A General Reaction of Amino Acids. Ii

Homogeneous and heterogeneous catalysts for multicomponent reactions

“…[293][294] Moreover they are important synthons for a variety of speciality chemicals 295 and pharmaceuticals such as nikkomycine and neopolyxine antibiotics. 296 The main route for the synthesis of these compounds is the Dakin-West reaction 297 which involves the condensation of an a-aminoacid with acetic anhydride in the presence of a base via an intermediate azalactone. Recently Bathia et al 298 have proposed another general route for the synthesis of b-acetamido ketones that involves the condensation of an aryl aldehyde, an enolizable ketone or ketoester, acetyl chloride and acetonitrile in the presence of Lewis acid catalysts such as CoCl 2 (Scheme 56).The same author performed this MCR using Montmorillonite K10 as the acid catalyst.…”

On the mechanism of the Dakin–West reaction

“…1,2 After the discovery of the Dakin-West reaction, and the observation of its complex structural rearrangements, efforts were undertaken to elucidate its reaction mechanism, and several alternatives have been proposed. 8 The currently accepted "azlactone" pathway still follows the originally proposed mechanism by Dakin and West 9 and was subsequently corroborated by Allinger and coworkers (Scheme 2). 8 In this mechanistic proposal, the synthesis of the α-acetamido ketone starts with the formation of the mixed anhydride 3 from the α-amino acid (1) or its N-acyl derivative (2).…”

Biobased Pyrazine-Containing Polyesters

“…Under such conditions, however, a stoichiometric amount of diol was found to be too small for dissolution of the diacid upon melting of the diol. Since DMDPP does not show a melting point and degrades at 211−213 °C, 13,14 further heating of the reaction until the diacid would melt was not a viable synthesis approach. This limitation was circumvented by synthesis of the dimethyl ester of DMDPP, which has a stable melt at 96−98 °C, allowing polymerization via transesterification.…”

“…1 H NMR (300 MHz, CDCl 3 ) δ (ppm) = 4.00 (t, J = 6.7 Hz, 4H), 2.96 (t, J = 7.3 Hz, 4H), 2.71 (t, J = 7.3 Hz, 4H), 2.41 (s, 6H), 1.63−1.48 (m, 4H), 1.36−1.24 (m, 4H). 13 C NMR (75 MHz, CDCl 3 ) δ (ppm) = 173.4, 149.4, 148.0, 64.4, 31.7, 28.5, 25.6, 20.9. IR (ATR) ν̃(cm −1 ) = 2939, (w), 1730 (vs), 1420 (m), 1364 (m), 1297, (m) 1176 (s), 1132 (s), 970 (vs), 785 (m), 672 (w).…”

“…Measurements were run in chloroform-d using 5−10 mg of polymer. The 1 H NMR (300 MHz) spectra were recorded with 16 scans, and the 13 C NMR (75 MHz) APT spectra were recorded at 1024 scans. The obtained NMR data was used to determine the conversion of the end-groups and the degree of polymerization.…”