<unk>  is a hybrid peptide design of the E.coli heat-stable enterotoxin (STa) and the endogenous peptide hormones endogenous guanylin and uroguanylin. It is a synthetic tetradecapeptide (14 amino acid peptide) with the sequence CCEYCCNPACTGCY by one-letter abbreviation, or by three-letter abbreviation: H–Cys1–Cys2–Glu3–Tyr4–Cys5–Cys6–Asn7–Pro8–Ala9–Cys10–Thr11–Gly12–Cys13–Tyr14–OH However, the actual structure of<unk>  is not fully specified without the three disulfide (R-S-S-R) bonds it contains, which are between Cys1 and Cys6, between Cys2 and Cys10, and between Cys5 and Cys13; these are shown in exaggerated fashion in the line-angle graphic showing the chemical bonds within and between each amino acid (and their stereochemistries, see the infobox, above right), and are represented using a one-letter abbreviations in the following additional schematic: center A study in discovery synthesis reported that 2 of 14 strategies available to synthesize<unk>  were successful—the successful ones involving trityl protection of all cysteines, or trityl protection of all cysteines except Cys1 and Cys6, which were protected with tert-butylsulphenyl groups. The study also reported that solution-phase oxidation (disulfide formation) was advisable over solid-supported synthesis for<unk> , and that the Cys1–Cys6 disulfide bridge was the most favored energetically.
Linaclotide
Pramlintide
Glibenclamide
Linagliptin
Insulin degludec
Exenatide
Lixisenatide
Saxagliptin