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Stereocontrolled syntheses of (-)-cubebol and (-)-10-epicubebol involving intramolecular cyclopropanation of alpha-lithiated epoxides
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Hodgson, David M., Salik, Saifullah and Fox, David J. (2010) Stereocontrolled syntheses of (-)-cubebol and (-)-10-epicubebol involving intramolecular cyclopropanation of alpha-lithiated epoxides. Journal of Organic Chemistry, Vol.75 (No.7). pp. 2157-2168. doi:10.1021/jo9022974 ISSN 0022-3263.
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Official URL: http://dx.doi.org/10.1021/jo9022974
Abstract
Formylation of (-)-menthone (11) with LDA and HCO2CH2CF3 avoids loss of configurational integrity at the isopropyl group, giving hydroxymethylenementhone 12. Lithium 2,2,6,6-tetramethyl-piperidide-induced intramolecular cyclopropanation of derived unsaturated terminal epoxide 17 (and chlorohydrin 16), efficiently generates a substituted tricyclo[4.4.0.0(1,5)]decan-4-ol 18, which is used in a concise synthesis of (-)-cubebol (1). In contrast, isopropyl group inversion during formylation of menthone with NaOMe and HCO2Et led, by a similar strategy, to syntheses of 7-epicubebol (33) and (from (+)-menthone) of naturally occurring (-)-10-epicubebol (39), confirming the original structural assignment. Computational studies support the origin of the inversion as being rate-determining formylation of cis-enolate 27 from a mixture of rapidly interconverting enolates. In the synthesis of 7-epicubebol (33), allylic tertiary C-H insertion is observed as a significant competing reaction in the intramolecular cyclopropanation of unsaturated terminal epoxide 22.
Item Type: | Journal Article | ||||
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Subjects: | Q Science > QD Chemistry | ||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Chemistry | ||||
Journal or Publication Title: | Journal of Organic Chemistry | ||||
Publisher: | American Chemical Society | ||||
ISSN: | 0022-3263 | ||||
Official Date: | 2 April 2010 | ||||
Dates: |
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Volume: | Vol.75 | ||||
Number: | No.7 | ||||
Number of Pages: | 12 | ||||
Page Range: | pp. 2157-2168 | ||||
DOI: | 10.1021/jo9022974 | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Access rights to Published version: | Restricted or Subscription Access | ||||
Funder: | Higher Education Commission of Pakistan, Engineering and Physical Sciences Research Council (EPSRC) |
Data sourced from Thomson Reuters' Web of Knowledge
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