkenyl, lower alkenoxy, lower alkanoyl, lower alkanoyloxy, lower alkoxycarbonyl, lower alkanoylamido or a nitrogen containing heterocycle, selected from the group consisting of piperidino, morpholino, thiomorpholino and pyrrolidino.