- An improved and novel approach to macrolactonisation using di-tert-butyl dicarbonate
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A new, facile, mild and simple method for the synthesis of macrolides was achieved from ω- hydroxy acids using di-tertbutyl dicarbonate (Boc2O), a cheap and commercially available reagent. A wide range of substrates were tested and give good yield of lactones. The effect of various simple bases on the yield of the macrolactonisation reaction was also studied.
- Nagarajan,Satish Kumar,Venkateswara Rao
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- Macrocyclisation of macrodiolide with dimethylaluminium methaneselenolate
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Dimethylaluminium methaneselenolate (Me2AlSeMe, 1) acts as an acyl transfer agent for esterification. In cases of direct macrolactonisation (n = 10-12), this selenium-aluminium complex preferentially creates symmetric macrodiolides rather than macrolides. The factors determining macrodilactonisation were investigated and applied toward the total synthesis of norpyrenophorin, which result in a macrodilactonisation yield of 64 %. Dimethylaluminium methaneselenolate (Me2AlSeMe, 1) acts as an acyl transferagent for esterification. In cases of direct macrolactonisation (n = 10-12), this selenium-aluminium complex preferentiallycreates symmetric macrodiolides rather than macrolides. The factors determining macrodilactonisation were investigated and applied toward the total synthesis of nor-pyrenophorine. Copyright
- Shen, Liu-Lan,Mun, Han-Seo,Jeong, Jin-Hyun
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scheme or table
p. 6895 - 6899
(2011/02/24)
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- A new method for the lactonization of ω-hydroxy carboxylic acids with Di-2-thienyl carbonate by the promotion of DMAP and iodine
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Successive reactions of ω-hydroxycarboxylic acids with an equimolar amount of di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino)pyridine (DMAP) followed by an addition of 2-4 equimolar amounts of iodine afforded the corresponding lactones in good to high yields. Copyright
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
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- Efficient method for the lactonization of ω-hydroxycarboxylic acids with di-2-thienyl carbonate by the promotion of catalytic amounts of DMAP and Hf(OTf)4
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An efficient method for the synthesis of macrolides from ω-hydroxycarboxylic acids is established by using an equimolar amount of di-2-thienyl carbonate (2-DTC) and catalytic amounts of 4-(dimethylamino) pyridine (DMAP) and group 4 metal triflates such as hafnium(IV) trifluoromethanesulfonate (Hf(OTf)4). Copyright
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
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p. 710 - 711
(2007/10/03)
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- A new method for the synthesis of carboxylic esters and lactones with di-2-thienyl carbonate (2-DTC) by the promotion of DMAP and iodine
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The esterification of carboxylic acids with alcohols by using di-2-thienyl carbonate (2-DTC) in the presence of a catalytic amount of 4-(dimethylamino) pyridine (DMAP) proceeded smoothly to afford the corresponding esters in good-to-high yields along with 2(5H)-thiophenone. This esterification was accelerated by the addition of an equimolar amount of iodine to afford the esters in higher yields within a shorter reaction time. Further, cyclization of ω-hydroxycarboxylic acids with an equimolar amount of 2-DTC in the presence of a catalytic amount of DMAP, followed by the addition of 1-4 equimolar amounts of iodine, afforded the corresponding lactones in good-to-high yields under mild conditions. This method was successfully employed in the synthesis of erythro-aleuritic acid lactone.
- Oohashi, Yoshiaki,Fukumoto, Kentarou,Mukaiyama, Teruaki
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p. 1508 - 1519
(2007/10/03)
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- A new method for the polymer-supported synthesis of cyclic oligoesters for potential applications in macrocyclic lactone synthesis and combinatorial chemistry
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Attachment of ω-hydroxyalkanecarboxylic acids to Merrifield beads followed by treatment with a catalytic amount of di-n-butyltin oxide in chlorobenzene at 133 °C for 4-18 h brought about the formation of the corresponding cyclic oligomers (COs) as the mai
- Ruddick, Clare L.,Hodge, Philip,Cook, Anthony,McRiner, Andrew J.
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p. 629 - 637
(2007/10/03)
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- New and efficient method for the preparation of medium-sized lactones from the corresponding ω-hydroxycarboxylic acids
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Medium-sized lactones are prepared in good yields on treating monomeric cyclic silyl siloxycarboxylates, prepared in situ from ω-hydroxycarboxylic acids and 1,2-bisdimethylsilylbenzene using RhCl(PPh3)3 catalyst, with an active catalyst of dimethylsilylbis(trifluoromethanesulfonate).
- Mukaiyama, Teruaki,Izumi, Jun,Shiina, Isamu
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p. 187 - 188
(2007/10/03)
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- Scandium trifluoromethanesulfonate as an extremely active Lewis acid catalyst in acylation of alcohols with acid anhydrides and mixed anhydrides
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Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis acid catalyst for acylation of alcohols with acid anhydrides or the esterification of alcohols by carboxylic acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of ω-hydroxy carboxylic acids.
- Ishihara, Kazuaki,Kubota, Manabu,Kurihara, Hideki,Yamamoto, Hisashi
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p. 4560 - 4567
(2007/10/03)
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- A New Synthetic Method of Macrocyclic Lactones from ω-Iodoalkylacrylates
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When the photostimulated cyclization reaction of ω-iodoalkylacrylates was performed in the presence of metal hydride complexes such as sodium cyanoborohydride (NaBH3CN), sodium borohydride (NaBH4) and potassium borohydride (KBH4), the corresponding macrocyclic lactones were produced.The use of NaBH3CN led to the highest yield of lactones.
- Abe, Motoji,Hayashikoshi, Takaoki,Kurata, Takeo
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p. 1789 - 1792
(2007/10/02)
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- A Novel Method for the Preparation of Macrolides from ω-Hydroxycarboxylic Acids
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An efficient method for the synthesis of macrolides directly from ω-hydroxycarboxylic acids is established by using 4-(trifluoromethyl)benzoic anhydride and a catalytic amount of active titanium(IV) salts together with chlorotrimethylsilane under mild conditions.
- Shiina, Isamu,Mukaiyama, Teruaki
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p. 677 - 680
(2007/10/02)
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- Intramolecular Cyclization of (ω-Carboxyalkyl)sulfonium Salts. A Novel Synthesis of Macrocyclic Lactones
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A useful method for the synthesis of macrocyclic lactones using (ω-carboxyalkyl)sulfonium salts was developed.Base-catalyzed intramolecular cyclization of (ω-carboxyalkyl)diphenylsulfonium salts 2 gave simple macrocyclic lactones in high yields at high dilution conditions. (ω-Carboxyalkyl)alkylphenylsulfonium salts 8 afforded simple macrocyclic lactone 6a and alkyl carboxylates 9.The reactions of (ω-carboxyalkyl)dialkylsulfonium salts 10 gave only esters without lactonization product 6a.The cyclization of S-(ω-carboxyalkyl)thiolanium salts 3 and S-(ω-carboxyalkyl)-2-methylthiolanium salts 4 took place readily under similar conditions to afford sulfur-containing macrocyclic lactones 13 and 15, respectively, in good yields.To investigate the reaction mechanism, sulfonium salt 25, having an optically active carbon atom, was prepared.The intramolecular cyclization of 25 took place with an inversion of configuration at chiral carbon atom to give ricinelaidic acid lactone (26; optical purity 66percent).
- Matsuyama, Haruo,Nakamura, Takako,Kamigata, Nobumasa
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p. 5218 - 5223
(2007/10/02)
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- Preparation of Macrocyclic Lactones by Ring Closure of Cesium Carboxylates
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A series of ω-halo fatty acids, the longest being 16-iodohexadecanoic acid, was prepared by oxidation of the corresponding ketones with m-chloroperbenzoic acid in boiling chloroform, followed by ring opening usually with hydrogen iodide in acetic acid at 100 deg C.Solutions of these acids in dimethylformamide (DMF) at concentrations of 5E-3 - 5E-2 M were treated with an equivalent amount of dry Cs2CO3.The solutions were stirred at 40 deg C overnight.Workup of the reaction mixture produced a mixture of (macro)cyclic lactone (macrolide) and its dimer (dilide).For the case of 16-iodohexanoic acid the lactone was isolated in 85percent yield.Yields for other large ring macrolides were also excellent.It was demonstrated that substitution by carboxylate on a secondary halide also goes well to afford the corresponding macrolide with no detectable amount of elimination.The effects of ring size, concentration, and solvent on the ring closure of the cesium carboxylates formed in situ were investigated.DMF is the best solvent of those investigated for the ring closure.Cesium carboxylates also undergo more readily ring closure and in far better yield than the carboxylates of lithium, sodium, potassium, rubidium, silver, thallium, magnesium, strontium, or barium.The S-lactone of ricinelaidic acid was prepared optically pure in 80percent yield from optically pure mesylate of R-ricinelaidic acid, which was treated with cesium carbonate in dry DMF.This demonstrates that the ring closure proceeds with the anticipated SN2 inversion at the hydroxyl-bearing carbon atom.With the same approach optically pure S-zearalenone was protected and subjected to ring opening, and the hydroxyl group was activated as mesylate.Some racemization was found to occur in the ring-opening step.On treatment of this material with dry cesium carbonate in DMF, the desired ring closure took place in 80percent yield to provide an excess of the protected R enantiomer of zearalenone.On the basis of these results, some speculations are made concerning the action of cesium in promoting ring closure to macrocyclic lactones.
- Kruizinga, Wim H.,Kellogg, Richard M.
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p. 5183 - 5189
(2007/10/02)
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