A novel class of antibiotics was isolated from cultures of Streptomyces coeruleorubidus strain AB1183F-64. The antimicrobial activity of the pacidamycins is selective against Pseudomonasaeruginosa. The various congeners are nucleoside peptides which differ in the terminal amino acid residues. The structures were determined using MS-MSand 2D NMR techniques.

A novel complex of Gram-positive antibiotics has been isolated from the fermentation broth and myceliumof Dactylosporangiumaurantiacum subsp. hamdenensissubsp. nov. The structures of these six compoundswere deduced employing UV,MS, IR, and extensive ID and 2Dhomonuclear and heteronuclear NMR experiments. Each componentcontained a highly unsaturated 18-memberedmacrolide ring. Components differed from one another by minor structural variations in the macrolide ring and by the numberand esterification pattern of glycosidically bound sugars.In the course of screening microorganisms for the production of antibiotics a Dactylosporangium species was discovered which produced a novel complex of 18-membered macrolides. The companion paperx) describes the taxonomy and fermentation of this organism and the biological activity of the individual antibiotics. This paper will describe the isolation of these components and the elucidation of their structures.Isolation of Tiacumicins A, B and C As outlined in Fig. 1, whole broth (20 liters) was adjusted to pH 7 with dilute HC1, then centrifuged and filtered through filter paper to remove the mycelial cake. The filtered broth was extracted three times with ethyl acetate (3 x 10 liters). Ethyl acetate extracts were combined, dried over sodium sulfate, and concentrated under vacuumto an oily residue. The residue was chromatographed on a Sephadex LH-20 column (1 liter) eluted with CH2C12 -MeOH(2 : 1). Active fractions were pooled and subjected to counter-current chromatography of an Ito multilayer coil planet centrifuge employing a CC14-CHC13 -MeOH-H2O(7:3 :7:3) solvent system (lower phase stationary).Three active bands from the coil planet centrifuge were separately chromatographed on Sephadex LH-20 eluted with CH2C12 -MeOH(2 : 1) to yield three pure components; tiacumicins A (10 mg), B (35 mg) and C (24 mg). The mycelial mass was soaked twice in acetone (2 x 1 liter) which was then filtered off and evaporated to an aqueous concentrate. This aqueous suspension was diluted with distilled water to a volume of 2 liters and extracted three times with ethyl acetate (3 x 1 liter). Ethyl acetate extracts were combined, dried over sodium sulfate and concentrated to an oily residue. The residue was triturated twice with hexane (2 x 1 liter) and the hexane layers were discarded leaving an oily residue. Chromatographic processing analogous to that of the broth extract yielded additional tiacumicins B (12mg) and C (8 mg).

A family of novel compounds has been detected and isolated following an assay for the attenuation of multiple drug resistance in tumor cells from the fermentation broth and mycelia of a strain of Aspergillus fischeri which we have designated var. brasiliensis. The structures of three components were determined employing 1-D and 2-D homonuclear and heteronuclear NMRspectroscopy and mass spectrometry. The structure of 5-7V-acetylardeemin was confirmed by single crystal X-ray diffraction.These compounds are most closely structurally related to asperlicin E1}.In the course of screening for compounds which reverse multi-drug resistance to antitumor antibiotics, the ardeemins were isolated from a newstrain of Aspergillus fischeri (designated var. brasiliensis).A companion paper2) describes the taxonomy and fermentation of the producing organism and the biological activities of ardeemin (1) and 5-7V-acetylardeemin (2). This paper will describe the isolation and structures of these novel heterocyclic compounds.Isolation of the Ardeemins Upon completion of the fermentation, 8 liters of acetone was added to 20 liters of whole broth and the mixture was stirred for 3 hours (See Fig. 1). To this was added 16 liters of ethyl acetate and the resultant mixture was stirred for 1 hour at which time the organic layer was removed. Anadditional 16 liters of ethyl acetate was added to the aqueous acetone and the mixture was stirred for 1 hour. The second ethyl acetate layer was removed and added to the first, and the combined ethyl acetate extracts wereconcentrated to an aqueoussuspension which was partitioned between equal volumes of waterchloroform -methanol (1.5 liters of each). The upper layer from this partition was extracted twice with further volumes of chloroform (0.7 liters each time) and these chloroform extracts were combined with the original lower layer and concentrated to an oil. This oil was chromatographed over a Sephadex LH-20 column (8cmx 80cm) eluted with methanol. Active fractions from this column were combined and concentrated to an oil. This oil was

Determination of the mechanism of action of FK506and cyclosporin A has yielded new molecular targets involved in signal transduction during T cell activation. A commontarget of FK506 and cyclosporin A is inhibition of activation of the NFATtranscription factor, for which a specific binding region is present in the promoter of the IL-2 gene. A reporter gene assay has been used to screen for agents that interfere with this early step in T cell activation. Simple aromatic compoundsthat block NFAT-dependent transcription and showin vitro immunosuppressiveactivity were isolated from the broth and mycelia of two Streptomyces sp. fermentations. The compounds were active at concentrations that were not directly cytotoxic.