Synthesis of 1,​1-​dioxobenzob​thiophene-​2-​ylmethyloxycarbonyl (Bsmoc) protected N-​methyl amino acids by reduction of Bsmoc-​5-​oxazolidinones and their use in peptide synthesis

摘要

The synthesis of Bsmoc-​N-​Me amino acids is presented. The first step involves p-​toluenesulfonic acid (TsOH) catalyzed condensation of a Bsmoc-​amino acid with paraformaldehyde to furnish N-​Bsmoc-​5-​oxazolidinone under MW irradn. This intermediate is reduced to the corresponding N-​Me amino acid using triethylsilane (Et3SiH) and trifluoroacetic acid (TFA) at room temp. The N-​Me amino acids are converted into corresponding acid fluorides using diethylaminosulfur trifluoride (DAST) and employed as coupling agents in the synthesis of dipeptides. The peptide coupling was mediated by KOAt in CH2Cl2.