An increasing number of biologically active compounds contain the 2,4-disubstituted oxazole ring including the streptogramin A antibiotics,1 View all references the potent antitumor phorboxazoles,2 View all references the highly cytotoxic disorazoles,[3]8. Jansen , R. , Irschik , H. , Reichenbach , H. , Wray , V. and Hofle , G. 1994. Liebigs Ann. Chem., : 759–773. ... View all references the secondary metabolite ajudazols,[4]9. Jansen , R. , Kunze , B. , ...