The enantiomeric composition of products obtained from isomerization of n-humulone 1a to trans- and cis-n-isohumulones 2a and 3a, respectively, was determined by chiral HPLC analysis of the isolated trans and cis isomers. Enantiomers of humulone 1 were readily resolved on a Whelk-O1 chiral stationary phase (CSP), whereas the isomeric isohumulones 2 and 3 were separated on a carbohydrate-based IC-3 CSP. Magnesium-catalyzed isomerization of n-humulone under basic conditions gave mixtures of trans- and cis-n-isohumulones exhibiting an increasing preference for the cis isomer at lower temperatures. At either 10 °C in CH2Cl2/H2O or reflux in methanol-water, the trans-(−) (4S,5S)-2a isomer was obtained in greater than 95% ee, while diastereomeric cis-3a exhibited 88% ee of the (+)-(4S,5R) enantiomer. Precision continuous flow photochemical isomerization using 395 nm LEDs provided trans-(−)-2a in greater than 95% ee in an isolated yield of 93%. However, photochemical isomerization with 365 nm LEDs gave a mixture of isomers consisting of 46% ee for the trans-(−)-2a and greater than 95% ee for the cis-(−)-(4R,5S)-3a enantiomer. The photochemically obtained (−)-3a isomer has the opposite absolute configuration compared to thermal isomerization. An oxadi-π-methane rearrangement is proposed to account for the formation of isohumulone isomers under photochemical conditions.

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.

Deuterated isohumulones can be prepared directly from humulones by an acyloin ring contraction under either magnesium-catalyzed basic conditions or by photochemical-induced reactions in deuterated solvents. Reactions of humulones with biphasic methylene chloride/aqueous NaOD and MgSO4 in D2O leads to stereoselective formation of cis-d (3)-isohumulones (cis/trans ratio of 82:18) as the magnesium salts in yields of 71-83%. Greater than 95% incorporation of three deuterons is observed at the C5 position of the pentenone ring and the methylene position of the C4 acyl group. Photochemical isomerization with a 400 nm blue LED source enables stereospecific formation of deuterated trans-isohumulones in 36-82% yield with greater than 95% incorporation of deuterium at the C5 ring position. Oxidation of humulones with cumene hydroperoxide in basic D2O gives isohumulinones with partial 55-73% incorporation of deuterium due to keto-enol isomerization of the methylene substituent of the C4 acyl group. The structural identities of the deuterated products are determined by a combination of negative-mode electrospray mass spectrometry (MS-ESI-) and 2D heteronuclear proton-carbon HMQC NMR analysis.

The contribution of hops to the bitter flavors in beer is complicated by a number of factors, including the relative concentrations of humulone homologs in hops, the extraction of bittering compounds from hops, and the conversion of humulones to isohumulones during the brewing process. In this study, we describe a rapid liquid chromatography-mass spectroscopy (LC-MS) method using electrospray ionization (ESI) coupled with selective ion monitoring mass spectroscopy (SIM-MS) for analysis of humulone and isohumulone content in beer. Individual beer samples are monitored directly following filtration and decarbonization. Using multiple injections in a single experimental run (MISER), data were collected in as little as 7 min per beer sample. Results were displayed as a single "misergram," which allowed for the convenient analysis of relative concentrations of humulones and isohumulones or hops utilization in sets of in-house brewed beers and commercial samples.

"Beer Brewing: Chemical and Biochemical Principles" is a 15 week laboratory and lecture course specifically designed for nonscience majors as an introduction to science literacy via structured laboratory experiments that encourage student engagement. It provides students with a foundation in chemical and biochemical principles using a comprehensive theme of brewing beer. The first part of the course introduces students to basic concepts of measurement, matter, atoms, molecules, and compounds. These ideas are related to the composition of beer and the four fundamental ingredients for preparation of beer: malted grain, water, hops, and yeast. Hands on laboratory exercises build on these concepts through the measurement of specific gravity, pH, specific ions, flavor components, and alcohol content of appropriate liquids. Organic and biochemical principles are investigated through the measurement of mashing kinetics, evaluation of changes in wort during the brewing process, and determination of beer bitterness by the measurement of hops derived compounds. Within specific guidelines, each student team prepares a recipe for a different style of beer. The culmination of the course is brewing of that beer and the analysis of the final product in terms of alcohol by volume, carbohydrate content, and bitterness. Collaboration and sensory evaluation are introduced through field trips to local breweries.

The chemical analysis of hop-derived humulone and isohumulone components in hops and beer was investigated using multiple injections in a single experimental run (MISER) extracted ion LC-MS. Comparative analysis of the humulone and lupulone contents of 12 hop varieties was accomplished in a 12 min run, an equivalent time of 1 min per hop sample. Rapid analysis of a group of 70 different beers in 74 min provided a comparative assessment of the amount of humulones (a-acids) and the isomerized isohumulones (iso-a-acids) present, also in an equivalent time of 1 min per sample. The relative humulone/isohumulone content was evaluated in a scatter plot, which allowed profiling of various craft and commercial beer styles. The MISER LC-MS approach allows for high-throughput analysis and a significant time savings. Together, these provide opportunities for increasing analysis sampling in production or a simple, rapid chemical analysis to accompany educational or classroom instruction.

Acrylohydroxamic acid, which is a useful monomer for the preparation of polymeric materials, has been prepared in a straightforward, two-step synthesis from readily available starting materials. The key steps are coupling of acrylic acid with O-tetrahydropyranylhydroxyl amine to provide protection of the hydroxylamine functionality, followed by acid cleavage of the protecting group.

Matrix metalloproteinase-13 (MMP-13) is a zinc-dependent protease responsible for the cleavage of type II collagen, the major structural protein of articular cartilage. Degradation of this cartilage matrix leads to the development of osteoarthritis. We previously have described highly potent and selective carboxylic acid containing MMP-13 inhibitors; however, nephrotoxicity in preclinical toxicology species precluded development. The accumulation of compound in the kidneys mediated by human organic anion transporter 3 (hOAT3) was hypothesized as a contributing factor for the finding. Herein we report our efforts to optimize the MMP-13 potency and pharmacokinetic properties of non-carboxylic acid leads resulting in the identification of compound 43a lacking the previously observed preclinical toxicology at comparable exposures.

Chromatographic separation of the enantiomers of parent compounds dimethyl α-hydroxyallyl phosphonate and 1-(dimethoxyphosphoryl) allyl methyl carbonate was demonstrated by high-performance liquid chromatography (HPLC) using Chiralpak AS-H and ad-H chiral stationary phases (CSP), respectively, using a combination of UV, polarimetric, and refractive index detectors. A comparison was made of the separation efficiency and elution order of enantiomeric α-hydroxyallyl phosphonates and their carbonate derivatives on commercially available polysaccharide AS, ad, OD, IC-3, and Whelk-O 1 CSPs. In general, the α-hydroxyallyl phosphonates were resolved on the AS-H CSP, whereas the carbonate derivatives and were preferentially resolved on the ad-H CSP. The impact of aryl substitution on the resolution of analytes and was evaluated. Thermodynamic parameters determined for enantioselective adsorption hydroxyphosphonates and on the AS-H CSP and carbonate on the ad-H CSP demonstrated enthalpic control for separation of the enantiomers. Chirality 28:656-662, 2016. © 2016 Wiley Periodicals, Inc.

The preparation of (S)- and (R)-1-(dimethoxyphosphoryl)allyl methyl carbonates is achieved on multigram scale from commercially available dimethyl phosphite and acrolein in three steps. The key steps involve an asymmetric Pudovik reaction and enzyme-catalyzed kinetic resolution.

The use of state-of-the-art separation tools from the pharmaceutical industry for addressing intractable separation problems from academic synthetic chemistry is evaluated, showing fast and useful results for the resolution of complex mixtures, separation of closely related components, visualization of difficult to detect compounds and purification of synthetic intermediates. Some recommendations for potential near term deployment of separation tools within academia and the evolution of next generation separation technologies are discussed.

Hematopoietic prostaglandin D synthase (HPGDS) is primarly expressed in mast cells, antigen-presenting cells, and Th-2 cells. HPGDS converts PGH(2) into PGD(2), a mediator thought to play a pivotal role in airway allergy and inflammatory processes. In this letter, we report the discovery of an orally potent and selective inhibitor of HPGDS that reduces the antigen-induced response in allergic sheep.

Combination of the structure-based design and solid-phase parallel synthesis provided an integrated approach to rapidly develop the structure-activity relationship of benzopyran COX-2 inhibitors. Binding free energies predicted by free energy perturbation theory yielded good agreement with experimental results. New potent and selective lead compounds with improved metabolic properties were identified.

Potent, highly selective and orally-bioavailable MMP-13 inhibitors have been identified based upon a (pyridin-4-yl)-2H-tetrazole scaffold. Co-crystal structure analysis revealed that the inhibitors bind at the S(1)(') active site pocket and are not ligands for the catalytic zinc atom. Compound 29b demonstrated reduction of cartilage degradation biomarker (TIINE) levels associated with cartilage protection in a preclinical rat osteoarthritis model.

A solid-phase organic synthesis method has been developed for the preparation of trisubstituted pyrimidin-6-one carboxylic acids 12, which allows elaboration to a 3-dimensional combinatorial library. Three substituents are introduced by initial Knoevenagel condensation of an aldehyde and malonate ester resin 7 to give resin bound 1. Cyclization of 1 with an N-substituted amidine 10, oxidation, and cleavage afforded pyrimidinone 12. The initial solid-phase reaction sequence was followed by gel-phase (19)FNMR and direct-cleavage (1)H NMR of intermediate resins to determine the optimal conditions. The scope of the method for library production was determined by investigation of a 3 x 4 pilot library of twelve compounds. Cyclocondensation of N-methylamidines and 7 followed by CAN oxidation gave mixtures of the resin bound pyrimidin-6-one 11 and the regioisomeric pyrimidin-4-one 15, which after cleavage from the resin afforded a nearly 1:1 mixture of pyrimidin-6-one and pyrimidin-4-one carboxylic acids 12 and 16, respectively. The regiochemical assignment was confirmed by ROESY1D and gHMBC NMR experiments. A library was prepared using 8 aldehydes, 3 nitriles, and 4 amines to give a full combinatorial set of 96 pyrimidinones 12. Confirmation of structural identity and purity was carried out by LCMS using coupled ELS detection and by high-throughput flow (1)H NMR.