Synthesis of polyhydroxylated pyrrolidines from sugar-derived bromonitriles through a cascade addition of allylmagnesium bromide/cyclization/reduction
作者:Michał Malik、Sławomir Jarosz
DOI:10.1039/c5ob02573g
日期:——
in a cascade addition of allylmagnesium bromide/SN2 cyclization/reduction with Zn(BH4)2 is described. The stereochemicalcourse of the reduction step is rationalized. Two of the obtained compounds are transformed into stereoisomers of naturally-occurring iminosugar (+)-lentiginosine. In an alternative approach, 2,2-diallylpyrrolidines are obtained from bromonitriles in a cascade addition of allylmagnesium
The synthesis of novel polyhydroxylated quinolizidines and azaspiro[4.5]decanes is reported. A key step of this transformation involved an addition of allylmagnesium bromide to an ω-bromonitrile derived from d-xylose followed by an intramolecular displacement of a bromide. The resulting cyclic imine was treated either with allylmagnesium bromide or with NaBH4, to provide 2,2-diallyl- or 2-allylpiperidine
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 stereoselectivesynthesis of unnatural (−)-castanospermine. Cyclization of the key intermediate with PhSeBr afforded the desired bicyclic scaffold. In an alternative route, hydroboration/oxidation followed