title: Synthesis of an O-acyl isopeptide by using native chemical ligation in an aqueous solvent system.
abstract: O-Acyl isopeptides, in which the N-acyl linkage on the hydroxyamino acid residue (e.g. Ser and Thr) is replaced by an O-acyl linkage, generally suppress unfavorable aggregation properties derived from the corresponding parent peptides. Here, we report the synthesis of an O-acyl isopeptide of 34-mer pyroGlu-ADan (2), a component of amyloid deposits in hereditary familial Danish dementia, by using native chemical ligation. Native chemical ligation of pyroGlu(1) -ADan(1-21)-SCH2 CH2 SO3 (-) Na(+) (3) and Cys(22) -O-acyl isopeptide (4), in which the amino group of the Ser(29) residue at the isopeptide moiety was protected by an allyloxycarbonyl group, proceeded well in an aqueous solvent to yield a ligated O-acyl isopeptide (5). Subsequent disulfide bond formation and deprotection of the allyloxycarbonyl group followed by HPLC purification gave 2 with a reasonable overall yield. 2 was converted to the parent peptide 1 via an O-to-N acyl migration reaction. The sequential method, namely (i) native chemical ligation of the O-acyl isopeptide, (ii) HPLC purification as the O-acyl isopeptide form, and (iii) O-to-N acyl migration into the desired polypeptide, would be helpful to solve problems with HPLC purification of hydrophobic polypeptides in the process of chemical protein synthesis.
authors.affiliation: Department of Medicinal Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto, 607-8412, Japan; Department of Pharmaceutical Manufacturing Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto, 607-412, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kawashima
authors.forename: Tomomi
authors.initials: T
authors.lastname: Kuruma
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yamashita
authors.forename: Youhei
authors.initials: Y
authors.lastname: Sohma
authors.forename: Kenichi
authors.initials: K
authors.lastname: Akaji
mesh_terms: D002851:Chromatography, High Pressure Liquid; D057927:Hydrophobic and Hydrophilic Interactions; D008968:Molecular Conformation; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry / Q000302:isolation & purification; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000302:isolation & purification; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D009842:Oligopeptides; D010455:Peptides; D012997:Solvents; D014867:Water
keywords: HPLC; O-acyl isopeptide; O-to-N acyl migration; aggregation; amyloid; chemical protein synthesis; native chemical ligation; purification