Overview
N-tert-Butoxycarbonyl-4-ketoproline (Boc-4-ketoproline) is a specialized amino acid derivative used primarily in peptide synthesis and medicinal chemistry. The tert-butoxycarbonyl (Boc) group protects the amine functionality during peptide chain assembly, while the 4-keto modification introduces reactivity for further derivatization. This compound is particularly valuable in solid-phase peptide synthesis (SPPS) and the development of constrained peptides, where the rigid proline backbone and ketone group enable unique structural conformations. As a non-natural proline analog, Boc-4-ketoproline serves as a building block for peptidomimetics and bioactive compounds. Its applications span drug discovery, especially in targeting protein-protein interactions, where modified proline residues can enhance binding affinity or metabolic stability. The compound is typically supplied as a crystalline powder with high purity (≥95%) for laboratory and industrial use.
Physical and Chemical Properties
Boc-4-ketoproline exhibits typical properties of Boc-protected amino acids, including moderate solubility in polar organic solvents like dimethylformamide (DMF) and dichloromethane (DCM). The ketone group at the 4-position of the proline ring introduces polarity and reactivity, enabling oxime or hydrazone formation for conjugation. The chiral center at C2 ensures optical activity, requiring stereospecific handling in asymmetric synthesis. Thermal stability is limited by the Boc group, which cleaves under acidic conditions (e.g., trifluoroacetic acid). The compound’s melting point (~85–90°C) is lower than unmodified proline due to the keto substitution. Spectroscopic characterization includes distinctive IR carbonyl stretches (Boc: ~1700 cm−1; ketone: ~1725 cm−1) and 1H NMR signals for the tert-butyl group (δ ~1.4 ppm).
Main Applications
In peptide synthesis, Boc-4-ketoproline acts as a constrained scaffold to introduce conformational rigidity or serve as a handle for bioconjugation. The ketone group allows post-synthetic modifications via oxime ligation or reductive amination, enabling linker attachment or fluorescent labeling. Pharmaceutical researchers leverage this to create peptide-drug conjugates or probes for target engagement studies. The compound is also pivotal in designing kinase inhibitors and GPCR ligands, where the 4-keto proline motif mimics phosphorylated residues or stabilizes beta-turn structures. Recent studies explore its use in macrocyclic peptides for undruggable targets like RAS oncoproteins. Industrial-scale applications include the production of custom peptides for diagnostic kits and APIs requiring controlled release profiles.
Safety and Storage
Boc-4-ketoproline requires standard precautions for laboratory chemicals. Use fume hoods to avoid dust inhalation, and wear nitrile gloves and safety goggles to prevent skin/eye contact. Though not highly toxic, prolonged exposure may cause irritation or sensitization. Spills should be contained with absorbent materials and disposed of as hazardous waste. Storage demands protection from moisture (hygroscopic) and light to prevent degradation. Ideal conditions are 2–8°C in sealed containers under inert gas (argon or nitrogen). Shelf life typically exceeds 2 years when stored properly. For transport, classify as non-dangerous goods under most regulations, but verify SDS for regional specifics.
B2B Procurement Guide
Bulk purchasers should prioritize suppliers with ISO-certified manufacturing and batch-specific Certificates of Analysis (CoA). Key specifications include HPLC purity (≥95% for research, ≥98% for GMP applications), enantiomeric excess (≥99% for chiral synthesis), and residual solvent levels (e.g., DMF <500 ppm). Pricing tiers depend on quantity: gram-scale orders cost $50–200/g, while kilogram purchases may drop to $10–50/g. Lead times vary; custom synthesis (e.g., isotopic labeling) requires 4–8 weeks. Preferred vendors include peptide specialty manufacturers (e.g., Bachem, GL Biochem) or agrochemical suppliers with peptide divisions. Request samples for QC validation before large orders.
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