“…1,2,3triazoles, [143] thiazole, [112] or 1,3,4-oxadiazoles [144] and thus increases peptide rigidity iii)used for backbone cyclization, e.g. 1,2,3-triazoles, [145] 1,3,4-oxadiazoles, [144] thiazoles, [146] or thiazolidines [146b] iv) sanguinamid Aa nd danamide F(F= 51 AE 9%)d erived from it, are the most prominent examples [112] v) many reviews dealing with heterocycle-containing peptides have been recently published [142,147] [142, 144, 147b] cyclic alanine i) known as Freidinger lactam [148] in combination with R 1 = Leu, a b-turn mimetic in acyclic peptide ii)possesses the same trans-dominated equilibriumast he standard peptide bond in contrast with N-methylation or Pro iii)removal of hydrogen bond donor iv) increasess erum stability and cell permeability [149] v) its effect on bioavailability has not been systematicallys tudied [148,149] a-methylation i) a-methylation marginally increasesthe entire lipophilicity of peptides ii)rarely used [150] iii)present three times in ZYGO1 (20), alinear orally available GLP-1 antagonist [151] [150]…”