Epipodophyllotoxin /3-D-glucopyranoside (XIII), 4'-demethylepipodophyllotoxin /3-D-glucopyranoside (XV), and 4'-demethylepipodophyllotoxin /3-o-galactopyranoside (XVI) react with aldehydes and ketones in the presence of acid catalysts to yield the corresponding cyclic acetals and ketals, resp. A number of 4 '-demethylepipodophyllotoxin /3-D-glucopyranoside derivatives exhibit a high cytostatic activity in vitro (P-815 mastocytoma cell culture) and give significant survival time increases in the mouse leukemia L-1210.

Tetronomycin, C34Hsu08, isolated from a strain of Streptomyces sp. nov. represents a novel

Cyclapeptide antibiotics from Aspergillus species. Structure of echinocandins C and D SummuryThe echinocandins B, C and D are antifungal antibiotics produced by a strain of Aspergillus rugulosus. All three metabolites are closely related representing cyclic oligopeptides composed of six amino acids and a linolic acid residue in an amide linkage. The complete structure of echinocandin B (1) has recently been established by X-ray analysis. Structural assignments to the new minor metabolites C and D have now been made by hydrolytic and oxidative cleavage reactions, formation of N-acyl-u-aminoethers as well as by chemical correlations and extensive NMR. examinations. Echinocandin C (2), CS2H8 15, contains 3-hydroxyhomotyrosine in the place of 3,4-dihydroxyhomotyrosiiie present in 1. Ikhinocandin D (3), C,,H,IN,O 13, differs in two amino acids: 3,4-dihydroxyhomotyrosine and 4,5-dihydroxyornithine, unusual units of 1 being replaced by 3-hydroxyhomotyrosine and ornithine.

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NoboritomycinsA and B, two new polycyclic ionophoric polyethers were isolated from a strain of Streptomyces noboritoensis. The crystal structure and absolute configuration of noboritomycin A were established by X-ray analysis of its silver salt C43H63O1,Ag. Noboritomycin A is the first metabolic polyether possessing two carboxylic acid functions on the carbon backbone (C-31), namely a free acid and an additional carboxylic acid ethylestergroup. An unusual spiroketal system as well as a salicylic acid chromophore represent further remarkable elements. Noboritomycin A shows in this respect a structural relationship to salinomycin and lasalocid respectively. Comparison of physico-chemical data, in particular the interpretation of the 1H-and 13C-NMR spectra, revealed that noboritomycins A and B are structurally closely related, noboritomycin B carrying an ethyl substituent on the aromatic ring in the place of a methyl group present in noboritomycin A. Both metabolites exhibit activity against Gram-positive bacteria and against Eimeria tenella (chicken coccidiosis).In the course of our screening for new antibiotics from soil actinomycetes we isolated a strain of Streptomyces noboritoensis (NRRL 8123) which produced two metabolites effective against Grampositive bacteria. The active compounds designated as noboritomycins A and B were characterized as carboxylic acid ionophores and represent new members of the polyether antibiotic group.') This report deals with the taxonomy of the producing strain, as well as fermentation, isolation, structure and biological activities of noboritomycins A and B.