- Catalytic asymmetric intramolecular homologation of ketones with α-diazoesters: Synthesis of cyclic α-Aryl/Alkyl β-ketoesters
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A catalytic asymmetric intramolecular homologation of simple ketones with α-diazoesters was firstly accomplished with a chiral N,N′-dioxide-Sc(OTf)3 complex. This method provides an efficient access to chiral cyclic α-aryl/alkyl β-ketoesters containing an all-carbon quaternary stereocenter. Under mild conditions, a variety of aryl- and alkyl-substituted ketone groups reacted with α-diazoester groups smoothly through an intramolecular addition/rearrangement process, producing the β-ketoesters in high yield and enantiomeric excess.
- Li, Wei,Tan, Fei,Hao, Xiaoyu,Wang, Gang,Tang, Yu,Liu, Xiaohua,Lin, Lili,Feng, Xiaoming
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supporting information
p. 1608 - 1611
(2015/01/30)
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- Total syntheses of neuroprotective mastigophorenes A and B
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(-)-Herbertenediol (3) which is regarded as a biosynthetic precursor of mastigophorenes A and B has been effectively synthesized from (R)-1,2-dimethyl-2-cyclopentene carboxylic acid by applying an intramolecular Heck reaction to the construction of the quaternary carbon center, and then horseradish peroxidase-catalyzed oxidative coupling of 3 has given rise to (-)-mastigophorenes A and B. Mastigophorenes A and B have been found to exhibit significant neuroprotective activity in primary cultures of fetal rat cortical neurons.
- Fukuyama, Yoshiyasu,Matsumoto, Keiji,Tonoi, Yasutoshi,Yokoyama, Ritsuko,Takahashi, Hironobu,Minami, Hiroyuki,Okazaki, Hiroshi,Mitsumoto, Yasuhide
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p. 7127 - 7135
(2007/10/03)
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- Chiral Synthesis via Organoboranes. 42. Selective Reductions. 57. Efficient Kinetic Resolution of Representative α-Tertiary Ketones with B-Chlorodiisopinocampheylborane
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Kinetic resolution of racemic α-tertiary ketones with 0.5-0.6 molar equiv of B-chlorodiisopinocampheylborane provides the product alcohols in very high diastereomeric and enantiomeric excess, with the unreacted ketone recovered in very high ee.For example, ethyl 1-methyl-2-oxocyclopentane- and cyclohexanecarboxylates are partially reduced to recover the ketone in 91 to >/=99percent ee and the product alcohols in up to 94percent de, with >90percent ee for the major diastereomer.Bicyclic ketones, such as 1-methyl- and 1-ethylnorcamphor, camphor, and camphenilone, are readily resolved to provide the ketone in 92 to >/=99percent ee, with the product alcohol recovered in high de and ee.Dihydrospirooctane-2,2'(3'H)-furan>-3-one is resolved to provide the ketone in >/=99percent ee and the product alcohol in >/=99percent de.In all the cases studied, the R-isomer of the ketone is recovered when dIpc2BCl is used for kinetic resolution, while lIpc2BCl provides the S-ketone.Optimum conditions for obtaining the product alcohol, or the ketone, or both, in very high yields and ee have been established.
- Ramachandran, P. Veeraraghavan,Chen, Guang-Ming,Brown, Herbert C.
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- Total synthesis of herbertenediol, an isocuparane sesquiterpene isolated from liverworts
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Total synthesis of herbertenediol, an isocuparane-sesquiterpene possessing a potent anti-lipid peroxidation activity isolated from a liverwort, has been achieved via herbertenol using intramolecular Heck reaction as the key step.
- Fukuyama, Yoshiyasu,Kiriyama, Yuuko,Kodama, Mitsuaki
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p. 1261 - 1264
(2007/10/03)
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- Asymmetric Alkylation Using Chiral Cyclic Diols to Prepare a Quaternary Carbon
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Asymmetric alkylation of cyclic and acyclic β-keto ester acetals (4, 5, 13, 14, and 18) with C2-symmetric cycloalkane-1,2-dioxy moiety proceeded in a highly diastereoselective manner to afford enol ethers (9-12, 15-17, 19a-c) with a chiral quat
- Kato, Keisuke,Suemune, Hiroshi,Sakai, Kiyoshi
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p. 3315 - 3326
(2007/10/02)
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- Asymmetric Syntheses of (-)-Malyngolide and (-)-Frontalin by Utilizing Bakers' Yeast Reduction of S-Ethyl 2-Cyclopentanonecarboxylthioate
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Bakers' yeast reduction of S-ethyl 2-cyclopentanonecarboxylthioate affords optically pure S-ethyl (1R,2S)-2-hydroxycyclopentanecarboxylthioate which is stereoselectively converted into (-)-malyngolide and (-)-frontalin.
- Sato, Toshio,Maeno, Hajime,Noro, Tomohiro,Fujisawa, Tamotsu
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p. 1739 - 1742
(2007/10/02)
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