Synthesis of (−)-β conhydrine and analogues using N-Boc-2-acyl oxazolidine methodology and ring closing metathesis

Two key-steps involving: (i) a stereoselective reduction of an N-Boc-2-acyl oxazolidine; and (ii) an RCM performed on enantiopure trans-3,4,5-trisubstituted oxazolidin-2-ones account for the synthesis of unsaturated bicyclic oxazolidin-2-ones with various sizes of ring. One of these bicyclic compounds was transformed into (−)-β-conhydrin. An unsaturated and a dihydroxylated analogue of this alcaloid were also prepared from the same starting material.