Alternative Synthesis of P‑Chiral Phosphonite-Borane Complexes: Application to the Synthesis of Phostone–Phostone Dimers

An improved strategy for the synthesis
of P-chiral gluco- and manno-phosphonite-borane
complexes is described on the basis of the addition of diethyl phosphonite-borane
to a glucal-derived aldehyde, followed by a cyclization coupled with
an ethyl/methyl exchange. This direct P­(III) strategy facilitates
the obtention of various P-chiral phosphonite-boranes, of which further
coupling reactions are described leading to the selective synthesis
of two phostone dimers.