- Short synthesis of polyoxygenated macrocyclic rings using acetal linkages. Application to the preparation of a new lipidic polyamine
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A short preparation of polyoxygenated macrocycles can be carried out by combining the formation of an acetal linkage, to introduce long alkyl chains, with a ring closure metathesis. As an example, this methodology was used to synthesize a new polyamino li
- Miramon, Marie-Laure,Mignet, Nathalie,Herscovici, Jean
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p. 6949 - 6952
(2007/10/03)
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- Studies on intramolecular alkylation of an α-sulfinyl vinylic carbanion: A novel route to chiral 1-cycloalkenyl sulfoxides
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Intramolecular alkylation of various β-(ω-haloalkyl) substituted vinylic sulfoxides was investigated. Upon treatment with LDA in THF at -78°C, α-sulfinyl carbanion generated from vinylic sulfoxides cyclized at the α-sulfinyl position to give 1-cycloalkenyl sulfoxides with a five- to seven-membered ring. Although iodide or bromide is normally a good leaving group, chloride affords better results than the corresponding iodide and bromide when the reaction takes place at the benzylic position. The cyclization proceeded even with the secondary iodide in moderate yield. Not only the (E)-isomer but also the (Z)-isomer cyclized via rapid inversion of the olefin geometry. No loss of optical purity was observed during isomerization. Various 1-cycloalkenyl sulfoxides including a fused ring and a polyoxygenated rings were synthesized in good to moderate yields. (C) 2000 Elsevier Science Ltd.
- Maezaki, Naoyoshi,Izumi, Mayuko,Yuyama, Sachiko,Sawamoto, Hiroaki,Iwata, Chuzo,Tanaka, Tetsuaki
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p. 7927 - 7945
(2007/10/03)
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- Selective monotetrahydropyranylation of symmetrical diols catalyzed by ion-exchange resins
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Primary and secondary symmetrical diols with 2-10 carbon atoms gave selectively monotetrahydropyranyl ethers in the reaction catalyzed by wet sulfonic acid-type ion-exchange resins in 3,4-dihydro-2H-pyran (DHP)/toluene or DHP/hexane. The yields of the monoethers were higher than 80% while those of the corresponding diethers were lower than 5%. In these reactions the rate of the formation of the diethers did not increase much even after most of the diols had been consumed. In the reaction of 1,10-decanediol in DHP/hexane, the yields of the monoether were increased by the addition of DMF or DMSO. Each diol was found to have a particular DHP/hydrocarbon ratio that gave the highest selectivity for the monoether. Generally, the larger the number of carbon atoms of the diols, the smaller the ratio of DHP in the solvents to give high selectivity for the monoether. This method of the selective etherification is quite simple and practical.
- Nishiguchi, Takeshi,Fujisaki, Shizuo,Kuroda, Masahumi,Kajisaki, Kohtaro,Saitoh, Masahiko
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p. 8183 - 8187
(2007/10/03)
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