期刊
TETRAHEDRON
卷 68, 期 52, 页码 10806-10817出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2011.11.007
关键词
2-Azetidinones; Monolactams; Kinugasa reaction; Asymmetric synthesis; Assignment of absolute configuration; Circular dichroisms
资金
- Polish Ministry of Science and Higher Education [N N204 156036]
The methodology of construction of N,4-diaryl substituted beta-lactam framework, based on the Kinugasa cycloaddition/rearrangement sequence is presented. The series of protected chiral propargyl alcohols was treated with diaryl nitrones to afford mainly the cis-I adduct, providing direct access to the highly-functionalized azetitidin-2-one derivatives with a well-defined stereochemistry. Under the optimized reaction conditions, the unprotected chiral propargylic alcohols were also found to be suitable precursors of beta-lactams. The absolute configuration of adducts was determined by CD or HPLC-CD technique, which was shown to be reliable method of determination of the configuration at C-4 of 4-aryl-substituted azetidin-2-ones. Epimerization of the cis adduct to the respective trans isomer could be easily done by the oxidation of hydroxyl group next to the four-membered beta-lactam ring to the ketone, followed by a base-mediated epimerization of the malonyl fragment. (C) 2011 Elsevier Ltd. All rights reserved.
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