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Analogues of poison ivy urushiol. Synthesis and biological activity of disubstituted n-alkylbenzenes.

The total synthesis of different isomers and analogues of poison ivy urushiol is described. These include the positional isomers 1-5 and the nitrogen-containing analogues 6 and 8 and their mesylamino derivatives 7 and 9. 3,4-Dimethoxybenzaldehyde, m-dimethoxybenzene, resorcinol, and p-dimethoxybenzene were used as starting materials for compounds 1, 2, 3, and 4, respectively. Compound 5 is prepared by catalytic hydrogenation of bilobol isolated from Ginkgo biloba. Compounds 6 and 7 were prepared from anacardic acid as the starting material while compounds 8 and 9 were prepared from phenol as the starting material. Compounds 1-9 were tested for their ability to cross-react with poison ivy urushiol in sensitized guinea pigs. Compounds 6 and 8 were reactive at the 10-microgram dose level when applied topically, while compound 1 was a skin irritant at that dose. On the other hand, compounds 2-5, 7, and 9 showed no cross-reactivity up to the 30-micrograms dose level. Structural requirements for cross allergenicity are discussed.

Animals↗

Drugs derived from cannabinoids. 3. Sulfur analogs, thiopyranobenzopyrans and thienobenzopyrans.

Sulfur analogs of cannabinoids corresponding to DMHP (1) were prepared utilizing the Pechmann condensation between the appropriate keto ester and (5-(1,2-dimethylheptyl)resorcinol, followed by Grignard reaction. Compounds of various structural types (2-6), which had different ring size and position of the sulfur atom substituted in the alicyclic ring, were found to be active CNS agents in pharmacological tests in mice, rats, and dogs. They showed profiles qualitatively similar to those of the nitrogen and carbocyclic analogs. Basic esters of the most interesting parent phenols 2 and 4 were also prepared and tested.

Aggression↗

Drugs derived from cannabinoids. 6. Synthesis of cyclic analogues of dimethylheptylpyran.

Two cyclic analogues 8 and 9 of dimethylheptylpyran (DMHP, 1) were synthesized by the Pechmann condensation of the resorcinol 4 with ethyl 4-methyl-2-cyclohexanone-1-carboxylate followed by Grignard addition with MeMgI. In selected pharmacological tests both analogues 8 and 9 were considered inactive compared to DMHP as CNS and cardiovascular agents.

Animals↗

Oscillations in some linear free energy relationships derived from partition coefficients of phenols between octanol and water.

In the partition of some resorcinol alkyl ethers between water and 1-octanol, the values of delta Gtrs do not increase in a regular way. Odd and even chain alkyl compounds show different, regular increases in delta Gtrs for addition of each methylene group. The unrecognized occurrence of this phenomenon in earlier data is pointed out, and its possible significance in medicinal chemistry is discussed.

1-Octanol↗

Catechol derivatives of 6-aminobenzocycloheptene: assessment of dopaminergic effects.

The title compounds were prepared as congeners of the dopaminergically potent 2-amino-5,6-dihydroxytetralin series ("A-5,6-DTN"). None of the variously nitrogen-substituted benzocycloheptenes demonstrated any dopamine-like effects in a variety of assays. The primary amine had alpha 1-adrenoceptor stimulant effects. This lack of dopaminergic effect parallels the inactivity found in 6-aminobenzocycloheptenes bearing no oxygen substitutents, those bearing a single phenolic group, and those bearing a resorcinol 1,3-diphenolic substitution pattern.

Animals↗

Unsaturated side chain beta-11-hydroxyhexahydrocannabinol analogs.

The cannabinoid side chain is a key pharmacophore in the interaction of cannabinoids with their receptors (CB1 and CB2). To study the stereochemical requirements of the side chain, we synthesized a series of cannabinoids in which rotation around the C1'-C2' bond is blocked. The key steps in the synthesis were the cuprate addition of a substituted resorcinol to (+)-apoverbenone, the TMSOTf-mediated formation of the dihydropyran ring, and the stereospecific introduction of the beta-11-hydroxymethyl group. All the analogs tested showed nanomolar affinity for the receptors, the cis-hept-1-ene side chain having the highest affinity for CB1 (Ki = 0.89 nM) and showing the widest separation between CB1 and CB2 affinities. The parent n-heptyl-beta-11-hydroxyhexahydrocannabinol was the least potent binding to CB1 (Ki = 8.9 nM) and had the lowest selectivity between CB1 and CB2.

Animals↗

Structure--activity relationships of lysophosphatidic acid: conformationally restricted backbone mimetics.

Lysophosphatidic acid (LPA) has associated with it an intriguing cell biology that is thought to be mediated through its interaction with G-protein coupled receptor(s). In an effort to extend the structure-activity relationships of LPA, we have produced a series of LPA analogues in which the glycerol core in LPA was replaced with conformationally restricted aryl substructures. The aryl substructures encompassed aminophenol, resorcinol, dihydroxy benzophenone, and tocopherol systems. The benzophenone moiety was investigated both as a conformationally restricting substructure for LPA and as a possible photoreactive alkylating agent for the LPA receptor(s). All LPA analogues were evaluated for their potency and efficacy in mobilizing calcium ions from internal stores in MDA MB-231 cells. Ten of the 14 analogues exhibited activity in this assay at doses up to 5 microM; none of the compounds exhibited nonreceptor-mediated lytic activity at this maximal concentration. The receptor response showed surprising tolerance for manipulation in the backbone region of LPA, although none of the compounds were equipotent to LPA. This tolerance for a variety of structures has given us new leads into the realization of novel agonists and antagonists of the LPA receptor(s).

Calcium↗

Potent cyano and carboxamido side-chain analogues of 1', 1'-dimethyl-delta8-tetrahydrocannabinol.

The synthesis and pharmacological profile of several cyano (1a-e) and carboxamido (2a-h) side-chain-substituted analogues of 1', 1'-dimethyl-Delta8-THC are described. Commercially available cyano compound 3 was transformed to the resorcinol 6 in a three-step sequence. Condensation of 6 with p-menth-2-ene-1,8-diol formed the THC 7a which, with sodium cyanide/DMSO, gave 1b. Protection of the phenol in 7a as the MOM derivative provided the common intermediate 8 for the synthesis of 1a,c,e. Compound 1d was also synthesized from 7a via the aldehyde 9a. Base hydrolysis of 1b gave the acid 10 which, via its acid chloride and subsequent treatment with the appropriate amine, formed the target compounds 2a-h. The pharmacological profile indicated that the cyano analogues 1a-e had very high CB1 binding affinity (0.36-13 nM) and high in vivo potency as agonists. Two analogues (1a,b) had extremely high potency in the mouse tetrad tests. The dimethylcarboxamido analogue 2a showed a similar profile to 1a,b. The high potency was also retained in analogue 2c. In contrast the sulfonamide analogue 2d was unique as it had greater affinity than Delta9-THC, yet it was practically devoid of agonist effects. This study suggests that the incorporation of a cyano or an amide substituent in the side chain of Delta8-THC-DMH can enhance potency and can also lead to compounds with a unique profile which have high binding affinity and are practically devoid of agonist effects.

Animals↗

Modeling of the inhibition of retroviral integrases by styrylquinoline derivatives.

Styrylquinoline derivatives, known to be potent inhibitors of HIV-1 integrase, have been experimentally tested for their inhibitory effect on the disintegration reaction catalyzed by catalytic cores of HIV-1 and Rous sarcoma virus (RSV) integrases. A modified docking protocol, consisting of coupling a grid search method with full energy minimization, has been specially designed to study the interaction between the inhibitors and the integrases. The inhibitors consist of two moieties that have hydroxyl and/or carboxyl substituents: the first moiety is either benzene, phenol, catechol, resorcinol, or salicycilic acid; the hydroxyl substituents on the second (quinoline) moiety may be in the keto or in the enol forms. Several tautomeric forms of the drugs have been docked to the crystallographic structure of the RSV catalytic core. The computed binding energy of the keto forms correlates best with the measured inhibitory effect. The docking procedure shows that the inhibitors bind closely to the crystallographic catalytic Mg(2+) dication. Additional quantum chemistry computations show that there is no direct correlation between the binding energy of the drugs with the Mg(2+) dication and their in vitro inhibitory effect. The designed method is a leading way for identification of potent integrase inhibitors using in silico experiments.

Algorithms↗

Synthesis, aggregation, and binding behavior of synthetic amphiphilic receptors.

Amphiphilic bowl-shaped receptor molecules have been synthesized starting from diphenylglycoluril. Upon dispersion in water, these molecules self-assemble to form vesicles that bind neutral guests and alkali metal ions. In the case of bis(alkylester)-modified receptor compound 4, electron microscopy reveals that an increase in the size of the alkali metal ion (from Na(+) or K(+) to Rb(+) and to Cs(+)) leads to a change in the shape of the aggregates, viz. from vesicles to tubules. Monolayer experiments suggest that this behavior is due to a change in the conformation of this amphiphilic receptor. In water, molecules of 4 have an elongated conformation that changes to a sandwich-like one upon binding of alkali metal ions. Binding studies with vesicles from the bis-ammonium receptors 6 and 9 and the guest 4-(4-nitrophenylazo)resorcinol (Magneson) reveal that below the critical aggregation concentration (CAC) of the amphiphile 1:1 host-guest complexes are formed with high host-guest association constants. Above the CAC, a host-guest ratio of 2:1 was observed that indicates that only the cavities on the outside of the vesicle can be occupied. In the case of the naphthalene walled compound 8 changes in the vesicle structure are induced by the organic guest Magneson.

Chloroform↗

Synthesis of 2,3-dihydro-3-hydroxy-2-hydroxylalkylbenzofurans from epoxy aldehydes. One-step syntheses of brosimacutin G, vaginidiol, vaginol, smyrindiol, xanthoarnol, and Avicenol A. Biomimetic syntheses of angelicin and psoralen.

We have developed two practical one-step syntheses of 2,3-dihydro-3-hydroxy-2-hydroxyalkylbenzofurans from readily available optically pure alpha,beta-epoxy aldehydes. Electron-deficient resorcinols react with epoxy aldehydes using either Cs2CO3 in DMF or KOH/CaCl2 in MeOH to give adducts 13, 16, 18, 20, 21, and brosimacutin G (6t). Grignard reagents prepared by low-temperature halogen-metal exchange of acetoxy iodocoumarins 35d and 40 and acetoxy bromonaphthalene 41 add to epoxy aldehyde (S)-26 to complete the first syntheses of vaginidiol (7c), vaginol (7t), smyrindiol (8c), xanthoarnol (8t), and avicenol A (9t). Acid-catalyzed fragmentation of vaginidiol or vaginol provides angelicin, while that of smyrindiol or xanthoarnol affords psoralen. In both cases, the trans isomers fragment only twice as fast as the cis isomers, possibly through the intermediacy of a common benzylic cation. This may have implications for the biosynthesis of angelicin and psoralen.

Aldehydes↗

New insights into the geometry of resorc[4]arenes: solvent-mediated supramolecular conformational and chiroptical control.

The conformations of inherently chiral resorc[4]arenes were studied by circular dichroism (CD) spectroscopy. Whereas in aprotic solvents the crown conformation (C4) is preferred, protic solvents favor the boat conformation (C2). As a result of electronic coupling of the lowest L(b) state of the resorcinol unit in the resorc[4]arene, the CD spectra show a strong dependence on the conformation of the macrocycle. For the first time the solvent dependence of the CD spectra was qualitatively analyzed and simulated by using theoretical methods. We have thus demonstrated not only that the conformation of the calixarene is dramatically manipulated by the solvent but also that the joint use of chiroptical measurements and theoretical calculations is a powerful and versatile tool for elucidating structural variations in supramolecular chemistry.

Journal Article↗

Benzylic manganese halides, sulfonates, and phosphates: preparation, coupling reactions, and applications in organic synthesis

The use of highly active manganese, prepared by the Rieke method, for the direct preparation of benzylic manganese reagents was investigated. The oxidative addition of the highly active manganese (Mn) to benzylic halides was easily completed under mild conditions. More importantly, benzylic manganese sulfonates and phosphates were prepared by direct oxidative addition of Mn to the carbon-oxygen bonds of benzylic sulfonates and phosphates. The resulting benzylic manganese reagents were found to undergo cross-coupling reactions with a variety of electrophiles. The majority of these reactions were carried out in the absence of any transition metal catalyst under mild conditions. This approach also provided a facile synthetic route to the preparation of resorcinolic lipids.

Journal Article↗

Product screening of fast reactions in IR-laser-heated liquid water filaments in a vacuum by mass spectrometry.

In the present article a novel approach for rapid product screening of fast reactions in IR-laser-heated liquid microbeams in a vacuum is highlighted. From absorbed energies, a shock wave analysis, high-speed laser stroboscopy, and thermodynamic data of high-temperature water the enthalpy, temperature, density, pressure, and the reaction time window for the hot water filament could be characterized. The experimental conditions (30 kbar, 1750 K, density approximately 1 g/cm3) present during the lifetime of the filament (20-30 ns) were extreme and provided a unique environment for high-temperature water chemistry. For the probe of the reaction products liquid beam desorption mass spectrometry was employed. A decisive feature of the technique is that ionic species, as well as neutral products and intermediates may be detected (neutrals as protonated aggregates) via time-of-flight mass spectrometry without any additional ionization laser. After the explosive disintegration of the superheated beam, high-temperature water reactions are efficiently quenched via expansion and evaporative cooling. For first exploratory experiments for chemistry in ultrahigh-temperature, -pressure and -density water, we have chosen resorcinol as a benchmark system, simple enough and well studied in high-temperature water environments much below 1000 K. Contrary to oxidation reactions usually present under less extreme and dense supercritical conditions, we have observed hydration and little H-atom abstraction during the narrow time window of the experiment. Small amounts of radicals but no ionic intermediates other than simple proton adducts were detected. The experimental findings are discussed in terms of the energetic and dense environment and the small time window for reaction, and they provide firm evidence for additional thermal reaction channels in extreme molecular environments.

Chemistry↗

Surface area and microporosity of carbon aerogels from gas adsorption and small- and wide-angle X-ray scattering measurements.

A carbon aerogel was obtained by carbonization of an organic aerogel prepared by sol-gel polymerization of resorcinol and formaldehyde in water. The carbon aerogel was then CO(2) activated at 800 degrees C to increase its surface area and widen its microporosity. Evolution of these parameters was followed by gas adsorption and small- and wide-angle X-ray scattering (SAXS and WAXS, respectively) with contrast variation by using dry and wet (immersion in benzene and m-xylene) samples. For the original carbon aerogel, the surface area, S(SAXS), obtained by SAXS, is larger than that obtained by gas adsorption (S(ads)). The values become nearly the same as the degree of activation of the carbon aerogel increases. This feature is due to the widening of the narrow microporosity in the carbon aerogel as the degree of activation is increased. In addition, WAXS results show that the short-range spatial correlations into the assemblies of hydrocarbon molecules confined inside the micropores are different from those existing in the liquid phase.

Journal Article↗

Low-birefringent, chiral banana phase below calamitic nematic and/or smectic C phases in oxadiazole derivatives.

Bent-shaped molecules based on the oxadiazole central core with various side wings and terminal chain groups have been synthesized, and their liquid-crystalline behavior was investigated by optical microscopic, X-ray, and electrooptic measurements. These molecules exhibit liquid-crystal polymorphism including both the calamitic and banana phases. Such a characteristic polymorphism is attributable to the larger bend angle of the oxadiazole core compared to that of the resorcinol core used in conventional banana molecules. Only one type of banana phase, designated as the Bx phase, is formed. It appears upon cooling from the nematic and smectic liquid crystals and exhibits chiral domains with a very weak birefringence (apparently optically isotropic). By applying an electric field, the Bx phase is altered to a high-birefringence B2 phase with a homochiral SmC(A)P(A) structure that exhibits an antiferroelectric response. From detailed analyses of the optical texture and X-ray patterns through the transformation from well-oriented calamitic phases, the Bx phase was found to exhibit a helical structure, which arises as a frustration from the ground-state B2 phase in such a manner that the blocks of B2 layers are twisted with respect to each other in a direction parallel to the layer plane similarly to the twisted grain boundary (TGB) phase.

Journal Article↗

Changing surface hydro- and oleophobicity with resorcinarene multilayers-a simple water/oil proofing process.

Resorcinarenes (resorcinol-aldehyde tetramers) of appropriate structures have been shown to change the hydro- and oleophilicities of a variety of surfaces. The phenomenon results from attachment of the rim of the bowl-like molecules to hydrophilic surfaces. Hydrophobic (alkyl) and oleophobic (perfluoro alkyl) "legs" attached to the bowls then determine the immediate surface property. Amounts required to modify surfaces are only between 2 and 10 mg m(-2) treated, and there is evidence of multilayer formation. Penetration of surfaces by a variety of liquids has been studied and cannot easily be understood as a function of density, viscosity, or surface tension.

Absorption↗

In2O3 hollow microspheres: synthesis from designed In(OH)3 precursors and applications in gas sensors and photocatalysis.

In this work, well-shaped In(OH)3 hollow microspheres have been successfully prepared via a novel surfactant-free vesicle-template-interface route in the "formamide-resorcinol-water" system, in which spontaneous vesicles were formed under hydrothermal conditions and NH3 from the hydrolysis of formamide acted as the OH- provider. Morphological and structural characterizations indicate that the shells of as-prepared In(OH)3 hollow microspheres were constructed by numerous nanocubes about 80 nm in size. As desired, In2O3 hollow microspheres were obtained from annealing the designed In(OH)3 precursors, and the as-obtained In2O3 hollow microspheres performed well as a gas-sensing material in response to both ethanol and formaldehyde gases and as a photocatalyst for photocatalytic degradation of rhodamine B. The facile preparation method and the improved properties derived from special microstructures are significant in the synthesis and future applications of functional nanomaterials.

Journal Article↗