A convergent and modular synthesis of dienyl and diynyl isobutylamide natural products from Echinacea and Spilanthes herbal medicines.

摘要

"Echinacea" and "Spilanthes" are popular over-the-counter herbal supplements derived from raw tissue or tissue extracts from plants such as Echinacea purpurea and Spilanthes acmella, respectively. Several chemical constituents have been identified as possible candidates for these plants' supposed medicinal activities, and include the "alkylamides," of which dienyl and diynyl analogs are prominent members. Isolation of these compounds from the plants is often difficult and results in poor yields. The goal of our research was to develop an encompassing synthesis scheme for dienyl and diynyl alkylamides (Figure 1) addressing consistent functional groups, using a Wittig reaction, a Horner-Wadsworth-Emmons reaction and a Sonogashira reaction. The total syntheses for these compounds have been reported, but are rather lengthy procedures. We have developed a novel synthesis for a Spilanthol derivative which involves only three reactions and based on the Sonogashira coupling reaction for introduction of the diynyl structure.*; *Please refer to dissertation for diagrams.