Progress in the Total Synthesis of Several Goji Berry-Pyrrole Alkaloids
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Date
2016-05
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The Ohio State University
Abstract
Goji berries, the fruits of Lycium barbarum L. (Solanaceae), have become increasingly popular in the U.S. as a “super fruit” and botanical dietary supplement. Goji berry extracts have demonstrated numerous biological effects including immunomodulatory, anti-aging, and anti-cancer activities. Several amino acid-containing pyrrole alkaloids isolated from these extracts have shown potency in a quinone reductase induction assay, suggesting potential chemopreventive activity. These isolates possess similar structures, but it remains unclear what causes one to be more active than another. While it is known that each compound contains a chiral center, it is unknown what the configuration of each is. The purpose of this project was to investigate potential synthetic schemes that can be used for the total synthesis of each of the five isolated pyrrole alkaloids. The total synthesis of these compounds will allow for the determination of the stereochemical descriptors for each isolated molecule. This synthesis will be performed through the Paal-Knorr pyrrole synthesis method, which combines a saturated 1,4-diketo compound and a primary amine to form a pyrrole. The synthesized compounds will have a known stereochemistry and by comparing their optical rotation and circular dichroism with those obtained for the isolated compounds, the stereochemical descriptors can be determined. Additionally, this synthetic method will enable the interrogation of the structure activity relationship of these compounds by synthesizing both their R and S isomers, as well as novel pyrroles using additional amino acids. Several synthetic schemes have been tested in attempts to synthesize the desired pyrroles. Further studies are also being conducted which involve the use of the Maillard Reaction instead of the Paal-Knorr Pyrrole Synthesis as a method for forming the isolated pyrrole alkaloids.
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Keywords
Synthesis, Natural Products, Goji, Pyrrole