Untitled

Guella, Graziano; Mancini, Ines; Öztunç, Aysel; Pietra, Francesco

doi:10.1002/(sici)1522-2675(20000216)83:2<336::aid-hlca336>3.3.co;2-i

Cited by 14 publications

(36 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…259,340−342 The placement of the bromine atom at C 7 and chlorine atom at C 13 for obtusallenes V−VII (545−547) was originally assigned by NMR spectroscopic analysis. 341 However, the results from GIAO-based density functional prediction revealed that the positions of the halogen atoms at C 7 and C 13 in these compounds should be reversed. 342 These results again indicated the challenge for the structure assignment by NMR spectral analysis of bromochlorinated metabolites.…”

Section: Halogenated Nonterpenoid C 15 -Acetogenins (Acgs)mentioning

confidence: 99%

See 1 more Smart Citation

Halogenated Organic Molecules of Rhodomelaceae Origin: Chemistry and Biology

et al. 2013

View full text Add to dashboard Cite

show abstract

Section: Halogenated Nonterpenoid C 15 -Acetogenins (Acgs)mentioning

confidence: 99%

“…341 Collecting 1 H NMR spectra in different NMR solvents might be a solution of the problem of signal superimposition. 341 4.5.11. ACGs of the Maneonene and Isomaneonene Classes.…”

Section: Halogenated Nonterpenoid C 15 -Acetogenins (Acgs)mentioning

confidence: 99%

Halogenated Organic Molecules of Rhodomelaceae Origin: Chemistry and Biology

et al. 2013

View full text Add to dashboard Cite

show abstract

“…The latter may be altered significantly by different heteroatom substituents, as for the bromo-substituted obtusallenes V–VII 135–137 (Tables 2 and 7). Similarly, NOE data analyses (iejimalides, 138–140 scleritodermin A, 141, 142 Table 9) may be ambiguous for endocyclic double bonds if the structural constraints of the ring are not well defined.…”

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

164

175

View full text Add to dashboard Cite

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.

show abstract

“…Finally, extensive NMR experiments on an authentic sample of obtusallene V led to an identical interpretation to that of Guella. 9 Thus, 13 C NMR analysis showed a resonance with a chemical shift of 57 ppm corresponding to C-7 and the carbon at C-13…”

Section: Scheme 2 Preparation Of Ring-closing Metathesis Substrate 12mentioning

confidence: 99%

Bromonium Ion Induced Transannular Oxonium Ion Formation−Fragmentation in Model Obtusallene Systems and Structural Reassignment of Obtusallenes V−VII

et al. 2009

View full text Add to dashboard Cite

Ring-closing metathesis was used to construct the strained 11-membered ring of obtusallenes II (and IV). Bromonium-ion induced transannular oxonium ion formation-fragmentation gave the macrocyclic carbon skeleton of obtusallene VII with a bromine atom at C-13 in line with a previously published hypothesis. An additional brominated [5.5.1]bicyclotridecane adduct that must arise from a bromonium-ion induced transannular oxonium ion formation-fragmentation could also be isolated, suggesting that this adduct represents the core of an as yet undiscovered natural product. An authentic sample of obtusallene V was studied by NMR spectroscopy and the position of the halogens at C-7 and C-13 were reassigned on the basis of a 13 C NMR chlorine-induced isotopic shift. This revised structure was subsequently confirmed by X-ray crystallography. These findings allow us to confidently conclude that the structures of obtusallenes VII and VI should also be reassigned.

show abstract

Untitled

Cited by 14 publications

References 0 publications

Halogenated Organic Molecules of Rhodomelaceae Origin: Chemistry and Biology

Halogenated Organic Molecules of Rhodomelaceae Origin: Chemistry and Biology

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

Bromonium Ion Induced Transannular Oxonium Ion Formation−Fragmentation in Model Obtusallene Systems and Structural Reassignment of Obtusallenes V−VII

Contact Info

Product

Resources

About