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A soil Streptomycesnov. sp. (MST-115088) isolatedfrom semiarid terrain near Wollogorang Station, Queensland, returnedtwo known and two new examples of a rare class of cyclic hexapeptide,desotamides A and B (1and 2) and E andF (3and 4), respectively, together withtwo new d-Orn homologues, wollamides A and B (5and 6). Structures were assigned by detailed spectroscopicand C3Marfey’s analysis. The desotamides/wollamidesexhibit growth inhibitory activity against Gram-positive bacteria(IC500.6–7 μM) and are noncytotoxic to mammaliancells (IC50>30 μM). The wollamides exhibit antimycobacterialactivity (IC502.8 and 3.1 μM), including reductionin the intracellular mycobacterial survival in murine bone marrow-derivedmacrophages. [ABSTRACT FROM AUTHOR]

Seven new antibacterials, motualevic acids A−F (1−6) and (4E)-(R)-antazirine (7), have been isolated from the marine sponge Siliquariaspongiasp. and their structures elucidated by spectroscopic methods. Motualevic acids A−D are the first glycyl conjugates of the ω-brominated lipid (E)-14,14-dibromotetradeca-2,13-dienoic acid, and motualevic acid F is the first long-chain 2H-azirine 2-carboxylic acid to be found in nature. Carboxylic acid-containing compounds 1and 6inhibit the growth of Staphylococcus aureusand methicillin-resistant S. aureusat 1.2−10.9 μg/mL. [ABSTRACT FROM AUTHOR]