- Enantioselective synthesis and stereochemical determination of the highly reduced polyketide ishigamide
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Ishigamide was isolated as a metabolite of a recombinant strain of Streptomyces sp. MSC090213JE08 and its unsaturated fatty acid moiety has been confirmed in vitro to be synthesized by a type II PKS. Biosynthesis of such a highly reduced polyketide by a type II PKS is worthy of note. However, absolute configuration of ishigamide remained unknown. (R)-Ishigamide was synthesized enantioselectively employing Stille coupling and Wittig reaction between three units, vinyl iodide, stannyldienal, and Wittig salt. Stereochemistry of natural ishigamide was determined to be R by chiral HPLC analysis comparing with the synthesized standard.
- Du, Danyao,Ishigami, Ken,Katsuta, Ryo,Katsuyama, Yohei,Nukada, Tomoo,Ohnishi, Yasuo,Seo, Mitsuki,Yajima, Arata
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p. 148 - 153
(2022/03/18)
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- A Synthesis of Alsmaphorazine B Demonstrates the Chemical Feasibility of a New Biogenetic Hypothesis
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An N-oxide fragmentation/hydroxylamine oxidation/intramolecular 1,3-dipolar cycloaddition cascade efficiently converted an oxidized congener of akuammicine into the complex, hexacyclic architecture of the alsmaphorazine alkaloids. This dramatic structural change shows the chemical feasibility of our novel proposal for alsmaphorazine biogenesis. Critical to these endeavors was a marked improvement in our previously reported Zincke aldehyde cycloaddition approach to indole alkaloids, which permitted the gram-scale synthesis of akuammicine. The chemoselective oxidations of akuammicine leading up to the key rearrangement also generated several biogenetically related alkaloids of the alstolucine and alpneumine families.
- Hong, Allen Y.,Vanderwal, Christopher D.
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p. 7306 - 7309
(2015/06/30)
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- Simple and convenient method for the synthesis of 2-substituted glutaconaldehyde salts and 2-substituted glutaconaldehyde derivatives
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Convenient and scalable syntheses of 2-substituted glutaconaldehyde salts were accomplished from the corresponding pyridinium salts. Glutaconaldehyde salts were additionally converted into aminopentadienal derivatives.
- Nguyen, Tuan Minh,Peixoto, Sabrina,Ouairy, Cecile,Nguyen, Tung Dinh,Benechie, Michel,Marazano, Christian,Michel, Patrick
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experimental part
p. 103 - 109
(2010/04/26)
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- Synthesis of δ-tributylstannyl-α,βγ, δ-unsaturated aldehydes from pyridines
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(Equation Presented) Zincke aldehydes, which are readily available from the ring-opening reaction of pyridinium salts, are easily converted into δ-tributylstannyl-α,β,γ,δ-unsaturated aldehydes (stannyldienals) by the action of tributylstannyllithium. This reaction appears to proceed via 1,6-stannyllithium addition/elimination of lithium dialkylamide. Several stannyldienals of significant utility for the synthesis of polyene natural products have been made by this route, which proceeds in modest yields, but is successful on multigram scale using inexpensive reagents. Simple stannylenals and stannylenones are similarly available from the corresponding vinylogous amides.
- Michels, Theo D.,Rhee, Jong Uk,Vanderwal, Christopher D.
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supporting information; experimental part
p. 4787 - 4790
(2009/05/07)
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- Synthesis of isotopically labelled L-phenylalanine and L-tyrosine
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A synthetic route to stable-isotope-substituted L-phenylalanine is presented, which allows the introduction of 13C, 15N, and deuterium labels at any position or combination of positions. For labelling of the aromatic ring, a synthetic route to ethyl benzoate (or benzonitrile) has been developed, based on the electrocyclic ring-closure of a 1,6-disubstituted hexatriene system, with in situ aromatization by elimination of one (amino) substituent. Several important (highly isotopically enriched) synthons have been prepared, namely benzonitrile, benzaldehyde, ethyl benzoate, and ethyl diphenyloxyacetate. Labelled L-phenylalanines have been synthesized from both aromatic precursors by initial conversion into sodium phenylpyruvate and subsequent transformation of this intermediate into the L-α-amino acid by an enzymatic reductive amination reaction. In this manner, highly enriched phenylalanines are obtained on the 10-gram scale and with high enantiomeric purities (≥ 99% ee). The method has been validated by the synthesis of [1'13C]-L-Phe and [2-D]-L-Phe. In addition, two methods are described for the introduction of isotopes into L-tyrosine starting from the isotopically enriched precursors benzonitrile and ethyl benzoate.
- Raap, Jan,Nieuwenhuis, Saskia,Creemers, Alain,Hexspoor, Sander,Kragl, Udo,Lugtenburg, Johan
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p. 2609 - 2621
(2007/10/03)
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- N.C.A. 11C-labelling of benzenoid compounds in ring positions: Synthesis of nitro-[1-11C]benzene and [1-11C]aniline
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The paper describes the first method for n.c.a. 11C-ring labelling of benzenoid compounds having a reactive group for further derivatization by use of the known principle of synchronous six-electron cyclization of hexatriene systems into aromatics. Nitro-[11C]methane (1) prepared from cyclotron-produced [11C]carbon dioxide reacts in the presence of t-BuOK with 5-dimethylaminopenta-2,4-dienylidene-dimethylammonium perchlorate (2) to form 6-nitro-1-dimethylamino-[6-11C]hexatriene (3) followed by cyclization/aromatization into nitro-[1-11C]benzene (4) at increased temperatures. Starting from 1, nitro-[1-11C]benzene of a radiochemical purity of about 92% and a mean specific radioactivity of 1 Ci/μmol was obtained within 7 min. Related to [11C]CO2, the reproducible radiochemical yield of 4 (decay-corrected) was 80 ± 5%. Reduction of 4 by heating the above reaction mixture with aqueous Na2S gave [1-11C]aniline (5) of a radiochemical purity of about 81%. The reproducible radiochemical yield of 5 (decay-corrected) in relation to [11C]CO2 was 65 ± 5%, the synthesis time from I was 18 min.
- Steinbach,Mading,Fuchtner,Johannsen
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- Attempted Synthesis of Push-Pull Diacetylenes
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Two alternative synthesis of push-pull diacetylenes of type 1 (5-amino-2,4-alkadiynals) are investigated.A bromination-dehydrobromination sequence starting with 5-dimethylamino-2,4-pentadienal (2) as well as application of the well-known Cadiot-Chodkiewicz coupling reaction give intermediates 3-5, and 7 and 8, respectively, but fail to give the target molecules 1.
- Staempfli, Urs,Neuenschwander, Markus
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p. 1427 - 1435
(2007/10/02)
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