Abstract
The organic extract of the Caribbean sponge Smenospongia aurea has been shown to contain an array of novel chlorinated secondary metabolites derived from a mixed PKS-NRPS biogenetic route such as the smenamides. In this paper, we report the presence of a biogenetically different compound known as smenopyrone, which is a polypropionate containing two γ-pyrone rings. The structure of smenopyrone including its relative and absolute stereochemistry was determined by spectroscopic analysis (NMR, MS, ECD) and supported by a comparison with model compounds from research studies. Pyrone polypropionates are unprecedented in marine sponges but are commonly found in marine mollusks where their biosynthesis by symbiotic bacteria has been hypothesized and at least in one case demonstrated. Since pyrones have recently been recognized as bacterial signaling molecules, we speculate that smenopyrone could mediate inter-kingdom chemical communication between S. aurea and its symbiotic bacteria.
Highlights
Introduction γPyrones are a large class of biologically active compounds biosynthesized by polyketide synthases, multi-enzyme systems responsible for polyketide assembly through condensation of acyl-CoA units
In 2013, Gavagnin et al [4] reported a comprehensive study of polypropionates from marine pulmonate mollusks belonging to the family of Onchidiidae [5]
Earlier in 1996, auripyrones A and B were isolated from the Japanese sea hare Dolabella auricularia [6], which is a species known for being the first source of dolastatin-10 [7]
Summary
Islands) in June at −15 m by experts of our group [15]. Islands) in June 2013 at −15 m by experts of our group [15]. The proton NMR spectrum revealed the presence of nine nine methyl methylgroups groups(two (two triplets, doublets, andand three singlets) outout of 25 carbon atoms, which suggests a polypropionate structure. A groups on alternated carbon atoms, the HMBC correlations of methyl protons provided enough. Sole structure hydroxylof group in thewas molecule confirmed by the analysis ofthe theplanar fragment ions present in the tandem massconfirmed spectrum This completed structure of 1, which was further by the 4). The chemical shift of which is very similar to eight smenopyrone (1) with those of the corresponding carbons of synthetic models, i.e., eight diastereomers diastereomers of maurenone [19]very (4–11, 5). The chemical shiftsbyofmodel model compounds, weretheexpressed as the of the values of of chemical shift differences, Σ|Δδ|
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