The structural peculiarity of saraines A, B and C, wherein a zwitterionic-like form is present due to the coordination of a nitrogen atom to the C-2 aldehyde by a strong proximity effect, has been further extended by experimental and theoretical evidences. They include the detection of [2M + H]+ clusters in electrospray ionization mass spectrometry in the positive ion mode of a water/acetonitrile solution, whereas only signals corresponding to [M + H]+ ions are detectable after addition of trifluoroacetic acid to the same solution. The zwitterionic form can be trapped to give O-methyl derivatives only by reaction with a strong alkylating agent such as Meerwein's reagent. DFT calculations carried out on the core structural model suggest that the nucleophilic N-1 atom in the minimized conformation is at a suitable distance from the carbonyl group and also defines an approach angle in good agreement with the Bürgi-Dunitz model. Antibacterial and hemolytic activities and inhibition of acetylcholinesterase (AChE) assays have been evaluated for saraines A-C in comparison to those of saraines 1-3 and isosaraine 1, all the metabolites isolated from the sponge Reniera (Haliclona) sarai collected in the Northern Adriatic sea
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Titolo: | New structural insights into saraines A, B and C, macrocyclic alkaloids from the mediterranean sponge Reniera (Haliclona) sarai |
Autori Unitn: | |
Anno di pubblicazione: | 2011 |
Titolo del periodico: | |
Citazione: | New structural insights into saraines A, B and C, macrocyclic alkaloids from the mediterranean sponge Reniera (Haliclona) sarai / A. Defant; I.Mancini; L. Raspor; G. Guella; T. Turk; K. Sepcic. - In: EUROPEAN JOURNAL OF ORGANIC CHEMISTRY. - ISSN 1434-193X. - STAMPA. - 2011/20,21(2011), pp. 3761-3767. |
Abstract: | The structural peculiarity of saraines A, B and C, wherein a zwitterionic-like form is present due to the coordination of a nitrogen atom to the C-2 aldehyde by a strong proximity effect, has been further extended by experimental and theoretical evidences. They include the detection of [2M + H]+ clusters in electrospray ionization mass spectrometry in the positive ion mode of a water/acetonitrile solution, whereas only signals corresponding to [M + H]+ ions are detectable after addition of trifluoroacetic acid to the same solution. The zwitterionic form can be trapped to give O-methyl derivatives only by reaction with a strong alkylating agent such as Meerwein's reagent. DFT calculations carried out on the core structural model suggest that the nucleophilic N-1 atom in the minimized conformation is at a suitable distance from the carbonyl group and also defines an approach angle in good agreement with the Bürgi-Dunitz model. Antibacterial and hemolytic activities and inhibition of acetylcholinesterase (AChE) assays have been evaluated for saraines A-C in comparison to those of saraines 1-3 and isosaraine 1, all the metabolites isolated from the sponge Reniera (Haliclona) sarai collected in the Northern Adriatic sea |
Handle: | http://hdl.handle.net/11572/88118 |
Appare nelle tipologie: | 03.1 Articolo su rivista (Journal article) |
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