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Names | |
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IUPAC name (3S,7S,8R,12R,17R,19R,21R,25R)-23-chloro-3,12,17,19,21-pentahydroxy-8-methoxy-5-methyl-2,10,24,26-tetraoxaheptacyclo[11.8.2.27,7.14,18.01,18.016,22.03,25]hexacosa-4,13(23),14,16(22)-tetraene-6,9-dione | |
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Properties | |
C24H23ClO12 | |
Molar mass | 538.89 g·mol−1 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Sporolides A and B are polycyclic macrolides extracted from the obligate marine bacterium Salinispora tropica , which is found in ocean sediment. They are composed of a chlorinated cyclopenta[a]indene ring and a cyclohexenone moiety. [1] They were the second group of compounds (after salinosporamide A) isolated from Salinispora , and were said to indicate the potential of marine actinomycetes as a source of novel secondary metabolites. [2] The structures and absolute stereochemistries of both metabolites were elucidated using a combination of NMR spectroscopy and X-ray crystallography.
The complex aromatic structure of the sporolides was hypothesized to be derived from an unstable nine-membered ring enediyne precursor, which could undergo Bergman cyclization to generate a para-benzyne intermediate. Nucleophilic attack by chloride would account for the 1:1 mixture of sporolide A and B and for the single chlorine in these enediyne-derived natural products. This proposed mechanism was demonstrated in laboratory experiments, [3]
The biosynthesis of sporolide A and B is related to that of enediynes such as dynemicin A [4] and is proposed to proceed as shown below. [1] [3]
The first total synthesis of sporolide B was reported by K. C. Nicolaou's group and used a highly stereoselective and convergent strategy that involved two cycloaddition reactions. The first was a ruthenium-catalyzed intermolecular [2+2+2] cycloaddition reaction between two acetylenic units, A and B, and the second a thermally induced intramolecular [4+2] cycloaddition reaction between an o-quinone and the tetrasubstituted olefin within the intermediate, forming the macrocyclic structure of the target product. [5] [6]