Triphenylphosphine/CCl4-mediated cyclization of amino alcohol 17 proceeded smoothly, with single inversion, to provide (−)-indolizidine 223AB 4. Amino alcohol 17 was prepared by thermolysis of azide 16, followed by DIBAL reduction of the intermediate imine. Symchiral aldehyde 12 and phosphonium salt 15, precursors to 16, were prepared by BINAP·Ru*-mediated hydrogenation of the corresponding β-keto esters. A simplified procedure allows this hydrogenation to be carried out in a Parr shaker, at 80 °C and 50 psig of H2.
All Science Journal Classification (ASJC) codes
- Organic Chemistry