Synthetic Study of Marine Polycyclic Ethers: Total Synthesis of Hemibrevetoxin B.

Nakata, Tadashi

doi:10.5059/yukigoseikyokaishi.56.940

Cited by 16 publications

(5 citation statements)

References 13 publications

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“…[27][28][29][30][31][32] In 1997, Nakata and co-workers reported that introduction of a styryl group adjacent to the epoxide provided greater stabilisation in the 6-endo transition state compared with the alkenic epoxides. 33,34 Treatment of trans-epoxides containing a styryl group with either acid or base generated THP products in excellent yield, but improved stereocontrol was achieved using NaH (entries 1 and 2, Table 1). Whilst Nicolaou reported that unsaturated cis-epoxides gave poor 6-endo selectivity under acidic conditions, 23 Nakata showed that styryl epoxides may be converted solely to THP products under acidic conditions, with no evidence for the formation of the corresponding THF (entries 3 and 4, Table 1).…”

Section: Reviewmentioning

confidence: 99%

“…This methodology was used in the synthesis of a model compound 170 with the ST rings of maitotoxin (Scheme 37). 34,97 Zinc acetate in refluxing acetic acid was required for the ring expansion of mesylates 166 and 169. However, Nakata showed that by using chloromethylsulfonate (Mc) as the leaving group, rather than mesylate, ring expansion was achieved without the need for acetic acid (Scheme 38).…”

Section: Expansion Of Thf Ringsmentioning

confidence: 99%

“…95 Scheme 37 Synthesis of model ST rings of maitotoxin. 34,97 Scheme 38 Alternative conditions for the rearrangement-ring expansion of 5-exo product 171. Mc = chloromethylsulfonate.…”

Section: Expansion Of Thf Ringsmentioning

confidence: 99%

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Synthetic and biosynthetic methods for selective cyclisations of 4,5-epoxy alcohols to tetrahydropyrans

et al. 2022

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Section: Reviewmentioning

confidence: 99%

Section: Expansion Of Thf Ringsmentioning

confidence: 99%

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Synthetic and biosynthetic methods for selective cyclisations of 4,5-epoxy alcohols to tetrahydropyrans

et al. 2022

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“…When treated with Jacobsen catalyst 148 - 4 , diepoxide 148 - 1 was selectively transformed to diol 148 - 2 in 98% yield. This diol was efficiently protected to form 148 - 3 , intercepting a late-stage intermediate in Nakata’s total synthesis of hemibrevetoxin ( 148 - 5 ) …”

Section: The Jacobsen Hydrolytic Kinetic Resolutionmentioning

confidence: 99%

“…This diol was efficiently protected to form 148-3, intercepting a late-stage intermediate in Nakata's total synthesis of hemibrevetoxin . 801 The hydrolytic kinetic resolution of epoxides has been widely employed in the early steps of many total syntheses to generate enantiopure epoxide or epoxide-derived starting materials. The generality of this resolution has led to its widespread adoption; Jacobsen has written that "virtually every terminal epoxide examined to date [undergoes] clean and highly selective resolution."…”

Section: The Jacobsen Hydrolytic Kineticmentioning

confidence: 99%

Methods Utilizing First-Row Transition Metals in Natural Product Total Synthesis

2017

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First-row transition-metal-mediated reactions constitute an important and growing area of research due to the low cost, low toxicity, and exceptional synthetic versatility of these metals. Currently, there is considerable effort to replace existing precious-metal-catalyzed reactions with first-row analogs. More importantly, there are a plethora of unique transformations mediated by first-row metals, which have no classical second- or third-row counterpart. Herein, the application of first-row metal-mediated methods to the total synthesis of natural products is discussed. This Review is intended to highlight strategic uses of these metals to realize efficient syntheses and highlight the future potential of these reagents and catalysts in organic synthesis.

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First Desymmetrization of a Centrosymmetric Molecule in Natural Product Synthesis: Preparation of a Key Fragment in the Synthesis of Hemibrevetoxin B

2001

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Many polyether marine natural products, such as the ciguatoxins, brevetoxins, and yessotoxins, have embedded centrosymmetric fragments. [1] For example, the AB ring system of hemibrevetoxin B (1) is a centrosymmetric dioxepane (see boxed fragment: 1, Scheme 1). There are three reported syntheses of hemibrevetoxin B (1), but none of these approaches take advantage of this hidden symmetry. [2, 3] Scheme 1. Retrosynthetic analysis.Our approach to hemibrevetoxin B is outlined in Scheme 1. Desymmetrization [4] of the centrosymmetric diepoxide 3, by selective hydrolysis [5] of one of its enantiotopic epoxides and protection, would give the known [3] acetonide 2. The symmetry of 3 demanded that a two-directional strategy [6] be used, an approach which was expected to improve the efficiency of the synthesis of 2 considerably. The epoxide 2 has been prepared Substitution of a methyl group for the N-hydrogen atom turns a conformationally floppy adsorbate into a sterically constrained one. This alters the process of intramolecular vibrational energy redistribution (IVR). For pyrrolidine, the CH 2 stretch excitation can dissipate by coupling to the large-scale conformational change. This dissipation path is quenched for N-methylpyrrolidine. For both molecules, the CH 2 stretch can transfer its energy to other lower energy vibrations, substrate phonons, and electron ± hole pairs.Like the pyrrolidines, pyridine binds to copper predominantly through the lone pair electrons on nitrogen. [20] Only the CH (CD) stretch mode of pyridine on Cu(001) at 377 (281) mV has been observed with STM-IETS, [21] and the lineshape of this mode matches the lineshape of the Nmethylpyrrolidine CH 2 stretch. The aromaticity of the pyridine ring constrains the molecule to a planar geometry. The rigid electronic backbone of pyridine acts like the bulky methyl group on N-methylpyrrolidine, keeping the molecule in just one conformation.It is evident that molecular structure can have a significant impact on the dissipation of vibrational energy. Simple substitution of a methyl group for a hydrogen atom removes the NDR from the I ± V curve. Thus, as we move to ever smaller devices, consideration must be given to the effect of molecular structure and conformation on the conductivity. By changing the functional groups in a molecule, different electronic functions can be realized at the molecular level. At a more fundamental level, understanding how molecular structure and dynamics alter electron transport through single molecules has important ramifications in chemical and biological systems.

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Synthetic Study of Marine Polycyclic Ethers: Total Synthesis of Hemibrevetoxin B.

Cited by 16 publications

References 13 publications

Synthetic and biosynthetic methods for selective cyclisations of 4,5-epoxy alcohols to tetrahydropyrans

Synthetic and biosynthetic methods for selective cyclisations of 4,5-epoxy alcohols to tetrahydropyrans

Methods Utilizing First-Row Transition Metals in Natural Product Total Synthesis

First Desymmetrization of a Centrosymmetric Molecule in Natural Product Synthesis: Preparation of a Key Fragment in the Synthesis of Hemibrevetoxin B

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