Continuous-Flow Photochemical Isomerization of Humulones to Isohumulones

Humulones are a family of homolog natural products obtained from the strobiles of humulus lupulus, or hops plants. Structurally, they consist of substituted phloroglucinols with two isoprenyl side chains, a carbonyl group and a quaternary ring carbon substituted with a hydroxyl group. The three most...

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Main Authors: Bruce C. Hamper, Bradley Gallow, Gregory Giovine, Trevor Smith
Format: Article
Language:English
Published: MDPI AG 2025-02-01
Series:Molecules
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Online Access:https://www.mdpi.com/1420-3049/30/5/1002
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author Bruce C. Hamper
Bradley Gallow
Gregory Giovine
Trevor Smith
author_facet Bruce C. Hamper
Bradley Gallow
Gregory Giovine
Trevor Smith
author_sort Bruce C. Hamper
collection DOAJ
description Humulones are a family of homolog natural products obtained from the strobiles of humulus lupulus, or hops plants. Structurally, they consist of substituted phloroglucinols with two isoprenyl side chains, a carbonyl group and a quaternary ring carbon substituted with a hydroxyl group. The three most prominent homologs are n-, co- and ad-humulone, containing isobutyl, isopropyl and secbutyl ketone groups, respectively. When solutions of humulones are exposed to UV light, they undergo stereoselective isomerization to the five-membered ring trans-isohumulones. A photoreactor was assembled from strip LEDs in close contact with UV-transparent tubing. This reactor allowed continuous-flow chemical synthesis of the isohumulones. The yield, conversion and product throughput are compared for the humulones, using LEDs emitting white, blue and ultraviolet light (visible, 400 nm, and 365 nm, respectively). Using an optimized continuous-flow reactor, a throughput of 0.43 g/h was obtained for trans-n-isohumulone.
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spelling doaj-art-e4b542577a6f47c7b9e8ff0ca0c793542025-08-20T02:53:22ZengMDPI AGMolecules1420-30492025-02-01305100210.3390/molecules30051002Continuous-Flow Photochemical Isomerization of Humulones to IsohumulonesBruce C. Hamper0Bradley Gallow1Gregory Giovine2Trevor Smith3Department of Chemistry & Biochemistry, University of Missouri-St. Louis, 43 Benton Ct., St. Louis, MO 63121, USADepartment of Chemistry & Biochemistry, University of Missouri-St. Louis, 43 Benton Ct., St. Louis, MO 63121, USADepartment of Chemistry & Biochemistry, University of Missouri-St. Louis, 43 Benton Ct., St. Louis, MO 63121, USADepartment of Chemistry & Biochemistry, University of Missouri-St. Louis, 43 Benton Ct., St. Louis, MO 63121, USAHumulones are a family of homolog natural products obtained from the strobiles of humulus lupulus, or hops plants. Structurally, they consist of substituted phloroglucinols with two isoprenyl side chains, a carbonyl group and a quaternary ring carbon substituted with a hydroxyl group. The three most prominent homologs are n-, co- and ad-humulone, containing isobutyl, isopropyl and secbutyl ketone groups, respectively. When solutions of humulones are exposed to UV light, they undergo stereoselective isomerization to the five-membered ring trans-isohumulones. A photoreactor was assembled from strip LEDs in close contact with UV-transparent tubing. This reactor allowed continuous-flow chemical synthesis of the isohumulones. The yield, conversion and product throughput are compared for the humulones, using LEDs emitting white, blue and ultraviolet light (visible, 400 nm, and 365 nm, respectively). Using an optimized continuous-flow reactor, a throughput of 0.43 g/h was obtained for trans-n-isohumulone.https://www.mdpi.com/1420-3049/30/5/1002humuloneisohumulonephotochemistryflow chemistrygreen chemistryphotoisomerization
spellingShingle Bruce C. Hamper
Bradley Gallow
Gregory Giovine
Trevor Smith
Continuous-Flow Photochemical Isomerization of Humulones to Isohumulones
Molecules
humulone
isohumulone
photochemistry
flow chemistry
green chemistry
photoisomerization
title Continuous-Flow Photochemical Isomerization of Humulones to Isohumulones
title_full Continuous-Flow Photochemical Isomerization of Humulones to Isohumulones
title_fullStr Continuous-Flow Photochemical Isomerization of Humulones to Isohumulones
title_full_unstemmed Continuous-Flow Photochemical Isomerization of Humulones to Isohumulones
title_short Continuous-Flow Photochemical Isomerization of Humulones to Isohumulones
title_sort continuous flow photochemical isomerization of humulones to isohumulones
topic humulone
isohumulone
photochemistry
flow chemistry
green chemistry
photoisomerization
url https://www.mdpi.com/1420-3049/30/5/1002
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AT bradleygallow continuousflowphotochemicalisomerizationofhumulonestoisohumulones
AT gregorygiovine continuousflowphotochemicalisomerizationofhumulonestoisohumulones
AT trevorsmith continuousflowphotochemicalisomerizationofhumulonestoisohumulones