Dehydro-oligopeptide cpds. - useful for treatment of tumours

Dehydro-oligopeptides of formula (I) and their salts are new. In (I) R1 is opt. substd. alkyl, alkenyl, aryl, hetero-R1CONH-C-CO-(NH-C-CO)m-(NR6-CR7R8-CO)nR9 (I) cyclyl, aralkyl or aralkenyl, or CONH; R2 is H or lower alkyl, and R3 is Et, cycloalkyl or opt. substd. heterocyclyl, aryl, aralkenyl or aralkyl, or CR2R3 is 5-6C cycloalkylidene or cycloalkenylidene; R6 is H or alkyl, R7 is substd. benzyl, CH2OH, C2H4SMe, C2H4CONH2 or C2H4COOH and R8 is H, or R6+R7 is 3-4C alkylene, or R7 +R8 is 4-5C alkylene; R9 is OH, NH2, an opt. substd. alkylamino, arylamino, aralkylamino, aralkoxy, alkoxy, alkylthio or hydrazino gps., or an opt. substd. 5- or 6-membered N-contg. heterocycle opt. contg. other heteroatoms m and n are 0 or 1 but cannot both be 0. Cpds. (I) can be used to resolve tumours and other tissues interfering with normal biological functions, often without affecting the surrounding healthy tissue. They have low acute toxicity (LD50 is approx. 300 mg/kg. i.v., rat) and are effective at doses of 1-100 (pref. 2-40) mg/kg. A typical cpd. is N-acetyldehydrophenylalanyl-D-proline. In an example, this is prepd. from 2-methyl-4-benzylidene-5(4H)-oxazolone and D-proline.