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Characterization of Calcification Events Using Live Optical and Electron Microscopy Techniques in a Marine Tubeworm
Published on: February 28, 2017
A new structural theme in the imidazole-containing alkaloids from a calcareous Leucetta sponge
1Department of Chemistry and Biochemistry and Institute of Marine Sciences, University of California, Santa Cruz, California 95064, USA.
Abstract:
Further study of the Fijian sponge Leucetta sp., a source of (+)-calcaridine A (4) and (-)-spirocalcaridines A (5) and B (6), has yielded (-)-spiroleucettadine (8), the first natural product to contain a fused 2-aminoimidazole oxalane ring along with the known compounds N,N-dimethylnaamidine D (3) and isonaamine B (7). NMR analysis allowed the unambiguous 2D structural assignment of 8, and its relative stereochemistry was determined by ROESY data. Good antibacterial activity was observed for 8 against Enterococcus durans with an MIC of less than 6.25 microg/mL.
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Isomers are different chemical species that have the same chemical formula. Structural isomerism of coordination compounds can be divided into two subcategories, the linkage isomers and coordination-sphere isomers.
Linkage isomers occur when the coordination compound contains a ligand that can bind to the transition metal center through two different atoms. For example, the CN− ligand can bind through the carbon atom or through the nitrogen atom. Similarly, SCN− can be...
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