Improved Synthesis of the ABCDE Fragment of Brevetoxin A

Crimmins, Michael T.; McDougall, Patrick J.; Ellis, J. Michael

doi:10.1021/ol0615782

Cited by 32 publications

(19 citation statements)

References 25 publications

(22 reference statements)

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“…While new opportunities have explored the synthesis of medium-ring carbocycles using ring-closing metathesis,14 the formation of cyclononenes has presented problems for some RCM strategies 15. On the other hand, two groups have independently described recent results for Nozaki-Hiyama-Kishi cyclizations directed toward pestalotiopsin, a caryophyllene sesquiterpenoid 16.…”

Section: Introductionmentioning

confidence: 99%

Studies for the Synthesis of Xenicane Diterpenes. A Stereocontrolled Total Synthesis of 4-Hydroxydictyolactone

2009

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The stereocontrolled total synthesis of 4-hydroxydictyolactone (4), a member of the xenicane diterpene family of natural products, is described. These studies feature the development of the B-alkyl Suzuki cross-coupling reaction for direct access to (E)-cyclononenes from acyclic precursors. The Ireland-Claisen rearrangement is effectively utilized to establish the backbone asymmetry of the contiguous C2, C3, C10 stereotriad of 4. The synthesis strategy has devised an intramolecular Nozaki-Hiyama reductive allylation of a formate ester for the stereoselective formation of five-membered lactols 22. In addition, an internally directed SE' propargylation using allenylmagnesium bromide is described to establish the stereochemistry of the C4 alcohol in 27, and the terminal alkyne is subsequently functionalized via a regioselective syn-silylstannylation to yield 30. Finally, the stereocontrolled phenylselenylation of the ester enolate derived from 43 leads to the desired syn-oxidative elimination to yield the natural product 4.

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Section: Introductionmentioning

confidence: 99%

Studies for the Synthesis of Xenicane Diterpenes. A Stereocontrolled Total Synthesis of 4-Hydroxydictyolactone

2009

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“…Whereas this RCMbased strategy was highly appealing at the conceptual level, the successful implementation of this approach was much less certain as no literature precedent existed prior to our own work, for the direct construction of trans-fused bicyclo [7.4.0] systems by an RCM-mediated closure of a nine-membered ring. [11,12] The stereogenic center at C4a was envisioned to be created by substrate controlled 1,4-cuprate addition onto a,bunsaturated d-lactone I-3, which would be derived from diene I-2 by a second RCM reaction. Lastly, the stereocenter at C11a was to be set through a diastereoselective aldol reaction, thus leading to O-protected 3-hydroxy-propanal I-1 a and a suitable chiral crotonyl derivative I-1 b as the ultimate precursors.…”

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confidence: 99%

Total Synthesis of the Marine Diterpenoid Blumiolide C

et al. 2008

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First bloom: The total synthesis of the cytotoxic marine natural product blumiolide C (1) features a ring‐closing metathesis (RCM) for the closure of a nine‐membered ring to give the trans‐bicyclo[7.4.0]oxatridecene core (see scheme; PMB=para‐methoxybenzyl, TBS=tert‐butyldimethylsilyl). Attachment of the side chain at C4 of the bicyclic core was achieved in a highly stereoselective manner and excellent yield through an aldol reaction/elimination sequence.

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“…Our attempts failed when treating propionated oxazolidinone with Masamune's method [63,64] . During our investigation, Crimmins reported a direct intermolecular Claisen condensation of acylated oxazolidinone to β-ketoester using LDA as the base [36] . However, when this condition was applied to 8b, the yield of 9 was not satisfied.…”

Section: Resultsmentioning

confidence: 98%

“…Thus, development of a direct method is needed for such transformation. In the course of our investigation on synthesis of cystothiazole A, Crimmins et al [36] reported a Claisen condensation for a similar direct transformation. In this paper, we report an efficient route to cystothiazole A with application of the one-step transformation in the synthetic strategy developed by Williams et al [19] .…”

Section: Introductionmentioning

confidence: 87%