Fmoc-Gly-OSu

Fmoc-Gly-OSu is an N-(9H-fluoren-9-ylmethoxycarbonyl) protected glycine N-hydroxysuccinimyl ester that combines an Fmoc-protected amino group with a highly activated OSu leaving group on the carboxylate. The molecule is achiral due to the glycine backbone, yet it is structurally defined by the Fmoc carbamate and the succinimidyl ester functionality, which together govern its stability and coupling behavior. The OSu ester readily undergoes nucleophilic acyl substitution with amines under peptide synthesis conditions, while the Fmoc group provides orthogonal protection that can be removed to expose the amino terminus for iterative chain assembly. As a protected amino acid derivative, Fmoc-Gly-OSu functions as a reactive glycine building block for rapid peptide bond formation and as a downstream intermediate for generating glycine-containing conjugates and labeled or modified peptide fragments.

1. Peptide Coupling Reagents

Fmoc-Gly-OSu is used in peptide synthesis workflows as an activated glycine carboxylate for amide bond formation with appropriately protected amines. The OSu ester activates the glycine carbonyl toward acyl substitution, while the Fmoc-protected nitrogen maintains compatibility with orthogonal deprotection strategies during stepwise assembly. The activated ester can be employed to construct glycine-containing sequences where fast coupling and predictable amide formation are required, including short peptide fragments and longer chain elongation steps. The resulting peptide products retain the glycine residue's small side chain, supporting clean structural incorporation into peptide scaffolds and peptidomimetic precursors.

2. Protected Amino Acid Synthesis

Fmoc-Gly-OSu serves as a practical intermediate in protected amino acid chemistry and amino acid ester/activated ester handling for downstream derivatization. The Fmoc carbamate provides a stable N-protection handle that can be removed under base-promoted conditions to regenerate an Fmoc-free glycine amine for subsequent coupling cycles. The succinimidyl ester group enables controlled conversion into amide-linked derivatives without requiring direct use of free glycine carboxylic acid, which can simplify protection-state management in synthesis planning. The compound's defined protection pattern makes it suitable for preparing glycine building blocks that feed into automated peptide synthesis libraries and custom peptide analog construction.

3. Bioconjugation Linker Chemistry

Fmoc-Gly-OSu can be applied in chemical biology and bioconjugation contexts where glycine-derived amide linkages are formed between an activated carboxylate and nucleophilic amino groups on biomolecules or biomolecule-reactive partners. The OSu ester reacts with primary amines to install a glycinyl amide motif, while the Fmoc group can be used as a protected functional handle during synthetic sequencing or to control reactivity until deprotection is performed. The small glycine spacer can influence local conformational presentation in conjugates, supporting consistent linker geometry in labeled peptides, peptide-tagged constructs, and glycine-containing adapter molecules. The resulting amide-linked products can be further processed into peptide conjugates used for analytical detection, affinity reagent preparation, or scaffold generation for biomolecular interaction studies.

4. Solid-Phase Peptide Synthesis

Fmoc-Gly-OSu is suitable for solid-phase peptide synthesis and related peptide building block strategies where activated esters are coupled to resin-bound or protected amine-bearing intermediates. The Fmoc protection on the glycine nitrogen aligns with standard Fmoc/tBu-type orthogonal protection schemes, enabling iterative deprotection and coupling cycles with the glycine residue as a defined unit. The OSu ester functionality supports nucleophilic acyl substitution by the amine nucleophile generated after deprotection, facilitating incorporation of glycine at specific positions within a peptide sequence. The approach supports downstream formation of peptide libraries and sequence-defined constructs used in structure-activity relationship studies, peptide mapping, and method development for peptide assembly.

5. Analytical Reference Standards

Fmoc-Gly-OSu can be used as a synthetic reference material and derivatization reagent in analytical research that requires defined Fmoc-protected glycine species or glycine-containing amide products. The presence of the Fmoc group provides a distinctive fluorophore-tagged protecting motif that can assist in method development for monitoring deprotection/coupling events or confirming identity of glycine incorporation in peptide fragments. The OSu ester can also serve as a controlled precursor for generating glycinyl amide derivatives used to calibrate analytical workflows such as LC-MS identification of protected amino acid derivatives and peptide coupling intermediates. The compound's clear structural features make it useful for verifying synthetic intermediates and supporting quality-focused characterization of peptide-building steps in research-grade amino acid chemistry.

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