Extended diethylglycine homopeptides formed by desulfurization of their tetrahydrothiopyran analogues

Diethylglycine (Deg) homopeptides adopt the rare 2.0(5)-helical conformation, the longest three-dimensional structure that a peptide of a given sequence can adopt. Despite this unique conformational feature, Deg is rarely used in peptide design because of its poor reactivity. In this paper, we show that reductive desulfurization of oligomers formed from more reactive tetrahydrothiopyran-containing precursors provides a practical way to build the longest Deg homopeptides so far made, and we detail some conformational studies of the Deg oligomers and their heterocyclic precursors.