Approach to the Homoerythrina Alkaloids Using a Tandem N-Alkylation/Azomethine Ylide Cycloaddition
journal contributionposted on 25.05.2007 by William H. Pearson, Jeffrey E. Kropf, Allison L. Choy, Ill Young Lee, Jeff W. Kampf
Any type of content formally published in an academic journal, usually following a peer-review process.
Synthetic efforts toward the homoerythrina alkaloids 1−3 are described. Two separate model systems guided the pivotal [3 + 2] azomethine ylide cycloaddition cascade to form the A−C rings of these alkaloids. The cycloaddition precursors 63 and 68, prepared in nine and ten steps, respectively, from alkyne 47, each contain an enolizable ketone, a tethered electrophile, and an electron-poor dipolarophile. Heating 63 and 68 with the stannyl amine 17 generated demethoxyschelhammeridine 65 and demethoxyschelhammericine 70, the products of intramolecular azomethine ylide cycloadditions. Subsequent attempts to install the C-3 methoxy group of 1−3 are also described.