13673-95-5Relevant articles and documents
Phenylalanyl-tRNA synthetase of Escherichia coli K 10. Multiple enzyme-aminoacyl-tRNA complexes as a consequence of substrate specificity.
Guentner,Holler
, p. 2028 - 2038 (1979)
The interaction between Phe-tRNA(Phe) or other acyl-tRNA derivatives thereof and phenylalanyl-tRNA synthetase of Escherichia coli K 10 has been investigated by nonequilibrium dialysis, by fluorescence titration in the presence of 2-p-toluidinylnaphthalene-6-sulfonate, by the kinetics of the aminoacylation of tRNA(Phe), and by the kinetics of the catalytic hydrolysis of Phe-tRNA(Phe). Phe-tRNA(Phe), or derivatives thereof, forms two types of complexes with the synthetase. One type involves the attachment of the phenylalanyl moiety to the phenylalanine-specific site of the enzyme, and the other type, to the tRNA(Phe)-specific binding site. They resemble alternative modes of a destabilized enzyme-product complex and are predicted on the basis of thermodynamic considerations. The two modes of binding of acyl-tRNA compete with each other. The attachment of Phe-tRNA(Phe) to the phenylalanine-specific site dominates. At equilibrium, this complex is present at a fourfold higher concentration than the other type of complex. The HNO2 deaminated Phe-tRNA(Phe) binds exclusively to the site specific for L-phenylalanine. On the contrary, Ile-tRNA(Phe) adds at 94.1% to the tRNA(Phe)-specific site. The association of Phe-tRNA(Phe) with this site leads to enzymatic hydrolysis into L-phenylalanine and tRNA(Phe). The complex involving the phenylalanine-specific site is hydrolytically unproductive. L-Phenylalanine acts as an activator of the hydrolysis by occupying the amino acid specific site and by shifting the equilibrium between the complexes toward the binding ot Phe-tRNA(Phe) at the tRNA(Phe)-specific site. The association of Phe-tRNA(Phe) at the phenylalanine-specific site does not interfere sterically with the binding of free tRNA(Phe). The sequential addition of free and aminoacylated tRNA(Phe) exhibits negative cooperativity. Such a mechanism could help to expel the product from the enzyme.
Trifluoromethanesulonic acid catalyzed alkylation of arenes with methyl (2R)-glycidate
Linares-Palomino, Pablo J.,Prakash, G. K. Surya,Olah, George A.
, p. 1221 - 1225 (2005)
Methyl (R)-glycidate (= methyl (R)-oxiranecarboxylate; 2) in superacidic trifluoromethanesulfonic acid medium reacts with electron-rich arenes to give α-hydroxy-β-arylpropanoate derivatives 3a-3f with high stereospecificity. At the same time, the observed
Stereoselective Oxidation of Titanium(IV) Enolates with Oxygen
Gómez-Palomino, Alejandro,Romea, Pedro,Urpí, Fèlix
, p. 2721 - 2726 (2018/06/08)
A novel approach to synthesize enantiomerically pure α-hydroxy carboxylic derivatives is reported. A highly stereoselective oxidation of titanium(IV) enolates from chiral N -acyloxazolidinones is performed with oxygen under simple experimental conditions
Enantioselective, Catalytic Vicinal Difluorination of Alkenes
Scheidt, Felix,Sch?fer, Michael,Sarie, Jér?me C.,Daniliuc, Constantin G.,Molloy, John J.,Gilmour, Ryan
supporting information, p. 16431 - 16435 (2018/11/23)
The enantioselective, catalytic vicinal difluorination of alkenes is reported by II/IIII catalysis using a novel, C2-symmetric resorcinol derivative. Catalyst turnover via in situ generation of an ArIIIIF2 species is enabled by Selectfluor oxidation and addition of an inexpensive HF–amine complex. The HF:amine ratio employed in this process provides a handle for regioselective orthogonality as a function of Br?nsted acidity. Selectivity reversal from the 1,1-difluorination pathway (geminal) to the desired 1,2-difluorination (vicinal) is disclosed (>20:1 in both directions). Validation with electron deficient styrenes facilitates generation of chiral bioisosteres of the venerable CF3 unit that is pervasive in drug discovery (20 examples, up to 94:06 e.r.). An achiral variant of the reaction is also presented using p-TolI (up to >95 % yield).
