Stereoselective Synthesis of syn‐β‐Amino Propargylic Ethers: Application to the Asymmetric Syntheses of (+)‐β‐Conhydrine and (−)‐Balanol

The stereoselective synthesis of syn‐β‐amino propargylic ethers by the addition of racemic lithio 3‐(methoxymethoxy)allenylcuprates, and more particularly (cyano) and (mesityl)cuprates, to enantiopure chiral N‐tert‐butylsulfinylimines is reported. The scope and limitations of the reaction is studied. The usefulness of the methodology for the synthesis of compounds having a syn‐1,2‐amino alcohol unit is shown through the development of the asymmetric syntheses of (+)‐β‐conhydrine and of an advanced intermediate of (−)‐balanol.