Polyene oxazoles of the following formula ##STR00001## wherein R.sub.3 is selected from H and methyl, are disclosed. Such compounds, and pharmaceutically acceptable salts thereof, may be used in the inhibition of tumor cell growth. The polyene oxazoles and their pharmaceutically acceptable salts may be formulated as pharmaceutical compositions with pharmaceutically acceptable carriers for use in the inhibition of tumor cells. The polyene oxazoles may be obtained from strains of Streptomyces sparsogenes, such as strain 022 having deposit number IDAC 270504-04.