RESUMO
The absolute stereostructures of the components of symplocin A (3), a new N,N-dimethyl-terminated peptide from the Bahamian cyanobacterium Symploca sp., were assigned from spectroscopic analysis, including MS, 2D NMR, and Marfey's analysis. The complete absolute configuration of symplocin A, including the unexpected D-configurations of the terminal N,N-dimethylisoleucine and valic acid residues, was assigned by chiral-phase HPLC of the corresponding 2-naphthacyl esters, a highly sensitive, complementary strategy for assignment of N-blocked peptide residues where Marfey's method is ineffectual or other methods fall short. Symplocin A exhibited potent activity as an inhibitor of cathepsin E (IC(50) 300 pM).
Assuntos
Catepsina E/antagonistas & inibidores , Cianobactérias/química , Naftalenos/química , Peptídeos/isolamento & purificação , Bahamas , Cromatografia Líquida de Alta Pressão , Ésteres , Concentração Inibidora 50 , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Peptídeos/química , Peptídeos/farmacologiaRESUMO
The complete stereostructures of xestoproxamines A-C, from the Bahamian sponge Neopetrosia proxima, were assigned from spectroscopic analysis, including MS, 2D NMR, and integrated degradation-CD analysis. Two new CD application protocols are described for defining absolute configuration: one for allylic methyl groups in branched chains and a second for the heterocyclic core bis-piperidine with specific applicability to other members of this class alkaloids--known for their stereoheterogeneity--and tertiary cyclic amines in general.
Assuntos
Alcaloides/química , Alcaloides/isolamento & purificação , Piperidinas/química , Piperidinas/isolamento & purificação , Poríferos/química , Aminas/química , Aminas/isolamento & purificação , Animais , Bahamas , Dicroísmo Circular , Modelos Moleculares , Estrutura Molecular , Ressonância Magnética Nuclear BiomolecularRESUMO
Long-chain polyacetylene alcohols, faulknerynes A-C, along with known compounds diplynes A, C and E, were isolated from two specimens of the encrusting sponge, Diplastrella sp., collected from the surface of coral in the Bahamas. Two CD methods were critically evaluated for their suitability to terminal propargylic glycols and applied to assignment of configurations of faulkneryne A and diplyne C.