Synthesis of (+)-laurencin via ring expansion of a C-glycoside derivative

Fujiwara, Kenshu; Yoshimoto, Saori; Takizawa, Ayumi; Souma, Shin-ichiro; Mishima, Hirofumi; Murai, Akio; Kawai, Hidetoshi; Suzuki, Takanori

doi:10.1016/j.tetlet.2005.08.024

Cited by 34 publications

(9 citation statements)

References 42 publications

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“…(3Z,9Z )-7-Chloro-6-hydroxy-12-oxo-pentadeca-3,9-dien-1-yne (706), the 6,9-epoxy acetogenins possess either a (E)-or (Z)-enyne moiety (712-716) or a bromoallene functionality (717)(718)(719)(720), whereas the 7,10-epoxy, the 9,12-epoxy and the 10,13-epoxy acetogenins exhibit a (E)-or (Z)-enyne moiety (721)(722)(723)(724)(725)(726)(727)(728)(729). Acetogenins containing two isolated tetrahydrofuran rings can either possess a bis(tetrahydrofuran-2-yl)methane (730 and 731) or a 2,2 0 -bistetrahydrofuran (732-738) core.…”

Section: Acetogeninsmentioning

confidence: 99%

The Laurencia Paradox: An Endless Source of Chemodiversity

Harizani

Iοannou

Roussis

2016

Progress in the Chemistry of Organic Natural Products

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Nature, the most prolific source of biological and chemical diversity, has provided mankind with treatments for health problems since ancient times and continues to be the most promising reservoir of bioactive chemicals for the development of modern drugs. In addition to the terrestrial organisms that still remain a promising source of new bioactive metabolites, the marine environment, covering approximately 70% of the Earth's surface and containing a largely unexplored biodiversity, offers an enormous resource for the discovery of novel compounds. According to the MarinLit database, more than 27,000 metabolites from marine macro- and microorganisms have been isolated to date providing material and key structures for the development of new products in the pharmaceutical, food, cosmeceutical, chemical, and agrochemical sectors. Algae, which thrive in the euphotic zone, were among the first marine organisms that were investigated as sources of food, nutritional supplements, soil fertilizers, and bioactive metabolites.Red algae of the genus Laurencia are accepted unanimously as one of the richest sources of new secondary metabolites. Their cosmopolitan distribution, along with the chemical variation influenced to a significant degree by environmental and genetic factors, have resulted in an endless parade of metabolites, often featuring multiple halogenation sites.The present contribution, covering the literature until August 2015, offers a comprehensive view of the chemical wealth and the taxonomic problems currently impeding chemical and biological investigations of the genus Laurencia. Since mollusks feeding on Laurencia are, in many cases, bioaccumulating, and utilize algal metabolites as chemical weaponry against natural enemies, metabolites of postulated dietary origin of sea hares that feed on Laurencia species are also included in the present review. Altogether, 1047 secondary metabolites, often featuring new carbocyclic skeletons, have been included.The chapter addresses: (1) the "Laurencia complex", the botanical description and the growth and population dynamics of the genus, as well as its chemical diversity and ecological relations; (2) the secondary metabolites, which are organized according to their chemical structures and are classified into sesquiterpenes, diterpenes, triterpenes, acetogenins, indoles, aromatic compounds, steroids, and miscellaneous compounds, as well as their sources of isolation which are depicted in tabulated form, and (3) the biological activity organized according to the biological target and the ecological functions of Laurencia metabolites.

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Section: Acetogeninsmentioning

confidence: 99%

The Laurencia Paradox: An Endless Source of Chemodiversity

Harizani

Iοannou

Roussis

2016

Progress in the Chemistry of Organic Natural Products

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“…We have reported the bromination and chlorination of the secondary alcohol (AE )-28 with the Ghosez reagents, 1-(halo-2-methylpropenyl)dimethylamines. [36,37] Interestingly, bromination of the alcohol (AE )-28 with carbon tetrabromide and trioctylphosphane [38] delivered a mixture of the bromides (AE)-30 and (AE )-31 presumably by means of neighbouringgroup participation of acetate involving the corresponding six-membered acetoxonium ion. Having demonstrated, in the racemic series, that it was indeed possible to introduce halogen atoms stereospecifically onto a medium-ring ether system that closely resembles the core structure of (+)-obtusenyne (1), we turned our attention to the elaboration of the trans-diol (À)-2.…”

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confidence: 99%

“…[65] We, therefore, reasoned that conversion of the diol (À)-40 into the dibromide (À)-62 would simultaneously introduce the secondary bromide required for obtusenyne and activate the primary hydroxyl in readiness for carbon-carbon bond formation. In the event, exposure of the diol (À)-40 to freshly purified carbon tetrabromide and freshly distilled trioctylphosphane in hot toluene [38] provided the requisite dibromide (À)-62 in 90 % yield (Scheme 15). Attempted coupling of the dibromide (À)-62 with various methylcuprates under a variety of conditions resulted either in no reaction, or in the formation of ring-opened products.…”

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confidence: 99%

“…Exposure of the alcohol to carbon tetrabromide and trioctylphosphane [38] provided the corresponding bromide (À)-38 in 70 % yield. The structure of the bromide (À)-38 was confirmed by single-crystal X-ray analysis, indicating that the bromination had occurred with inversion of configuration at C-3 ( Figure 8); [70] Murai has reported that the introduction of bromine in medium-ring ethers can occur with inversion or retention of configuration at the reacting centre depending on the conditions employed.…”

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confidence: 99%

“…Gratifyingly, upon treatment of the secondary alcohol (À)-79 with freshly purified carbon tetrabromide and freshly distilled trioctylphosphane in hot toluene, [38] the desired bromide (+)-80 was obtained in 67 % yield. Subsequent removal of the remaining hydroxyl protecting group furnished the bromo-alcohol (+)-81, an intermediate in Crimminss synthesis of (+)-obtusenyne ((+)-1).…”

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confidence: 99%

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Synthesis of (+)‐Obtusenyne

Mak

Curtis

Payne

et al. 2008

Chemistry A European J

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An enantioselective synthesis of the halogenated medium-ring ether natural product (+)-obtusenyne is reported which uses the ring expansion of a seven-membered ketene acetal by means of a Claisen rearrangement to construct the core nine-membered oxygen heterocycle. The trans substituents across the ether linkage were established by using a transition-metal-catalyzed intramolecular hydrosilation reaction of an exo-cyclic enol ether. In addition, a formal synthesis of ent-obtusenyne from 2-deoxy-D-ribose is reported. A number of interesting points regarding the chemistry of medium-ring oxygen heterocycles are highlighted.

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Olefin Ring‐Closing Metathesis

Yet

2016

Organic Reactions

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The olefin ring‐closing metathesis reaction catalyzed by ruthenium and molybdenum complexes has been employed in the syntheses of carbocycles, heterocycles, supramolecular compounds, and in tandem metathesis reactions. Chiral ruthenium and molybdenum catalysts have provided high enantiomeric and diastereomeric excesses in ring‐closing metathesis reactions. Many of the unsuccessful medium‐ and large‐sized ring formations which were unsuccessful by traditional methods, such as the intramolecular Wittig, Horner–Wadsworth–Emmons, and Julia–Kocienski reactions, can now be formed by olefin ring‐closing metathesis reactions. Ring‐closing metathesis has been a key step and sometimes the only successful method for the synthesis of numerous natural products and drug discovery targets. The objective of this chapter is to provide an updated, comprehensive coverage of the literature of the olefin ring‐closing metathesis reaction and related processes. Key mechanistic points are summarized.

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Synthesis of (+)-laurencin via ring expansion of a C-glycoside derivative

Cited by 34 publications

References 42 publications

The Laurencia Paradox: An Endless Source of Chemodiversity

The Laurencia Paradox: An Endless Source of Chemodiversity

Synthesis of (+)‐Obtusenyne

Olefin Ring‐Closing Metathesis

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