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.
Synthesis and biological evaluation of new active For-Met-Leu-Phe-OMe analogues containing para-substituted Phe residues
Mollica, Adriano,Feliciani, Federica,Stefanucci, Azzurra,Costante, Roberto,Lucente, Gino,Pinnen, Francesco,Notaristefano, Daniela,Spisani, Susanna
experimental part, p. 418 - 426 (2012/08/28)
In the present study, we report synthesis and biological evaluation of the N-Boc-protected tripeptides 4a-l and N-For protected tripeptides 5a-l as new For-Met-Leu-Phe-OMe (fMLF-OMe) analogues. All the new ligands are characterized by the C-terminal Phe residue variously substituted at position 4 of the aromatic ring. The agonism of 5a-l and the antagonism of 4a-l (chemotaxis, superoxide anion production, lysozyme release as well as receptor binding affinity) have been examined on human neutrophils. No synthesized compounds has higher activity than the standard fMLF-OMe tripeptide to stimulate chemotaxis, although compounds 5a and 5c with -CH3 and -C(CH3)3, respectively, in position 4 on the aromatic ring, are better than the standard tripeptide to stimulate the production of superoxide anion, in higher concentration. Compounds 4f and 4i, containing -F and -I in position 4, respectively, on the aromatic ring of phenylalanine, exhibit significant chemotactic antagonism. The influence of the different substitution at the position 4 on the aromatic ring of phenylalanine is discussed.