14173-40-1Relevant articles and documents
Beam-induced dehalogenation in LSIMS: Effect of halogen type and matrix chemistry
Theberge,Bertrand
, p. 163 - 171 (1995)
The LSIMS beam-induced dehalogenation of several 4-halo-phenylalanine methyl esters (I, Br, Cl, F) was investigated and compared to that of atrazine using 12 different matrix compounds including diethyl phthalate for which the empirical electron affinity was known. The extent of dehalogenation, induced by a one-electron reduction process, is in agreement with the leaving group ability of the corresponding halogens (I > Br > Cl > F) and the dehalogenation inhibiting efficiency of the matrices. The latter is rationalized in terms of electron scavenging capacity and matrix structural features relating to that capacity. The extent of dehalogenation observed for 4-I-phenylalanine methyl ester is similar to that of atrazine, a chlorinated compound, which indicates that the halogen effect is not overwhelming in determining the extent of dehalogenation. The bracketing of matrix reduction potential was attempted based on the propensity of the matrices to induce M+. formation from analytes of known oxidation potentials. The ability of matrices to induce M+. formation parallels their dehalogenation and reduction inhibiting efficiencies. The last observation underlines the importance of matrix redox properties in effecting or inhibiting beam-induced processes, be they reductive or oxidative.
Pd-catalyzed dimethylation of tyrosine-derived picolinamide for synthesis of (S)-N-Boc-2,6-dimethyltyrosine and its analogues
Wang, Xuning,Niu, Songtao,Xu, Lanting,Zhang, Chao,Meng, Lingxing,Zhang, Xiaojing,Ma, Dawei
supporting information, p. 246 - 249 (2017/11/27)
A short and efficient synthesis of (S)-N-Boc-2,6-dimethyltyrosine utilizing palladium-catalyzed directed C-H functionalization is described. This represents the first general method for the ortho-dimethylation of tyrosine derivatives and offers a practical approach for preparing this synthetically important building block. Notably, throughout the reaction sequence no racemization occurs at the susceptible a-chiral centers.
Enzymatic synthesis of chiral phenylalanine derivatives by a dynamic kinetic resolution of corresponding amide and nitrile substrates with a multi-enzyme system
Yasukawa, Kazuyuki,Asano, Yasuhisa
supporting information, p. 3327 - 3332 (2013/01/15)
Mutant α-amino-ε-caprolactam (ACL) racemase (L19V/L78T) from Achromobacter obae with improved substrate specificity toward phenylalaninamide was obtained by directed evolution. The mutant ACL racemase and thermostable mutant D-amino acid amidase (DaaA) from Ochrobactrum anthropi SV3 co-expressed in Escherichia coli (pACLmut/pDBFB40) were utilized for synthesis of (R)-phenylalanine and non-natural (R)-phenylalanine derivatives (4-OH, 4-F, 3-F, and 2-F-Phe) by dynamic kinetic resolution (DKR). Recombinant E. coli with DaaA and mutant ACL racemase genes catalyzed the synthesis of (R)-phenylalanine with 84% yield and 99% ee from (RS)-phenylalaninamide (400 mM) in 22 h. (R)-Tyrosine and 4-fluoro-(R)-phenylalanine were also efficiently synthesized from the corresponding amide compounds. We also co-expresed two genes encoding mutant ACL racemase and L-amino acid amidase from Brevundimonas diminuta in E. coli and performed the efficient production of various (S)-phenylalanine derivatives. Moreover, 2-aminophenylpropionitrile was converted to (R)-phenylalanine by DKR using a combination of the non-stereoselective nitrile hydratase from recombinamt E. coli and mutant ACL racemase and DaaA from E. coli encoding mutant ACL racemase and DaaA genes. Copyright
