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Sir: In the course of a screening program for new antibiotics, we isolated newantibiotics, epoxyquinomicins A (1) and B (2) from the culture broth of Amycolatopsis sp. MK299-95F4, which was isolated from a soil sample collected at Sendai city, Miyagi Prefecture, Japan. In this paper we report the production, isolation, physico-chemical properties, biological properties and structures of 1 and 2 (Fig. 1). A slant culture of the epoxyquinomicins-producing organism was inoculated into a 500 ml Erlenmeyer flask containing 1 10 ml ofa seed medium consisting ofglycerol 0.5%, sucrose 2%, soybeanmeal 1%, dry yeast 1%, corn steep liquor 0.5% and CoCl2 0.001% (adjusted to pH 7.0 before sterilization). The inoculated mediumwas incubated at 30°C for 5 days on a rotary shaker. Two ml of the seed culture was transferred to each 500ml Erlenmeyer flask containing 110ml of a producing medium. The producing mediumwas composed of glycerol 2.0%, dextrin 2.0%, Bacto-Soytone (Difco) 1.0%, yeast extract 0.3%, (NH4)2SO4 0.2% and CaCO3 0.2% (adjusted to pH 7.4 before sterilization). The fermentation was carried out at 27°C for 4 days on a rotary shaker. The culture broth was filtrated and the filtrate (2.55liters) was extracted with «-BuOAc at pH 2. The organic layer was concentrated and dried under reduced pressure. The crude material was dissolved in MeOH (50 ml) and the solution was washed twice with rc-hexane (50ml), followed by concentrating under reduced pressure to dryness. The dried residue was distributed in a mixture of CHC13-MeOH-H2O (100ml, 50: 10:40, v/v). Then the lower layer was concentrated in vacuo to yield a brown oil (0.515g). The oily material was chromatographed on a silica gel column (Merck,

Epoxyquinomicins A and B, New Antibiotics from Amycolatopsis.