Fully Synthetic Granulocyte Colony-Stimulating Factor Enabled by Isonitrile-Mediated Coupling of Large, Side-Chain-Unprotected Peptides

• Published in: Journal of the American Chemical Society Vol. 137; no. 40; pp. 13167 - 13175
• Main Authors: Roberts, Andrew G, Johnston, Eric V, Shieh, Jae-Hung, Sondey, Joseph P, Hendrickson, Ronald C, Moore, Malcolm A. S, Danishefsky, Samuel J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14.10.2015
• Subjects: Amino Acid Sequence; drug therapy; Electrophoresis, Polyacrylamide Gel; glycoproteins; glycosylation; granulocyte colony-stimulating factor; Granulocyte Colony-Stimulating Factor - chemistry; hematopoiesis; humans; Molecular Sequence Data; neutropenia; patients; Peptides - chemistry
• ISSN: 0002-7863; 1520-5126; 1520-5126
• DOI: 10.1021/jacs.5b08754

Human granulocyte colony-stimulating factor (G-CSF) is an endogenous glycoprotein involved in hematopoiesis. Natively glycosylated and nonglycosylated recombinant forms, lenograstim and filgrastim, respectively, are used clinically to manage neutropenia in patients undergoing chemotherapeutic treatment. Despite their comparable therapeutic potential, the purpose of O-linked glycosylation at Thr133 remains a subject of controversy. In light of this, we have developed a synthetic platform to prepare G-CSF aglycone with the goal of enabling access to native and designed glycoforms with site-selectivity and glycan homogeneity. To address the synthesis of a relatively large, aggregation-prone sequence, we advanced an isonitrile-mediated ligation method. The chemoselective activation and coupling of C-terminal peptidyl Gly thioacids with the N-terminus of an unprotected peptide provide ligated peptides directly in a manner complementary to that with conventional native chemical ligation–desulfurization strategies. Herein, we describe the details and application of this method as it enabled the convergent total synthesis of G-CSF aglycone.