22805-42-1Relevant articles and documents
Stereochemically probing the photo-favorskii rearrangement: A mechanistic investigation
Givens, Richard S.,Rubina, Marina,Stensrud, Kenneth F.
, p. 1709 - 1717 (2013/03/28)
Using model (R)-2-acetyl-2-phenyl acetate esters of (S)- or (R)-α-substituted-p-hydroxybutyrophenones (S,R)-12a and (R,R)-12b, we have shown that a highly efficient photo-Favorskii rearrangement proceeds through a series of intermediates to form racemic rearrangement products. The stereogenic methine on the photoproduct, rac-2-(p-hydroxyphenyl)propanoic acid (rac-9), is formed by closure of a phenoxy-allyloxy intermediate 17 collapsing to a cyclopropanone, the Favorskii intermediate 18. These results quantify the intermediacy of a racemized triplet biradical 316 on the major rearrangement pathway elusively to the intermediate 18. Thus, intersystem crossing from the triplet biradical surface to the ground state generates a planar zwitterion prior to formation of a Favorskii cyclopropanone that retains no memory of its stereochemical origin. These results parallel the mechanism of Dewar and Bordwell for the ground state formation of cyclopropanone 3 that proceeds through an oxyallyl zwitterionic intermediate. The results are not consistent with the stereospecific SN2 ground state Favorskii mechanism observed by Stork, House, and Bernetti. Interconversion of the diastereomeric starting esters of (S,R)-12a and (R,R)-12b during photolysis did not occur, thus ruling out leaving group return prior to rearrangement.
NANOSTRUCTURED METALS
-
Page/Page column 13, (2012/06/16)
The invention relates to a nanoparticulate material comprising long ultrathin metal nanowires, and to processes for making it. The nanoparticulate material may be used as a catalyst and, in the presence of a chiral modifier, can catalyse enantioselective reactions.
Identification of dihydrogalangal acetate in galangal [Alpinia galangal (L.) Swartz] extracts
Yang, Xiaogen,Rohr, Martin,Jordan, Jason
experimental part, p. 3286 - 3290 (2010/06/14)
Dihydrogalangal acetate has been discovered for the first time in galangal roots [Alpinia galangal (L.) Swartz]. The compound has a taste sensation similar to galangal acetatesthe pungent principle of galangalsbut it is more stable in food and beverage applications. Therefore, dihydrogalangal acetate provides many advantages as a flavor ingredient for alcohol enhancement and taste modification. Dihydrogalangal acetate is present in approximately 0.0005% of fresh roots and in about 0.004% of dried roots. (S)-Dihydrogalangal acetate is found as the main optical isomer in galangal roots (98%), while its minor (R)-isomer is less abundant (2%). Enantiomers of galangal acetate and dihydrogalangal acetate were separated and evaluated by sensory analysis. (R)-Galangal acetate has a very faint woody and sweet aroma, and (R)-dihydrogalangal acetate is almost odorless, while (S)-galangal acetate has strong and (S)-dihydrogalangal acetate has weak pungent and woody notes. Although the aroma characters of these optical isomers are different, taste sensations were found to have no significant differences among galangal acetate, dihydrogalangal acetate, and their optical isomers.
Structure-activity relationships of 1′S-1′-acetoxychavicol acetate for inhibitory effect on NO production in lipopolysaccharide-activated mouse peritoneal macrophages
Matsuda, Hisashi,Ando, Shin,Morikawa, Toshio,Kataoka, Shinya,Yoshikawa, Masayuki
, p. 1949 - 1953 (2007/10/03)
1′S-1′-Acetoxychavicol acetate from the rhizomes of Alpinia galanga inhibited nitric oxide (NO) production in lipopolysaccharide-activated mouse peritoneal macrophages with an IC50 value of 2.3 μM. To clarify the structure-activity relationship of 1′S-1′- acetoxychavicol acetate, various natural and synthetic phenylpropanoids and synthetic phenylbutanoids were examined, and the following structural requirements were clarified. (1) The para or ortho substitution of the acetoxyl and 1-acetoxypropenyl groups at the benzene ring was essential. (2) The S configuration of the 1′-acetoxyl group was preferable. (3) The presence of the 3-methoxyl group and disappearance of the 2′-3′ double bond by hydrogenation reduced the activity. (4) The substitution of acetyl groups with propionyl or methyl groups reduced the activity. (5) Lengthening of the carbon chain between the 1′- and 2′-positions reduced the activity.
Synthesis and Antimicrobial Activity of Hydroxyalkyl- and Hydroxyacyl-phenols and Their Benzyl Ethers
Krauss, J.,Unterreitmeier, D.
, p. 94 - 98 (2007/10/03)
New phenolic compounds with hydrophilic side chains were prepared from 4-benzyloxybenzaldehyde and alkenyl magnesium bromides, followed by Sharpless dihydroxylation and hydrogenolytic removal of the benzyl group. The resulting compounds were tested in an agar diffusion assay against gram positive bacteria, gram negative bacteria, and against the fungi Candida glabrata and Aspergillus niger.
Formal Cycloaddition of Benzylic Cations with Alkenes
Angle, Steven R.,Arnaiz, Damian O.
, p. 5937 - 5947 (2007/10/02)
The reaction of benzylic cations with styrenes affords dihydro(1H)indenes in good yield via a formal atom cycloadditon.The cations were generated from quinone methides and benzylic alcohols. (E)-Styrenes participate in the reaction with remarkable stereoselectivity affording dihydro(1H)indenes with three stereogenic centers with >40:1 diastereoselectivity.A possible transition state for the reaction is discussed.Less activated alkenes such as dihydropyran and methylcyclohexane afforded cycloadducts in 66percent and 51percent yields, respectively.
Regio- and Chemo-selective Properties of Lipase from Candida cylindracea
Pedrocchi-Fantoni, Giuseppe,Servi, Stefano
, p. 1029 - 1034 (2007/10/02)
Lipase from Candida cylindracea allows discrimination between the two connectively non-equivalent hydroxy groups in primary diols or their esters via acylation-hydrolysis, with high regioselectivity.The same technique is used to distinguish between hydroxy groups of different nature in phenolic compounds.
Synthesis of 1,2-dihydronaphthalenes and spiro[4.5]-deca-3,6,9-trien-8-ones from benzylic alcohols
Angle,Arnaiz
, p. 2327 - 2330 (2007/10/02)
The synthesis of 1,2-dihydronaphthalenes and spiro[4.5]decatrienones via reaction of an allenyl-silane and a benzylic cation is reported.
