Adapting the Glaser Reaction for Bioconjugation: Robust Access to Structurally Simple, Rigid Linkers

Abstract

The copper-mediated coupling between alkynes to generate a structurally rigid, linear 1,3-diyne linkage has been known for over a century. However, the mechanistic requirement to simultaneously maintain Cu(I) and an oxidant has limited its practical utility, especially for complex functional molecules in aqueous solution. We find that addition of a specific bpy-diol ligand protects unprotected peptides from Cu(II) mediated oxidative damage through formation of an insoluble Cu(II) gel which solves the critical challenge of applying the Glaser coupling to substrates that are degraded by Cu(II). The generality of this method is illustrated through conjugation of a series of polar and nonpolar labels onto a fully unprotected GLP-1R agonist through a linear 7 Å diynyl linker.

Rigid Peptide Macrocycles from On‐Resin Glaser Stapling

“…BCL9 is a transcriptional activator of β‐catenin, which is a primary mediator of the Wnt signaling pathway whose runaway activation is a hallmark of a number of human cancers, including colon cancer, prostate cancer, and melanoma . Inspired by recent work on the adaptation of the classic Glaser reaction for diyne formation in aqueous systems, we employed the BCL9 24‐mer peptide as a model system to develop a robust platform for peptide stapling by using inexpensive or easily synthesized amino acid building blocks, cheap catalysts and ligands, and mild reaction conditions capable of robust performance on a solid support.…”

Syntheses of Atypically Fluorinated Peptidyl Macrocycles through Sequential Vinylic Substitutions

“…l-Cbz-Ser-NH 2 reacted more slowly.M oreover,i nitially formed substitution product 11 c was unstable and reacted further in situ via its carboxamide, displacing an allylic fluoride through 6-exo trig cyclization to afford spirooxazinones 11 a/b (d.r = 1:1). Products 8-10 and 11 a/b were stable to handling and chromatography and showed diagnostic 19 FNMR spectra consistent with their assigned structures (see the Supporting Information).…”

“…Starting with the tyramide derivative of l ‐AF ( 12 , Scheme ), N‐acylation with 4‐pentynoic acid and exposure of the product to 6 in the presence of Cs 2 CO 3 (DMF, rt) gave diyne 13 as a white solid. Subjecting this material to Verniest's conditions for Glaser–Hay coupling afforded aryloxy hexafluorocyclopentene containing macrocyclic diyne 14 . We then tested whether vinylic substitution could be applied as the ring‐closing step.…”

“…Both structures were stable oils that could be purified by chromatography.S tarting with the tyramide derivative of l-AF (12,Scheme 2), N-acylation with 4-pentynoic acid and exposure of the product to 6 in the presence of Cs 2 CO 3 (DMF,rt) gave diyne 13 as awhite solid. Subjecting this material to Verniestsc onditions for Glaser-Hay coupling [18,19] afforded aryloxy hexafluorocyclopentene containing macrocyclic diyne 14.W et hen tested whether vinylic substitution could be applied as the ring-closing step. Acylation of 12 with 7 and treating the product with Cs 2 CO 3 (1.5 equiv,DMF,08 8C!rt) gave fluorinated macrocycle 16 in good overall yield.…”

The 1,3‐diyne linker as a rigid “i,i+7” staple for α‐helix stabilization: Stereochemistry at work

“…11 In recent years, several studies report the use of 1,3-diynes, obtained through Glaser-Hay alkyne-alkyne coupling, for both peptide secondary structure stabilization and biorthogonal labeling. [25][26][27][28][29][30]…”