New Building Blocks for Fluorinated Bioimidazole Derivatives II: Preparation of β-Fluorourocanic Acids
作者:Bohumil Dolensky、Kenneth L. Kirk
DOI:10.1021/jo0200419
日期:2002.5.1
Replacement of vinyl hydrogen with fluorine is based on addition of an FBr equivalent to a double bond followed by HBr elimination. This sequence has been adapted to prepare 3-fluoro-3-imidazolyl-propenoic acids (beta-fluorourocanic acids), and the related fluorinated imidazolyl propenals and prop-2-en-1-ols, from urocanic acid. Tritylation of the imidazole nitrogen was necessary for successful addition of "FBr" to the double bond, and prior reduction of the carboxyl group to the alcohol was required to provide the desired chemoselectivity in the elimination of HX. Reoxidation and deprotection produced the fluorinated urocanic acids.
New approaches to side-chain fluorinated bioimidazoles: 4-alkynylimidazoles as substrates for fluorination
作者:Bohumil Dolensky、Kenneth L Kirk
DOI:10.1016/s0022-1139(03)00197-0
日期:2003.11
3b met with failure. Reduction of the ester gave the hydroxymethyl-substituted acetylene 4. Addition of “FBr” to this substrate and reductive removal of bromine from the product produced fluoroolefins 12, precursors to E- and Z-β-fluorourocanic acids. The same fluoroolefins can be used as intermediates in the synthesis of β-fluorohistidinols.