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.
J Pept Sci. 2014 May;20(5):361-5. doi: 10.1002/psc.2622. Epub 2014 Mar 4.
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.
O-酰基异肽中，羟氨基酸酸残基（如 Ser 和 Thr）上的 N-酰基连接被 O-酰基连接取代，通常会抑制源自相应母体肽的不利聚集特性。在这里，我们通过使用天然化学连接报告了 34 个残基焦谷氨酸-ADan（2）的 O-酰基异肽的合成，焦谷氨酸-ADan（2）是遗传性丹麦家族性痴呆症中淀粉样沉积物的成分之一。焦谷氨酸（1）-ADan（1-21）-SCH2 CH2 SO3（-）Na（+）（3）和 Cys（22）-O-酰基异肽（4）的天然化学连接，其中异肽部分 Ser（29）残基的氨基被烯丙氧羰基保护，在水溶剂中反应良好，生成连接的 O-酰基异肽（5）。随后进行二硫键形成和烯丙氧羰基的去保护，再通过 HPLC 纯化得到具有合理总产率的 2。2 通过 O 到 N 酰基迁移反应转化为母体肽 1。该顺序方法，即（i）O-酰基异肽的天然化学连接，（ii）HPLC 纯化作为 O-酰基异肽形式，和（iii）O 到 N 酰基迁移到所需的多肽中，将有助于解决化学蛋白质合成过程中疏水性多肽的 HPLC 纯化问题。
