6997-34-8

The effect of the solvent composition in the binary mixtures of water with dimethyl sulfoxide, acetonitrile and 1,4-dioxane on the positions of absorption bands in the UV spectra of five guaiacylic phenols, as well as of the corresponding phenolate anions

The vanillyl-alcohol oxidase (VAO) family is a rich source of biocatalysts for the oxidative bioconversion of phenolic compounds. Through genome mining and sequence comparisons, we found that several family members lack a generally conserved catalytic aspartate. This finding led us to study a VAO-homolog featuring a glutamate residue in place of the common aspartate. This 4-ethylphenol oxidase from Gulosibacter chungangensis (Gc4EO) shares 42 % sequence identity with VAO from Penicillium simplicissimum, contains the same 8α-N3-histidyl-bound FAD and uses oxygen as electron acceptor. However, Gc4EO features a distinct substrate scope and product specificity as it is primarily effective in the dehydrogenation of para-substituted phenols with little generation of hydroxylated products. The three-dimensional structure shows that the characteristic glutamate side chain creates a closely packed environment that may limit water accessibility and thereby protect from hydroxylation. With its high thermal stability, well defined structural properties and high expression yields, Gc4EO may become a catalyst of choice for the specific dehydrogenation of phenolic compounds bearing small substituents.

A novel method for the preparation of isoeugenol, [ring-(U)-14C] is presented. Phenols and phenyl esters substituted in the para position with 1-hydroxyethyl or 1-hydroxypropyl acetate esters when treated with 1,8-diazabicyclo[5.4.0]undec-7-ene in dimethylformamide (DMF) eliminate the alkyl carboxylate function to give the unsaturated compound. The reaction fails with unsubstituted or ether substituted phenyl 1-hydroxyacetate esters.

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.

The synthesis of 1,2-dihydronaphthalenes and spiro[4.5]decatrienones via reaction of an allenyl-silane and a benzylic cation is reported.

Apocynin (4-hydroxy-3-methoxyacetophenone) and a few of its side chain homologues have been synthesized by a simple two-step procedure.The key step in the synthesis involves Grignard reaction between vanillin acetate and different haloalkanes.The carbinols thus generated have been dehydrogenated to the desired compounds by stirring with DDQ in benzene.The synthesised compounds show consistent choleretic activity in experimental animals.