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Download fileCarboxybenzyl Group as an O‑Nucleophile in the C–H Allylic Oxidation: Total Synthesis of (−)-Castanospermine
journal contribution
posted on 18.07.2014, 00:00 authored by Michał Malik, Grzegorz Witkowski, Sławomir JaroszThe
first palladium-mediated C–H allylic oxidation with
a Cbz group acting as an O-nucleophile is reported.
It was found that this transformation is promoted by rare-earth metal
triflates: Yb(OTf)3 or Sc(OTf)3. A possible
catalytic cycle is proposed. This reaction was applied in the synthesis
of a d-xylose derived oxazolidinon, a versatile intermediate
used further in the stereoselective synthesis of unnatural (−)-castanospermine.
Cyclization of the key intermediate with PhSeBr afforded the desired
bicyclic scaffold. In an alternative route, hydroboration/oxidation
followed by DPPA-mediated cyclization was used.