- Enantiocontrolled total syntheses of breviones A, B, and C
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Enantiocontrolled total syntheses of the breviones A, B, and C have been accomplished using a highly diastereoselective oxidative coupling of an α-pyrone with a tricyclic diene prepared from an optically pure Wieland-Miescher ketone derivative through the 7-endo-trig mode of acyl radical cyclization.
- Yokoe, Hiromasa,Mitsuhashi, Chika,Matsuoka, Yoko,Yoshimura, Tomoyuki,Yoshida, Masahiro,Shishido, Kozo
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- Enantioselective total synthesis of (-)-candelalides A, B and C: Potential Kvl.3 blocking immunosuppressive agents
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Novel Kv1.3 blocking immunosuppressants, (-)-candelalides A, B and C, were efficiently synthesized for the first time in a convergent and unified manner starting from (+)-5-methyl-Wieland-Miescher ketone. The synthetic method involved the following key steps: i) a strategic [2,3]-Wittig rearrangement of a stannylmethyl ether to install the stereogenic center at C9 and the exo-methylene function at C8 present in the decalin portion; ii) a straightforward coupling of a transdecalin portion (BC ring) and a γ-pyrone moiety through the C16-C3′ bond to assemble the requisite carbon framework; and iii) a construction of a characteristic di or tetrahydropyran ring (A ring) by internal nucleophilic ring closure of a hydroxy aldehyde or a hydroxy epoxide. The present total synthesis has fully established the absolute configuration of these natural products.
- Oguchi, Takamasa,Watanabe, Kazuhiro,Ohkubo, Koichi,Abe, Hideki,Katoh, Tadashi
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- Total synthesis of Herbarin A and B, determination of their antioxidant properties and toxicity in zebrafish embryo model
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Herbarin A and B were isolated from the fungal strains of Cladosporium herbarum found in marine sponges Aplysina aerophoba and Callyspongia aerizusa. Total synthesis of Herbarin A and B was achieved by carrying out a multi-step synthesis approach, and the antioxidant properties were evaluated using FRAP assay. Toxicity of these compounds was determined using a zebrafish embryo model.
- Heimberger, Julia,Cade, Hannah C.,Padgett, Jihan,Sittaramane, Vinoth,Shaikh, Abid
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- Regioselective functionalization of pyrones: Facile synthesis of 6-styrylpyrones via KHMDS-mediated aldol condensation
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Herein, we disclose our efforts directed toward the synthesis of the kavalactone-based natural product penstyrylpyrone and other related 4-OMe-2-pyrones possessing diverse substituents at the 3-, 5-, and 7-positions. Further, a facile approach to access 6-styrylpyrones via the KHMDS-mediated regioselective aldol condensation of 2-pyrones is described with moderate substrate scope and good to high yields (58–80%). The utility of this methodology was exemplified by the stereoselective construction of desmethoxyyangonin, asnipyrone A, and asnipyrone B.
- Basu, Manas K.,Mukkanti, K.,Samala, Ramakrishna
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- Expanding the structural diversity of polyketides by exploring the cofactor tolerance of an inline methyltransferase domain
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A strategy for introducing structural diversity into polyketides by exploiting the promiscuity of an in-line methyltransferase domain in a multidomain polyketide synthase is reported. In vitro investigations using the highly-reducing fungal polyketide synthase CazF revealed that its methyltransferase domain accepts the nonnatural cofactor propargylic Se-adenosyl-l-methionine and can transfer the propargyl moiety onto its growing polyketide chain. This propargylated polyketide product can then be further chain-extended and cyclized to form propargyl-α pyrone or be processed fully into the alkyne-containing 4′-propargyl-chaetoviridin A.
- Winter, Jaclyn M.,Chiou, Grace,Bothwell, Ian R.,Xu, Wei,Garg, Neil K.,Luo, Minkui,Tang, Yi
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supporting information
p. 3774 - 3777
(2013/08/23)
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- Synthesis of methylenebis(4-hydroxy-2-pyrone) or methylenebis(4- hydroxycoumarin) derivatives by organic solid state reaction
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Methylenebis(4-hydroxy-2-pyrone) or methylenebis(4-hydroxycoumarin) derivatives (5) have been synthesized from 4-hydroxy-2-pyrones or 4- hydroxycoumarin (3) with aldehydes (4) by organic solid state reaction.
- Hagiwara, Hisahiro,Fujimoto, Norikazu,Suzuki, Toshio,Ando, Masayoshi
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p. 549 - 552
(2007/10/03)
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- An Improved Method for γ-Carboxylation of β-Diketones. Synthesis of 4-Alkyl-3,5-dioxohexanoic Acids and 5-Alkyl Derivatives of Triacetic Acid Lactone
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γ-Carboxylation of β-diketones, 1, can be improved using samples containing 100percent of ketoenol tautomers, 3, prepared by mild hydrolysis of the corresponding copper(II) complexes 2.Cyclization of the so formed 4-alkyl-3,5-dioxohexanoic acids, 4, affords 5-alkyl-4-hydroxy-6-methyl-2-pyrones, 5.
- Cervello, Jordi,Marquet, Jorge,Moreno-Manas, Marcial
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p. 1931 - 1941
(2007/10/02)
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- Total synthesis of (±)-asteltoxin
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A convergent synthesis of (±)-asteltoxin has been achieved in 16 steps (3.0% overall yield) from 3,4-dimethylfuran. The attachment of the triene pyrone side chain to the bis(tetrahydrofuran) skeleton proceeds by way of the addition of the Corey equivalent to anion 3 to the aldehyde 2 and a subsequent aldol condensation-dehydration reaction of pyrone 4.
- Schreiber,Satake
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p. 4186 - 4188
(2007/12/18)
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- Convenient Syntheses of Alkyl β-Resorcylate Derivatives
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Syntheses of methyl 2,4-dihydroxy-6-methyl- (1a) and -3,6-dimethylbenzoates (1b) and methyl 2,4-dihydroxy-6-pentylbenzoate (1c) are described.Condensation reactions of dimethyl sodiomalonate with the dianion derived from pentane-2,4-dione or the dimerisation of the methyl acetoacetate dianion or the acetylation of the trianion derived from methyl 3,5,7-trioxo-octanoate gave (1a) (78percent) after work-up at pH 9.Analogous convenient, short, optimised syntheses of (1b and c) are given in detail.
- Barrett, Anthony G. M.,Morris, Timothy M.,Barton, Derek H. R.
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p. 2272 - 2277
(2007/10/02)
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