Expression of the aranciamycin biosynthetic gene cluster in Streptomyces diastatochromogenes Tü6028 resulted in production of four novel compounds, aranciamycins E, F, G, and H with different decorations in the tetracyclic backbone. Two derivatives contain a D-amicetose moiety at C7 (aranciamycins F and G), two are hydroxylated at position C1 (aranciamycins E and G), and one is hydroxylated at C13 (aranciamycin F). Analysis of the biological activities of the aranciamycins against two human tumor cell lines--MCF-7 and MATU--shows surprising impact of the hydroxyl group at position C1 on activity. As aranciamycins E and G were the most active derivatives, hydroxylation of the C1 appears to coincide with increased antitumor activity of aranciamycins.