Gobbo M, Biondi L, Filira F, Rocchi R
C.N.R., Department of Organic Chemistry, University of Padova, Italy.
Int J Pept Protein Res. 1991 Nov;38(5):417-27. doi: 10.1111/j.1399-3011.1991.tb01522.x.
The glyco-hexapeptide sequence H-Val-(GalNAc-alpha)Thr-His-Pro-Gly-Tyr-OH, was synthesized in solution by the segment condensation procedure and the stepwise procedure. A peracetylated, O-galactosaminyl threonine derivative was used for incorporating the glycosylated amino acid residue into the peptide chain. A consistent racemization occurred during the acylation of H-His-Pro-Gly-Tyr(Bzl)-OBzl with Z-Val-[GalNAc(Ac)3-alpha]Thr-OH by the BOP-HOBt procedure and the D-allothreonine containing glyco-hexapeptide was isolated in about 20% yield. Stepwise elongation of the C-terminal tetrapeptide with Fmoc-[GalNAc(Ac)3-alpha]Thr-OH and Z-Val-OH, in the presence of the same coupling reagents, yielded the L-threonine containing diastereoisomer without detectable racemization. A side product, the Nim-ethoxycarbonylated hexapeptide derivative, formed during the EEDQ-mediated condensation of Fmoc-[GalNAc(Ac)3-alpha]Thr-OH with the C-terminal tetrapeptide, was isolated and characterized. Preliminary studies showed that the synthetic glycohexapeptide is a good competitive inhibitor of the binding of the FDC-6 monoclonal antibody to the oncofetal fibronectin, supporting the idea that it should represent the minimum essential structure required for the FDC-6 activity.
通过片段缩合程序和逐步合成程序在溶液中合成了糖基化六肽序列H-Val-(GalNAc-α)Thr-His-Pro-Gly-Tyr-OH。使用全乙酰化的O-半乳糖胺基苏氨酸衍生物将糖基化氨基酸残基掺入肽链中。在通过BOP-HOBt程序用Z-Val-[GalNAc(Ac)3-α]Thr-OH对H-His-Pro-Gly-Tyr(Bzl)-OBzl进行酰化反应过程中发生了一致的消旋化，并且以约20%的产率分离出了含D-别苏氨酸的糖基化六肽。在相同的偶联试剂存在下，用Fmoc-[GalNAc(Ac)3-α]Thr-OH和Z-Val-OH对C端四肽进行逐步延伸，得到了不含可检测到的消旋化的含L-苏氨酸的非对映异构体。在Fmoc-[GalNAc(Ac)3-α]Thr-OH与C端四肽的EEDQ介导的缩合反应过程中形成的副产物Nim-乙氧羰基化六肽衍生物被分离并进行了表征。初步研究表明，合成的糖基化六肽是FDC-6单克隆抗体与癌胚纤连蛋白结合的良好竞争性抑制剂，这支持了它应代表FDC-6活性所需的最小基本结构的观点。
