Synthesis of Casein-Related Peptides and Phosphopeptides. III. The Unexpected Dephosphorylative Rearrangement of the Simple Model Phosphopeptides Ac-Ser(PO₃Bzl₂)-NHMe and Ac-Ser(Po₃H₂)-NHMe

Abstract

The simple phosphopeptide, Ac-Ser(PO₃Bzl₂)-NHMe , was found to be subject to a dephosphorylative rearrangement and gave H-Ser-NHMe .( BzlO )₂PO₂H after 12 months at 20°C. This dephosphorylative rearrangement process is proposed to proceed by an O to N phosphorus shift followed by acid hydrolysis of the N-acetyl group. Alternatively, the simple phospho-peptide, Ac-Ser(PO₃H₂)-NHMe, was found to undergo conversion into H-Ser- NHMe.H₃PO₄ over a period of four years, this process being established by a ¹³C n.m.r. spectroscopy study to proceed through initial acid hydrolysis of the N-acetyl group followed by phosphate loss.