Synthesis of a P-Glycoprotein Inhibitor and Its High-Energy (Z)-Isomer by Carbenoid Eliminative Cross-Coupling
Subhash D Tanpure1, Mohamed F El-Mansy1, Paul R Blakemore1
1Department of Chemistry, Oregon State University, Corvallis, Oregon 97331-4003, United States.
Abstract:
To gauge the feasibility of carbenoid eliminative cross-coupling for the synthesis of polyfunctional alkenes, a P-glycoprotein inhibitor containing an (E)-configured 4-chromanylidene-type trisubstituted olefin was prepared as well as its previously undescribed (Z)-isomer. Stereospecific alkene synthesis required generation of functionalized enantioenriched α-metalated carbamates [R1R2CM(O2CNi-Pr2), M = Li or Bneo], and problems associated with incorrect lithiation regioselectivity and unexpected organolithium configurational lability were encountered. Solutions to these difficulties are described together with a method for ee determination of α-carbamoyloxyboronates.
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