26 research outputs found
Studies on Polyethers Produced by Red Algae
Get PDFTwo novel squalene-derived triterpenes, spirodehydrovenustatriol (3) and 14-keto-dehydrothyrsiferol (4) were isolated from the red alga Laurencia viridis, together with two new and unusual C17 terpenoids, adejen A (5) and B (6). These truncated structures possess structural similarities with other known squalene metabolites and their biogenetic origin has been proposed on the basis of an oxidative process of the squalene skeleton. All the structures were elucidated by extensive use of 2D NMR spectroscopic methods
New Polyether Triterpenoids from Laurencia viridis and Their Biological Evaluation
Get PDFThe red seaweed Laurencia viridis is a rich source of secondary metabolites derived from squalene. New polyethers, such as iubol (2), 22-hydroxy-15(28)- dehydrovenustatriol (3), 1,2-dehydropseudodehydrothyrsiferol (4), and secodehydrothyrsiferol (5) have been isolated and characterized from this alga. The structures were determined through the interpretation of NMR spectroscopic data and the relative configuration was proposed on the basis of NOESY spectrum and biogenetic considerations. All new compounds exhibited significant cytotoxic activity against a panel of cancer cell lines
New Oxidized Zoanthamines From a Canary Islands Zoanthus Sp
Get PDFThree new norzoanthamine-type alkaloids, named 2-hydroxy-11-ketonorzoan thamide B (1), norzoanthamide B (2) and 15-hydroxynorzoanthamine (3), were isolated from Zoanthus sp. specimens collected at the Canary Islands. Their structures were determined by interpretation of NMR and HR-ESIMS data. Relative configurations of their chiral centers were proposed on the basis of ROESY spectra and by comparison of their spectroscopic data with those of the well-known compound, norzoanthamine.Peer reviewe
Zoaramine, a Zoanthamine-like Alkaloid with a New Skeleton
No full textChemical investigation of an Atlantic variety of Zoanthus sp. led to the isolation of two new metabolites, zoaramine and zoarenone. Their structures were deduced by the use of NMR spectroscopy and computational calculation of 1H and 13C chemical shifts. The core of these novel compounds resembles the structure of norzoanthamine alkaloids, and their isolation represents an important step toward a better understanding of the biogenetic origin of this group of antiosteoporotic molecules.Peer reviewe
Sclerin, a New Cytotoxic Cyclononapeptide from <i>Annona scleroderma</i>
No full textA new cytotoxic cyclononapeptide, sclerin, cyclo(⁻Dab1⁻Ser2⁻Tyr3⁻Gly4⁻Thr5⁻Val6⁻Ala7⁻ Ile8⁻Pro9⁻) (1), was isolated from the methanol extract of the seeds of Annona scleroderma, together with the known metabolite, cyclosenegalin A, cyclo(⁻Pro1⁻Gly2⁻Leu3⁻Ser4⁻Ala5⁻Val6⁻Thr7⁻) (2). The planar structures for the two compounds were established by comprehensive analysis of NMR and ESI-HRMS data, and the absolute stereochemistry was stablished by Marfey’s method. Compound 1 showed moderate cytotoxic activity against the human prostate carcinoma cell line DU-145 at µM concentration
Connecting Discrete Stereoclusters by Using DFT and NMR Spectroscopy: The Case of Nivariol
No full textThe structural determination of small organic molecules is mainly undertaken by using NMR techniques, although it is increasingly supplemented by using computational methods. NMR parameters, such as chemical shifts and coupling constants, are extremely sensitive indicators of local molecular conformation and are a source of structural evidence. However, their interpretation is fairly challenging in many circumstances, such as the case of the new polyether squalene derivative nivariol, the structure of which was elucidated by means of NMR spectroscopy and DFT calculations. The potential flexibility of this molecule and the high number of quaternary carbon atoms that it contains make its configurational assignment very difficult. Moreover, the relative configuration of four separated stereoclusters was established and subsequently connected by using NOE and J ‐based analysis, as well as by a comparison of its experimental 13C NMR chemical shifts with the corresponding population‐weighted values, as calculated by using DFT methods. Limitations of these used approaches became apparent but were overcome by combining the two methods.Peer reviewe
Zoaramine, a Zoanthamine-like Alkaloid with a New Skeleton
No full textChemical investigation of an Atlantic
variety of <i>Zoanthus </i>sp. led to the isolation of two
new metabolites, zoaramine and zoarenone.
Their structures were deduced by the use of NMR spectroscopy and computational
calculation of <sup>1</sup>H and <sup>13</sup>C chemical shifts. The
core of these novel compounds resembles the structure of norzoanthamine
alkaloids, and their isolation represents an important step toward
a better understanding of the biogenetic origin of this group of antiosteoporotic
molecules
Cytotoxic oxasqualenoids from the red alga Laurencia viridis
No full textThree new polyether squalene derivatives 15-dehydroxythyrsenol A (2), prethyrsenol A (3) and 13-hydroxyprethyrsenol A (4) have been isolated from the red alga Laurencia viridis. Their structures were determined through the interpretation of NMR spectroscopic data and chemical correlations. In addition, four semi-synthetic compounds modulating the solubility of the lead compound dehydrothyrsiferol (1) were prepared without loss of activity. The cytotoxicity of the new compounds exhibited low μM activities. In order to explain their biological properties, docking simulations of the natural and synthetic compounds onto the αvβ3 integrin binding region were carried out. © 2011 Elsevier Masson SAS. All rights reserved.Financial support was provided by the grants CTQ2008-06754- C04-01 and SAF2008-02251 (MEC); C2008000145 and EXMAR (ACISII); RD06/0020/1037 from Red Temática de Investigación Cooperativa en Cáncer, Instituto de Salud Carlos III, co-funded by the Fondo Europeo de Desarrollo Regional of the European Union, and Junta de Castilla y León (GR15-Experimental Therapeutics and Translational Oncology Program, and Biomedicine Project 2009) and F.C.P. is the recipient of a SEGAI-ULL fellowship.Peer Reviewe
