In S-acylcysteines and homocysteines, the efficacy and rate of S→N-acyl transfer (5 and 6 cyclic TSs) vary with the size of S-acyl group. Conformational and quantum chemical calculations indicate that the spatial distance, b(N-C), between the terminal amine and the thioester carbon is shortened by α-C(O)X (X = OH, OMe, NH2 ) substituents.
Poly(2, phenylene vinylene) (BAM-PPV) has been studied for several decades as an anti-corrosion coating. Although the polymer is readily synthesized via base-promoted radical chain polymerization, BAM-PPV exhibits poor solubility at high-molecular weights (M w > 100 kDa), which limits its applications. In this work, the molecular weight of BAM-PPV was modulated with nitrobenzene. At nitrobenzene loading as low as 0.9 mol %, the polymerization reaction produced low-molecular weight BAM-PPV (M w = 5-46 kDa). The polymerization of BAM-PPV was systematically studied via size-exclusion chromatography (SEC), liquid chromatography-mass spectrometry (LC-MS), and 1 H NMR spectroscopy, which revealed suppression of the dimer intermediate before chain polymerization. Collectively, this work could expand the practical applications of BAM-PPV for use in optoelectronic devices or corrosion inhibition coatings.
Non-Phosgene Route to Unsymmetrical Ureas from N-Cbz-α-Amino AcidAmides. -A convenient method toward the synthesis of α-amino acid-derived unsymmetrical ureas (II) is described. This route involves an interesting rearrangement of amides of N-Cbz-α-amino acids, which presumably entails the intermediacy of hydantoins that is followed by hydrolysis to afford unsymmetrical ureas in quantitative yields and high purity. -(ZADEH*, E. H. G.; ABO-DYA, N. E.; SOTUYO, A. C.; GHIVIRIGA, I.; HALL, C. D.; Tetrahedron Lett. 54 (2013) 40, 5467-5469, http://dx.
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