Preparation of Hexahydrolupulone Derivatives
Schultz, Robert L.
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Hops have been used in the production of beer since the Bavarian Purity Law of 1516. They were primarily used for the bitter flavor to dilute the sugars from malted barley, but early brewers found the flowers also preserved the beverage over long journeys or the winter months. Using spectroscopic techniques and studies on different types of bacteria have identified β-acids, or lupulones, as the antiseptic component of hops. This small family of essential oils is effective against Gram-positive bacteria like Staphlococcus aureus and Bacillus cereus. With the increasing concerns of drug-resistant bacteria, new alternatives have been investigated like lupulones. Studies in this group of compounds have formed a new reduced form of β-acids called hexahydrolupulones (HHL), which are more potent against these bacteria and more stable against photooxidative processes than β-acids. Water solubility has been a drawback in using these compounds as an ingestible antibacterial drug. This report investigates the reactivity of HHL to form esters with benzoic acid derivatives using thionyl chloride and oxalyl chloride. Using this reactivity information can lead to the formation more water-soluble esters of HHL in order to make a more effective antibacterial drug. The products were characterized by 1H NMR and infrared spectroscopy to identify the successfully synthesized esters.