The isomerization products of humulone

Alderweireldt, F. C.; Verzele, M.; Anteunis, M.; Dierckens, J.

doi:10.1002/bscb.19650740107

Cited by 60 publications

(10 citation statements)

References 9 publications

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“…In the chromatography, humulinones (cohumulinone (5a), n-humulinone (5b), and adhumulinone (5c)) were eluted earlier than iso-α-acids (Figure 2C). In detail, 5a and 5b, which existed as racemic mixtures (4S5R and 4R5S, Figure 3), 15,32,33 were detected as single peaks, and 5c, which existed as two diastereomers due to the additional fixed chiral carbon (2‴S) in the acyl side chain (5c, 5c′, Figure 3), 25,33 was detected as two equal intensity peaks (5c, 5c′) (Figure 2C). Thus, it was confirmed that this analytical method could separate all of the congeners belonging to humulinones, including the diastereomers of adhumulinone.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Identification and Quantification of the Oxidation Products Derived from α-Acids and β-Acids During Storage of Hops (Humulus lupulus L.)

Taniguchi

Matsukura

Ozaki

et al. 2013

J. Agric. Food Chem.

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α-Acids and β-acids, two main components of hop resin, are known to be susceptible to oxygen and degraded during hop storage, although the oxidation products in stored hops have not been fully identified. In this study, we developed a high-performance liquid chromatography (HPLC) analysis method suitable for separation and quantification of the oxidation products. This HPLC analysis clearly proved, for the first time, that humulinones and hulupones are major products in oxidized hops. We are also the first to identify novel 4'-hydroxy-allohumulinones, suggested to be oxidative products of humulinones, by means of NMR spectroscopy and high-resolution mass spectrometry. Using the developed analytical method, changes in α- and β-acids and their oxidation products during hop storage were clearly revealed for the first time.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Identification and Quantification of the Oxidation Products Derived from α-Acids and β-Acids During Storage of Hops (Humulus lupulus L.)

Taniguchi

Matsukura

Ozaki

et al. 2013

J. Agric. Food Chem.

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“…The alternative (1,2) shift would lead to a y-pyrone structure 14, which has no chance to be decarbonylated.…”

Section: Second O X I D a T I O N S T E P B E F O R E R I N G C L O Smentioning

confidence: 98%

New Members of the hop anti iso‐α‐Acids Series

Taeye

Keukeleire

Verzele

1979

Bulletin des Soc Chimique

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Two new compounds, 4-hydroxy-5-~3-methyIbutanoyl)-2-~3-methyl-2-butenyl~fu-ran (2H) -3-one (5) and 2-(3-methyl-2-butenyl) -4-ethanoyl-3,4-dihydroxy-5-(2-methylpropylidene)-2-cyclopentenel-one (12) have been isolated from isomerisation reaction mixtures of humulone (L). A s both formation mechanisms show, the compounds are rearranged derivatives of the hop anti rso-a-acids.Humulone (1, scheme l), the main hop a-acid, can easily be isomerised to the 1 epimeric isohumulones (2, scheme 1) in different circumstances . Recently, it was shown that the ring contraction, via acyloin rearrangement, occurs partially in an alternative way, yielding the anti isohumulones (?, scheme 1) and derivatives . The specific features, which push the rearrangement in one or the other direction, were also discussed3.lone (4, scheme 1) and derivatives have been isolated and characterised . The total yield of the hop anti iso-a-acids and derivatives amounts to 10 %, which is quite important in view of their extremely strong bittering power .TWO new members are now added to the hop anti iso-a-acids family. 2In addition, deacylated anti isohumu- The band with distribution coefficient 0.3 contains 5, which has, according to mass spectral data, an elerent;ll fonnula of C14~2000?. The UV-characteristics exclude the presence of the commonly encountered 6-tricarbonyl or 8-dicarbonyl systems in hopThe structure is revealed by 300 MHz 'H-NMR. Only one 3-methyl-2-butenyl side chain of 1 remains, while analysis unravels two spin systems, ABXY and ABX respectively. Due to broadening of the X-part at 6 5.04 by long range couplings, no values of coupling constants can be extracted. Measurements at Bevoegdverklaard Navorser of the Belgian "Nationaal Fonds voor Wetenschappelijk Onderzoek" .-a 7 -

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“…Glycols were reacted with acetone or the dimethyl acetal, according to procedures already described [16,17], or via the glycol sulfite and acetone as reported for aldehydes [17]. Some other dioxanes and dioxolanes were synthesized for comparative purposes (f.i.…”

Section: -Methyl-i 2-propanediolmentioning

confidence: 99%

NMR Experiments on Acetals: XXIX. The Ease of Acetonide Formation of Some Glycols

Anteunis

Rommelaere

1970

Bulletin des Soc Chimique

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The ease of acetonide formation for some 1,2-and 1,3-glycols is mzasured and in the discussion of the equilibrium data (tables I and 11). obtained by quantitative evaluation as a function of temperature, emphasis is placed upon the pronounced entropy decrease, and its consequence in the interpretation. All cyclizations are found to be favoured by enthalpy decreases but are governed by entropy changes.The studies on the conductivity of boric acid in the presence of glycols, and the studies on chemical equilibration of these glycols with acetone by Boeseken [l] may be considered as the start of conformational information on heterocyclic compounds. Since then, these and other results, have been used to correlate constitution and conformation with reactivity, and such aspects were of a fundamental nature for the study of natural polyhydroxylic compounds. It is therefore surprising to find rather scarce information with respect to detailed thermodynamic parameters which govern the acetalization. It is obvious, that in order to obtain substantial information, it does not suffice to rely upon observed equilibrium states obtained at one temperature only.We began the study of acetal cyclization by a reinvestigation of the acetonide formation of several glycols and the determination of the equilibrium states as a function of temperature by quantitative nmr spectroscopy. The data obtained for mixtures of acetone and glycols are gathered in tables I and 11. DISCUSSION OF THE TABLES General Aspects1. Although all the reactions are favoured by a decrease of enthalpy, they all are characterized by unfavorable entropy changes. This is not unexpected because during cyclization a diol molecule is replaced by a more associated water molecule.Therefore the gross portion of the observed entropy decrease must be attributed to the concurrent decrease in translational freedom. Those rare reactions which occur almost isoentropically are probably characterised by an increase of rotational and/or vibrational freedom. All discussions on entropy changes in this paper are of comparative nature, and cannot be done on an absolute basis. One of the most striking features, especially when one limits the discussion to a homologous series, is the nearly constant ratio of AH" versus ASo (tableII, nosl,

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The isomerization products of humulone

Cited by 60 publications

References 9 publications

Identification and Quantification of the Oxidation Products Derived from α-Acids and β-Acids During Storage of Hops (Humulus lupulus L.)

Identification and Quantification of the Oxidation Products Derived from α-Acids and β-Acids During Storage of Hops (Humulus lupulus L.)

New Members of the hop anti iso‐α‐Acids Series

NMR Experiments on Acetals: XXIX. The Ease of Acetonide Formation of Some Glycols

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