RESUMO
A new and efficient synthesis of (L)-(trimethylsilyl)alanine (TMSAla) with suitable protection for use in Solid Phase Peptide Synthesis (SPPS) has been accomplished starting from glycine tert-butyl ester and using hydroxypinanone as chiral inductor. The silylated side chain was introduced by alkylation of the Schiff base intermediate with iodomethyl(trimethylsilane) at -78 °C. Among the different synthetic routes that were tested including several chiral inductors and different Schiff bases, this strategy was selected and afforded (L)-TMSAla in good chemical overall yield with 98 % ee.
Assuntos
Alanina/análogos & derivados , Compostos de Trimetilsilil/síntese química , Alanina/síntese química , Alquilação , Catálise , Glicina/análogos & derivados , Glicina/química , Estrutura Molecular , Bases de Schiff/química , EstereoisomerismoRESUMO
Silaproline is an analogue of proline, which exhibits similar conformational properties. Moreover, the presence of dimethylsilyl group confers to silaproline a higher lipophilicity as well as an improved resistance to biodegradation. This report describes the comparison of two routes to obtain Fmoc-(L) Sip-OH on the gram scale using chiral HPLC resolution.
Assuntos
Aminoácidos/síntese química , Fluorenos/síntese química , Compostos de Organossilício/síntese química , Prolina/análogos & derivados , Aminoácidos/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Fluorenos/isolamento & purificação , Furanos/química , Glicina/química , Estrutura Molecular , Compostos de Organossilício/química , Compostos de Organossilício/isolamento & purificação , Prolina/síntese química , Prolina/química , Prolina/isolamento & purificação , Solventes/química , EstereoisomerismoRESUMO
In the present study, we propose a general and accessible method for the resolution of enantiomeric 1,2-sn- and 2,3-sn-diacylglycerols based on derivatization by isocyanates, which can be easily used routinely by biochemists to evaluate the stereopreferences of lipases in a time course of triacylglycerol (TAG) hydrolysis. Diacylglycerol (DAG) enantiomers were transformed into carbamates using achiral and commercially available reagents. Excellent separation and resolution factors were obtained for diacylglycerols present in lipolysis reaction mixtures. This analytical method was then applied to investigate the stereoselectivity of three model lipases (porcine pancreatic lipase, PPL; lipase from Rhizomucor miehei, MML; and recombinant dog gastric lipase, rDGL) in the time course of hydrolysis of prochiral triolein as a substrate. From the measurements of the diglyceride enantiomeric excess it was confirmed that PPL was not stereospecific (position sn-1 vs sn-3 of triolein), whereas MML and rDGL preferentially hydrolyzed the ester bond at position sn-1 and sn-3, respectively. The enantiomeric excess of DAGs was not constant with time, decreasing with the course of hydrolysis. This was due to the fact that DAGs can be products of the stereospecific hydrolysis of TAGs and substrates for stereospecific hydrolysis into monoacylglycerols.
