An actinomycete strain No. Q996-17 produced a novel compound, epoxomicin, which exhibited in vivo antitumor activity against B16melanoma. Structural studies indicated that it is a newmember of the epoxy-jS-aminoketonegroup, and is closely related to eponemycin.In our continuous search for antitumor agents showing specific activity against B16 murine melanoma, an unidentified actinomycete strain No. Q996-17 was found to produce a new compound epoxomicin. It wasextracted by rc-butanol from the fermentation broth and purified by various chromatographies. Structural studies revealed that epoxomicin has an epoxy-^-aminoketone moiety in the structure and is a newmemberof the eponemycin^group. Epoxomicin exhibited strong in vitro cytotoxicities against various tumor cell lines, whereas it did not exhibit anti-bacterial and anti-fungal activities. It showed strong in vivo inhibitory activity against B16 melanoma but moderate activity against P388 mouse leukemia.

Streptomyces amphibiosporus R310-104 (ATCC53964) produced a novel antibiotic lactimidomycin which showed inhibitory activity against fungi and prolonged the survival time of mice transplanted with experimental tumors. Structural studies clarified that lactimidomycin is a new glutarimide antibiotic having a unique unsaturated 12-memberedlactone ring.In the course of screening for new antibiotics effective against experimental tumors, we have isolated a novel antibiotic designated lactimidomycin from the culture broth of Streptomyces amphibiosporus R310-104 collected in Akita city1'2*. The antibiotic exhibited strong cytotoxicity against various tumor cells and inhibitory activity against fungi but no antibacterial activity. It demonstrated prolongation of life span in mice bearing P388 leukemia and B l 6 melanoma. The structure oflactimidomycin was determined by spectroscopic analyses and 13C-enriched biosynthetic studies to be a novel glutarimide group antibiotic having a unique 12-memberedlactone ring as a side chain.In this paper, we describe the production, isolation, physico-chemical properties, structure determination and biological activity of lactimidomycin. Antibiotic Production A loopful mature slant culture of S. amphibiosporus R3 10-104 was inoculated into 100 ml of vegetative mediumconsisting of soluble starch (Nichiden Kagaku) 2%, Pharmamedia(Traders Protein) 1%, ZnSO4-7H2O0.003% and CaCO3 0.4% in a 500-ml Erlenmeyer flask (pH 7.0 before sterilization).The flask was incubated at 32°C for 7 days on a rotary shaker (200rpm) and 5 ml of vegetative inoculum was added to 100ml of sterile production medium containing Protein-S (Ajinomoto Co.) 3%, glucose 3%, Pharmamedia 0.5%, yeast extract (Oriental Yeast Co.) 0.1% and CaCO3 0.3%, pH 7.0 in a 500-ml Erlenmeyer flask. The flask was incubated at 28°C on a rotary shaker (200rpm). Antibiotic production was monitored by the in vitro cytotoxicity against B16 melanomacells and it reached maximumafter 4 days incubation. Isolation and PurificationThe fermentation broth (18 liters, pH 7.4) was stirred with 1-butanol for one hour. The solvent layer was separated from the aqueous layer and mycelial cake by use ofa Sharpies type centrifuge and concentrated under reduced pressure. The residue (30 g) was suspended in water (1 liter) and extracted three times with Lactimidomycin was originally called as BU-4146T or BMY-28886.

Based on the structure-activity relationship data of BMY-28864 and related pradimicin derivatives, the calcium salt-forming ability and the D-mannopyranoside-speciflc visible absorption maximumshift of BMY-28864 were analysed in the ternary complex formation of BMY-28864 with D-mannopyranoside and calcium. The free C-18 carboxyl group of BMY-28864 was proved to be the sole site for binding to calcium, while no hydroxyl groups of the aglycone were involved in calcium salt formation. The stereospecific D-mannopyranoside-recognizing ability of BMY-28864 was completely abolished by removal of the C-5 disaccharide moiety, and, more particularly, of the C-5 thomosaminemoiety. Close relationship of these findings with the antifungal action was also supported by the in vitro antifungal assay and the potassium leakage induction test.In previous papers1~4), the in vitro antifungal activities of pradimicin and benanomicin derivatives on yeasts were shown to be specifically expressed only in the presence of calcium. Using BMY-28864, a water-soluble pradimicin derivative, specific binding of the pradimicin to yeast cells was proved to depend on the ternary complex formation of BMY-28864with mannan and calcium at a molar ratio of 2 :4 : 15). This highly stereospecific binding of BMY-28864 to the mannose unit (more generally, the specific sugar-recognizing ability of the pradimicin and benanomicin family of antibiotics) is biochemically worth studying, as it is currently unexplicable by the widely accepted concepts of receptor-ligand binding in the light of lectin and carbohydrate sciences. Lectins have been considered to recognize specific sugars based on the intrinsic properties of their peptide components, whereas the pradimicin and benanomicin family of compounds are not peptides. Under these circumstances, it is crucially important and essential to more precisely elucidate the mechanismof ternary complexformation of pradimicins with specific sugars and calcium in critical comparison with lectins. This type of knowledge is not only biochemically useful for receptology, but also clinically important from the viewpoint of selective toxicity of final pradimicin drugs in hosts, as sugars are essential cellular components of host animals to be treated with pradimicin, and assumed to exist ubiquitously at significant concentrations in a variety of forms throughout therapy.In this paper, the structure-activity relationship of BMY-28864 and related pradimicin derivatives is analyzed for identification of the moieties of BMY-28864responsible for binding to D-mannopyranoside and calcium and for induction of the visible absorption maximumshift. In brief, only the free C-18 carboxyl group of BMY-28864serves to bind to calcium as salt, while the C-5 disaccharide moiety is essential for specific recognition of and binding to D-mannopyranoside.

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Quinaldopeptin, a new type of quinomycin antibiotic, was isolated from the culture of Streptoverticillium album strain Q132-6. The antibiotic exhibited strong in vitro antimicrobial and cytotoxic activity and significantly prolonged the survival time of mice inoculated with a murine tumor. Quinaldopeptin is a symmetric cyclic peptide linked only by peptide bonds and differs from known antibiotics of the quinomycin family by the lack of ester linkage.In our search for microbial metabolites with antitumor activity, a novel antibiotic, quinaldopeptin has been isolated from the cultured broth of Streptoverticillium album strain Q132-6 which was isolated from a soil sample collected in AndhraPradesh, India. The antibiotic was recovered from the fermentation broth by solvent extraction and purified by chromatography. Structural studies combining spectral analysis and chemical degradation disclosed that quinaldopeptin is a symmetric cyclic peptide comprised of 2 mol each of 3-hydroxyquinaldic acid, glycine, sarcosine and a,/?-diaminobutyric acid and 4mol of pipecolic acid. Although quinaldopeptin should be classified in the quinomycin group of antibiotics, it distinctly differs from the known compounds by the lack of an ester linkage. Quinaldopeptin is highly active against Gram-positive bacteria and anaerobes and strongly cytotoxic against cultured B16melanomacells. It prolonged the survival time of mice transplanted with P388 leukemia. This paper describes the isolation, properties, structural determination and biological activities of quinaldopeptin.