- 2-Diazo-1-(4-hydroxyphenyl)ethanone: A versatile photochemical and synthetic reagent
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α-Diazo arylketones are well-known substrates for Wolff rearrangement to phenylacetic acids through a ketene intermediate by either thermal or photochemical activation. Likewise, α-substituted p-hydroxyphenacyl (pHP) esters are substrates for photo-Favorskii rearrangements to phenylacetic acids by a different pathway that purportedly involves a cyclopropanone intermediate. In this paper, we show that the photolysis of a series of α-diazo-p- hydroxyacetophenones and p-hydroxyphenacyl (pHP) α-esters both generate the identical rearranged phenylacetates as major products. Since α-diazo-p-hydroxyacetophenone (1a, pHP N2) contains all the necessary functionalities for either Wolff or Favorskii rearrangement, we were prompted to probe this intriguing mechanistic dichotomy under conditions favorable to the photo-Favorskii rearrangement, i.e., photolysis in hydroxylic media. An investigation of the mechanism for conversion of 1a to p-hydroxyphenyl acetic acid (4a) using time-resolved infrared (TRIR) spectroscopy clearly demonstrates the formation of a ketene intermediate that is subsequently trapped by solvent or nucleophiles. The photoreaction of 1a is quenched by oxygen and sensitized by triplet sensitizers and the quantum yields for 1a-c range from 0.19 to a robust 0.25. The lifetime of the triplet, determined by Stern-Volmer quenching, is 31 ns with a rate for appearance of 4a of k = 7.1 × 10 6 s-1 in aq. acetonitrile (1:1 v:v). These studies establish that the primary rearrangement pathway for 1a involves ketene formation in accordance with the photo-Wolff rearrangement. Furthermore we have also demonstrated the synthetic utility of 1a as an esterification and etherification reagent with a variety of substituted α-diazo-p- hydroxyacetophenones, using them as synthons for efficiently coupling it to acids and phenols to produce pHP protect substrates. The Royal Society of Chemistry and Owner Societies.
- Senadheera, Sanjeewa N.,Evans, Anthony S.,Toscano, John P.,Givens, Richard S.
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p. 324 - 341
(2014/02/14)
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- Halogenation of 4-hydroxy/amino-3-methoxyphenyl acetamide TRPV1 agonists showed enhanced antagonism to capsaicin
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As an extension of our analysis of the effect of halogenation on thiourea TRPV1 agonists, we have now modified selected 4-hydroxy(or 4-amino)-3- methoxyphenyl acetamide TRPV1 agonists by 5- or 6-halogenation on the aromatic A-region and evaluated them for potency for TRPV1 binding and regulation and for their pattern of agonism/antagonism (efficacy). Halogenation shifted the functional activity at TRPV1 toward antagonism with a greater extent of antagonism as the size of the halogen increased (I > Br > Cl), as previously observed for the thiourea series. The extent of antagonism was greater for halogenation at the 5-position than at the 6-position, in contrast to SAR for the thiourea series. In this series, compounds 55 and 75 showed the most potent antagonism, with Ki (ant) = 2.77 and 2.19 nM, respectively, on rTRPV1 expressed in Chinese hamster ovary cells. The compounds were thus ca. 40-60-fold more potent than 6′-iodononivamide.
- Kang, Dong Wook,Kim, Yong Soo,Lim, Kwang Su,Kim, Myeong Seop,Pearce, Larry V.,Pavlyukovets, Vladimir A.,Tao, Andy K.,Lang-Kuhs, Krystle A.,Blumberg, Peter M.,Lee, Jeewoo
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experimental part
p. 8092 - 8105
(2011/01/13)
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- Synthesis and in vitro evaluation of a novel iodinated resiniferatoxin derivative that is an agonist at the human vanilloid VR1 receptor
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Using a 'directed' iodination procedure, novel iodo-resiniferatoxin congeners were synthesized from 4-acetoxy-3-methoxyphenylacetic acid and resiniferinol- 9,13,14-ortho-phenylacetate (ROPA). The 2-iodo-4-hydroxy-5-methoxyphenylacetic acid ester of resini
- McDonnell, Mark E.,Zhang, Sui-Po,Dubin, Adrienne E.,Dax, Scott L.
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p. 1189 - 1192
(2007/10/03)
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- Vanilloids. 1. Analogs of Capsaicin with Antinociceptive and Antiinflammatory Activity
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As part of a program to establish structure-activity relationships for vanilloids, analogs of the pungent principle capsaicin, the alkyl chain portion the parent structure (and related compounds derived from homovanillic acid) was varied.In antinociceptive and antiinflammatory assays (rat and mouse hot plate and croton oil-inflamed mouse ear), compounds with widely varying alkyl chain structures were active.Short-chain compounds were active by systemic administration in the assays mentioned above but they retained the high pungency and acute toxicity characteristic of capsaicin.In contrast, the long chain cis-unsaturates, NE-19550 (vanillyloleamide) and NE-28345 (oleylhomovanillamide), were orally active, less pungent, and less acutely toxic than capsaicin.The potential of these compounds as antiinflammatory/analgesic agents is discussed in light of recent data on the mechanism of action of vanilloids on sensory nerve fibers.
- Janusz, John M.,Buckwalter, Brian L.,Young, Patricia A.,LaHann, Thomas R.,Farmer, Ralph W.,et al.
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p. 2595 - 2604
(2007/10/02)
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- Compounds and compositions having anti-inflammatory and analgesic activity
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Substituted phenylacetic acid amide compounds, and pharmaceutically-acceptable salts thereof, of the formula: STR1 wherein X is O or S; R1 is H, OH or CH3 ; R2 is straight chain alkenyl, branched chain or cyclic hydrocarbo
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