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Reassignment of the absolute configuration of plakinidone from the sponge consortium Plakortis halichondrioides-Xestospongia deweerdtae using a combination of synthesis and a chiroptical approach.

ABSTRACT: Recent work by Wu et al. in connection with the first synthesis of the marine natural product plakinidone revealed that the most salient feature of its purported structure, a six-membered perlactone moiety, was in fact a five-membered lactone, i.e. a 3-methyl-4-hydroxy-2(5H)-furanone or tetronic acid ring. With the planar structure of plakinidone confidently revised, we undertook a new investigation to unambiguously establish its absolute configuration. Upon preparing two stable derivatives 1 and 5 from a sample of naturally occurring plakinidone extracted from the sponge association Plakortis halichondriodes-Xetospongia deweerdtae, the absolute configuration was assigned by synthesis and vibrational and electronic circular dichroism (VCD and ECD) measurements in combination with density functional theory calculations at the B3LYP/aug-cc-pVDZ/PCM(CH3CN) level of theory. Our combined efforts and the agreement between the experimental and calculated VCD/ECD spectra of 1 revealed that the absolute configuration of plakinidone was in fact (11S,17R) and not the formerly reported (11S,17S) diastereomer assigned by Wu et al.. Therefore, we propose that natural plakinidone is accurately represented by structure 12.

SUBMITTER: Jimenez-Romero C

PROVIDER: S-EPMC5295471 | biostudies-literature | 2016 Jun

REPOSITORIES: biostudies-literature

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Reassignment of the absolute configuration of plakinidone from the sponge consortium <i>Plakortis halichondrioides-Xestospongia deweerdtae</i> using a combination of synthesis and a chiroptical approach.

Jiménez-Romero Carlos C Rode Joanna E JE Rodríguez Abimael D AD

Tetrahedron, asymmetry 20160407 9-10

Recent work by Wu et al. in connection with the first synthesis of the marine natural product plakinidone revealed that the most salient feature of its purported structure, a six-membered perlactone moiety, was in fact a five-membered lactone, i.e. a 3-methyl-4-hydroxy-2(5H)-furanone or tetronic acid ring. With the planar structure of plakinidone confidently revised, we undertook a new investigation to unambiguously establish its absolute configuration. Upon preparing two stable derivatives <b>1 ...[more]

PMID: 28190935

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Project description:The recently described epizoic sponge-sponge symbioses between Xestospongia deweerdtae and two species of Plakortis present an unusual series of sponge interactions. Sponges from the genus Plakortis are fierce allelopathic competitors, rich in cytotoxic secondary metabolites, and yet X. deweerdtae flourishes as an epizoic encrustation on Plakortis deweerdtaephila and Plakortis symbiotica. Our objective in this study was to evaluate the hypothesis that X. deweerdtae grows epizoic to these two species of Plakortis due to a shared chemical defense against predators. We collected free-living individuals of X. deweerdtae and symbiotic pairs from a wide geographical range to generate crude organic extracts and a series of polarity fractions from sponge extract. We tested the deterrency of these extracts against three common coral reef predators: the bluehead wrasse, Thalassoma bifasciatum, the Caribbean sharpnose puffer, Canthigaster rostrata, and the white spotwrist hermit crab, Pagurus criniticornis. While the chemical defenses of P. deweerdtaephila and P. symbiotica are more potent than those of X. deweerdtae, all of the sponge species we tested significantly deterred feeding in all three generalist predators. The free-living form of X. deweerdtae is mostly defended across the region, with a few exceptions. The associated form of X. deweerdtae is always defended, and both species of Plakortis are very strongly defended, with puffers refusing to consume extract-treated pellets until the extract was diluted to 1/256× concentration. Using diode-array high performance liquid chromatography (HPLC) coupled with high-resolution mass spectrometry (LC-MS/IT-TOF), we found two secondary metabolites from P. deweerdtaephila, probably the cyclic endoperoxides plakinic acid I and plakinic acid K, in low concentrations in the associated-but not the free-living-form of X. deweerdtae, suggesting a possible translocation of defensive chemicals from the basibiont to the epibiont. Comparing the immense deterrency of Plakortis spp. extracts to the extracts of X. deweerdtae gives the impression that there may be some sharing of chemical defenses: one partner in the symbiosis is clearly more defended than the other and a small amount of its defensive chemistry may translocate to the partner. However, X. deweerdtae effectively deters predators with its own defensive chemistry. Multiple lines of evidence provide no support for the shared chemical defense hypothesis. Given the diversity of other potential food resources available to predators on coral reefs, it is improbable that the evolution of these specialized sponge-sponge symbioses has been driven by predation pressure.

Dataset Information

Reassignment of the absolute configuration of plakinidone from the sponge consortium Plakortis halichondrioides-Xestospongia deweerdtae using a combination of synthesis and a chiroptical approach.

Publications

Reassignment of the absolute configuration of plakinidone from the sponge consortium <i>Plakortis halichondrioides-Xestospongia deweerdtae</i> using a combination of synthesis and a chiroptical approach.

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