Inorganic Chemistry, Vol.53, No.19, 10602-10610, 2014
Peptide Coupling between Amino Acids and the Carboxylic Acid of a Functionalized Chlorido-gold(I)-phosphane
We have developed a protocol for the direct coupling between methyl ester protected amino acids and the chlorido-gold(I)-phosphane (p-HOOC(C6H4)PPh2)AuCl. By applying the EDC center dot HCl/NHS strategy (EDC center dot HCl = N-ethyl-N'-(3-(dimethylamino)propyl)carbodiimide hydrochloride, NHS = N-hydroxysuccinimide), the methyl esters of L-phenylalanine, glycine, L-leucine, L-alanine, and L-methionine are coupled with the carboxylic acid of the gold complex in moderate to good yields (62-88%). All amino acid tagged gold complexes were characterized by H-1 and C-13 NMR spectroscopy and high-resolution mass spectrometry. As corroborated by measurement of the angle of optical rotation, no racemization occurred during the reaction. The molecular structure of the leucine derivative was determined by single-crystal X-ray diffraction. In the course of developing an efficient coupling protocol, the acyl chlorides (p-Cl)(O)C(C6H4)PPh2)AuX (X = Cl, Br) were also prepared and characterized.