Biomimetic Organocatalytic Approach to 4-Arylquinolizidine Alkaloids and Application in the Synthesis of (−)-Lasubine II and (+)-Subcosine II
作者:Seerat Virk、Sunil V. Pansare
DOI:10.1021/acs.orglett.9b01840
日期:2019.7.19
An enantioselective, biomimetic organocatalytic synthesis of 4-arylquinolizidin-2-ones, key intermediates in the synthesis of several Lythraceae alkaloids, was developed. The methodology features S-proline-mediated Mannich/aza-Michael reactions of readily available arylideneacetones and Δ1-piperideine. The total syntheses of (−)-lasubine II and (+)-subcosine II as well as the formal syntheses of structurally
Seco-alkaloids 4-7 were treated with VOF3 and VOCl3, under a variety of conditions. No coupled products were detected. However, ring chlorinated and side-chain oxidized products were obtained from the VOCl3 oxidation of 4 and 7 respectively. The generality of the ring chlorination reaction was confirmed by chlorination of simple 0-methoxy phenols under these conditions to yield 17 and 23. In certain