Netamines A–G: seven new tricyclic guanidine alkaloids from the marine sponge Biemna laboutei

Sorek, Hagit; Rudi, Amira; Gueta, Sophie; Reyes, Fernando; Martín, María Jesús Sánchez; Aknin, Maurice; Gaydou, Émile M.; Vacelet, Jean; Kashman, Yoel

doi:10.1016/j.tet.2006.06.063

Cited by 41 publications

(36 citation statements)

References 20 publications

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“…The 1 H NMR data and 13 C NMR correspond to the literature data,8,44 except that our 1 H NMR data are 0.02 to 0.05 ppm upfield and our 13 C NMR data are all about 0.1 to 0.5 ppm shifted, possibly because of a slightly different extent of protonation.…”

Section: Methodssupporting

confidence: 86%

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Synthesis of 7-Epineoptilocaulin, Mirabilin B, and Isoptilocaulin. A Unified Biosynthetic Proposal for the Ptilocaulin and Batzelladine Alkaloids. Synthesis and Structure Revision of Netamines E and G

Pochapsky

Snider

2008

J. Org. Chem.

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Addition of guanidine to a 6-methylhexahydroindenone in MeOH at reflux afforded 7-epineoptilocaulin. A similar reaction with a 6-propylhexahydroindenone afforded netamine E. MnO 2 oxidation of 7-epineoptilocaulin and netamine E afforded mirabilin B and netamine G, respectively. The netamines have the side chains trans, not cis as was initially proposed. A unified biosynthetic scheme for the batzelladines and ptilocaulin family is proposed. Conjugate addition of guanidine to a bis enone followed by an intramolecular Michael reaction of the enolate to the other enone, aldol reaction, dehydration and enamine formation will lead to a tricyclic intermediate at the dehydroptilocaulin oxidation state. 1,4-Hydride addition will lead to ptilocaulin or 7-epineoptilocaulin depending on which face the hydride adds to. 1,2-Hydride addition will lead to isoptilocaulin. The key tricyclic intermediate was prepared from a tetrahydroindenone and guanidine and reduced with NaBH 4 to give a mixture rich in ptilocaulin and isoptilocaulin.

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Section: Methodssupporting

confidence: 86%

“…The 1 H NMR (CD 3 OD) and 13 C NMR (CD 3 OD) data correspond to the literature data,8 except that our 1 H NMR (CD 3 OD) data are 0.01 to 0.03 ppm upfield and our 13 C NMR (CD 3 OD) data are all about 0.1 to 0.4 ppm upfield.…”

Section: Methodssupporting

confidence: 85%

Synthesis of 7-Epineoptilocaulin, Mirabilin B, and Isoptilocaulin. A Unified Biosynthetic Proposal for the Ptilocaulin and Batzelladine Alkaloids. Synthesis and Structure Revision of Netamines E and G

Pochapsky

Snider

2008

J. Org. Chem.

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“…Misassignments of single stereocenters (Table 7) near to correctly assigned centers are associated with interpretation of NOE data for structurally diverse compounds. For example, this is the case for brevenal, 61, 62 solandelactones A-H, 63, 64 ritterazines B 65, 66 and F, 67 netamines E and G, 68, 69 briarellin J, 70, 71 and dictyosphaeric acid A. 72, 73 Consideration of the source of these errors highlights the need for careful evaluation of all possible alternative molecular models that adhere to NOE constraints.…”

Section: Sources Of Natural Product Structural Misassignmentsmentioning

confidence: 99%

Survey of marine natural product structure revisions: A synergy of spectroscopy and chemical synthesis

Suyama

Gerwick

McPhail

2011

Bioorganic & Medicinal Chemistry

166

175

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The structural assignment of new natural product molecules supports research in a multitude of disciplines that may lead to new therapeutic agents and or new understanding of disease biology. However, reports of numerous structural revisions, even of recently elucidated natural products, inspired the present survey of techniques used in structural misassignments and subsequent revisions in the context of constitutional or configurational errors. Given the comparatively recent development of marine natural products chemistry, coincident with the modern spectroscopy, it is of interest to consider the relative roles of spectroscopy and chemical synthesis in the structure elucidation and revision of those marine natural products which were initially misassigned. Thus, a tabulated review of all marine natural product structural revisions from 2005 to 2010 is organized according to structural motif revised. Misassignments of constitution are more frequent than perhaps anticipated by reliance on HMBC and other advanced NMR experiments, especially considering the full complement of all natural products. However, these techniques also feature prominently in structural revisions, specifically of marine natural products. Nevertheless, as is the case for revision of relative and absolute configuration, total synthesis is a proven partner for marine, as well as terrestrial, natural products structure elucidation. It also becomes apparent that considerable ‘detective work’ remains in structure elucidation, in spite of the spectacular advances in spectroscopic techniques.

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“…[1][2][3] In nature guanidine occurs as cycles and has been proven to be an effective antifungal or antibacterial material. [4] Although little has been achieved in terms of the synthesis and use of ring guanidines as ligands or for catalysis, a few synthetic ring guanidine molecules and their derivatives are known. They are used as anticancer agents [5] and as catalysts in asymmetric synthesis, [6] e.g., for the 1,4-addition of 1,3-dicarbonyl compounds with nitro-alkenes or in the synthesis of amino nitriles.…”

Section: Introductionmentioning

confidence: 99%

Phantom Ring‐Closing Condensation Polymerization: Towards Antibacterial Oligoguanidines

Mattheis

Schwarzer

Frenking

et al. 2011

Macromol. Rapid Commun.

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The first example of phantom ring-closing condensation polymerization for the synthesis of oligoguanidines is presented. A new oligoguanidine with a ring structure was achieved in one step by the condensation reaction of a triamine, like diethylenetriamine, with guanidine hydrochloride. The condensation reaction proceeded by selective ring-closure towards the formation of five-membered rings in the oligomer backbone. The resulting polymer repeat unit structure was different from the starting monomers (phantom polymer) and was formed by elimination of three molecules of ammonia per repeat unit. The inter-, intra-, and inter-molecular reaction sequences led to the new structure as proved by different spectroscopic techniques (atmospheric pressure chemical-ionization mass spectrometry, and one-dimensional and two-dimensional homo- and heteronuclear correlation NMR experiments) as well as supported by quantum chemical investigations. Preliminary results regarding antibacterial use of the resulting oligoguanidine were also promising and showed its effect within 15-30 min as an antibacterial material.

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Netamines A–G: seven new tricyclic guanidine alkaloids from the marine sponge Biemna laboutei

Cited by 41 publications

References 20 publications

Synthesis of 7-Epineoptilocaulin, Mirabilin B, and Isoptilocaulin. A Unified Biosynthetic Proposal for the Ptilocaulin and Batzelladine Alkaloids. Synthesis and Structure Revision of Netamines E and G

Synthesis of 7-Epineoptilocaulin, Mirabilin B, and Isoptilocaulin. A Unified Biosynthetic Proposal for the Ptilocaulin and Batzelladine Alkaloids. Synthesis and Structure Revision of Netamines E and G

Survey of marine natural product structure revisions: A synergy of spectroscopy and chemical synthesis

Phantom Ring‐Closing Condensation Polymerization: Towards Antibacterial Oligoguanidines

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