Synthesis of Fmoc-Thr Unit Carrying Core 1O-Linked Sugar With Acid-SensitiveO-Protecting Group and Its Application to the Synthesis of Glycosylated Peptide Thioester

Abstract

Y. Asahina et al.We newly designed and synthesized a 9-fluorenylmethoxycarbonyl (Fmoc)-threonine unit carrying the core 1 O-glycan, which is protected by the 4-methylbenzyl (MBn) group. This protection tactic enabled not only efficient assembly of glycoamino acid derivatives but also one-step deprotection by trifluoroacetic acid (TFA) after the Fmocsolid-phase peptide synthesis (SPPS). The usefulness of this unit was demonstrated by the Fmoc-SPPS of peptide thioester using the N-alkylcysteine (NAC)-assisted thioesterification method. The human interleukin-2 (1-27) sequence was assembled on the NAC resin and the obtained resin was treated with TFA containing cation scavengers to achieve one-step deprotection. The crude peptide was then thioesterified by reacting with an arylthiol to successfully obtain the desired peptide thioester carrying the core 1 O-glycan.

Chemical Synthesis of O‐Glycosylated Human Interleukin‐2 by the Reverse Polarity Protection Strategy

“…As a result, the reaction efficiently proceeded within four days (see Figure SI7 in the Supporting Information) and the desired peptide thioester 4 was obtained in 18 % yield based on the initial resin. The N‐terminal aryl thioester (1‐27) carrying the disaccharide 5 was synthesized using the NAC method as previously reported16 in a yield of 11 % (see Scheme SI4 and Figure SI8 in the Supporting Information).…”

Sialyl Tn Unit with TFA‐Labile Protection Realizes Efficient Synthesis of Sialyl Glycoprotein

“…We have recently demonstrated that the use of substituted‐benzyl protecting groups, instead of the Bn group, achieves a one‐step deprotection at the end of the SPPS, eliminating the problem of the low‐TfOH treatment . In particular, 4‐methylbenzyl (MBn) group is stable enough to the conditions required for the assembly of oligosaccharides, but sensitive to acid for the final deprotection using a TFA cocktail ,. Based on these results, we examined the extension of the MBn protection strategy for the carboxy‐ and hydroxy‐protection of sialic acid.…”

“…Based on previous results,, we first attempted the use of the MBn group as a protecting group for both the hydroxy and carboxy groups of sialic acid. The synthesis of sialylglycoamino acid 1 is shown in Scheme .…”

Chemical Synthesis of O‐Glycosylated Human Interleukin‐2 by the Reverse Polarity Protection Strategy

“…Thecarboxylic acid seems to participate in the N-to-S acyl shift reaction and enhance the overall rate of thioesterification reaction. TheN-terminal aryl thioester (1-27) carrying the disaccharide 5 was synthesized using the NACm ethod as previously reported [16] in ayield of 11 %(see Scheme SI4 and Figure SI8 in the Supporting Information). As aresult, the desired peptide thioester with MESNa was successfully obtained (see Figure SI6 in the Supporting Information).…”

“…As ar esult, the reaction efficiently proceeded within four days (see Figure SI7 in the Supporting Information) and the desired peptide thioester 4 was obtained in 18 %y ield based on the initial resin. TheN-terminal aryl thioester (1-27) carrying the disaccharide 5 was synthesized using the NACm ethod as previously reported [16] in ayield of 11 %(see Scheme SI4 and Figure SI8 in the Supporting Information). Scheme 1.…”