Resumen de Isolation of Sesamin from Consumer Goods and Investigation of Its Acid-Catalyzed Epimerization: An Introductory Organic Lab Experiment Combining Natural Product Isolation and Spectral Analysis
James A. Ciaccio, Baran Ak, Kareem Hassan
The pharmacologically active lignans sesamin and sesamolin are minor components of sesame oil and ingredients in OTC dietary supplement capsules. We report an introductory undergraduate organic laboratory experiment combining natural product isolation and spectral analysis in which students isolate a mixture of sesamin and sesamolin by either (1) dry column vacuum chromatography (a convenient alternative to flash column chromatography) of commercial sesame oil using an apparatus constructed from common laboratory glassware or by (2) solid–liquid extraction of commercial sesame seed lignan dietary supplement capsules. Two recrystallizations from methanol remove most of the sesamolin to afford crystalline sesamin, which, due to its 2-fold rotational symmetry, students can easily identify and characterize by NMR. During a second laboratory period, students perform a 5 min, test tube-scale reaction of sesamin with catalytic BF3:OEt2 to promote its epimerization to episesamin, a diastereomer of sesamin lacking rotational symmetry, and the sesamin/episesamin ratio in the resulting product mixture is established by 1H NMR integration. Students are asked to propose a mechanism for this epimerization based on their knowledge of the reactivity of benzyl ethers under acidic conditions.
