Seven new related compounds named bispolides A1, A2, A3, B1, B2a, B2b and B3, have been found in a culture of Microbispora sp. A34030, isolated from a Malaysian soil sample. The planar structures were elucidated to be new 20-membered ring macrodiolide antibiotics on the basis of MS and NMR spectroscopic analyses. These antibiotics showed a good anti-MRSA activity in vitro.Keywords bispolide, macrodiolide antibiotic, 20-menbered ring, symmetric cyclic dimmer, Microbispora sp.In our screening program of new microbes and their useful metabolites from the tropical resources in Malaysia, seven new related compounds, bispolides A1, A2, A3, B1, B2a, B2b and B3, have been found in a culture of Microbispora sp. A34030. The strain was isolated from a soil sample collected at a forest station in the Forest Research Institute (FRIM), Selangor, Malaysia and was deposited in a Japanese International depository, the International Patent Organism Depositary (IPOD) of the National Institute of Advanced Industrial Science and Technology, under the deposit number of FERM BP-10505.The liquid seed culture (1 ml) of Microbispora sp. A34030 was inoculated into a 500-ml Erlenmeyer flask containing 100 ml of a culture medium composed of glucose 1.0%, cotton seed meal 1.0%, powdered yeast extract 1.0% and calcium carbonate 0.2% (pH 7.0). Forty flasks (4 liters) were cultured at 28°C for 12 days on a rotary shaker at 225 rpm. The mycelium separated by centrifugation was extracted with 100 ml of methanol (twice) and concentrated to 50 ml. The concentrate was extracted with 150 ml of ethyl acetate and evaporated to dryness, which was applied to a column of silica gel (Merck, Art.1.07734.1000, 21 g). The column was eluted with CHCl 3 (200 ml), CHCl 3 -MeOH (50 : 1, 200 ml), CHCl 3 -MeOH (25 : 1, 156 ml) and CHCl 3 -MeOH (25 : 4, 120 ml) in this order. The active eluate in the 25 : 4 ratio was concentrated to give 243 mg of the crude product which was further purified by HPLC (Agilent, ZORBAX XDB-C18 Prep HT 5 m m, 21.2ϫ150 mm) with CH 3 CN -H 2 O (4 : 1) at 12.5 ml/minutes. Thus, seven highly purified components of bispolides were obtained; B1 (15.6 mg) at Rt 4.8 minutes, A1 (28.8 mg) at 6.9 minutes, B2a (19.8 mg) at 9.7 minutes, B2b (10.8 mg) at 11.2 minutes, A2 (45.8 mg) at 15.5 minutes, B3 (20.6 mg) at 23.6 minutes, and A3 (50.0 mg) at 32.7 minutes. The physicochemical properties are shown in Table 1 Table 2, only 31 and 32 signals were observed in the 13 C NMR of bispolides A1 and A3, respectively, and their
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