SYNTHESIS AND FUNGITOXICITY OF NEW PEPTIDYL 1,3,4-OXADIAZOLO[3,2-A]PYRIMIDIN-5-ONES

Michael addition of nitrogen nucleophiles 2-amino-5-aryl-1,3,4-oxadiaz oles IIa,b to 4-arylidene-5-oxazolones Ia,b followed by ring transform ation of the resultant Michael adducts IIIa-d yielded dihydro-5H-1,3,4 -oxadiazolo[3,2-a]pyrimidin-5-ones IVa-d in a one-pot procedure. The c ompounds IVa-d on deacetylation furnished their g-amino analogues Va-d , which were converted into their 6-peptidyl (Gly-Gly and Gly-L-Phe) a mino derivatives VIIa-h. The compounds III-V and VII were evaluated in vitro for their fungitoxicities against Aspergillus niger and Fusariu m oxysporum. Some of the compounds displayed activities comparable wit h that of the commercial fungicide Dithane M-45. Structure-activity re lationships for the screened compounds are discussed.