Boc-L-aspartic acid β-methyl ester CAS 2018-61-3 98% white crystalline powder Boc-protected amino acid / peptide synthesis intermediate

1. Product Overview

Boc-L-aspartic acid β-methyl ester (also known as Boc-Asp(OMe)-OH or N-(tert-Butoxycarbonyl)-L-aspartic acid 4-methyl ester) is a derivative of the natural amino acid L-aspartic acid, in which the α-amino group is protected by a tert-butoxycarbonyl (Boc) group and the β-carboxyl group is esterified with a methyl group. With the molecular formula C₁₀H₁₇NO₆ and CAS number 2018-61-3, this compound appears as a white to off-white crystalline powder. It is a widely used building block in peptide synthesis, offering orthogonal protection strategies where the α-carboxyl remains free for activation while the side-chain carboxyl is selectively masked as a methyl ester. The Boc group can be readily removed under mild acidic conditions (e.g., TFA/DCM), making it highly compatible with standard peptide coupling protocols. The product is supplied at ≥98% purity (HPLC), suitable for pharmaceutical intermediate, peptide API synthesis, and custom research applications.

2. Key Features and Advantages

• High chiral purity with defined L-configuration, ensuring stereoselectivity in peptide coupling and asymmetric synthesis.

• Orthogonal dual protection: Boc on α-NH₂ and methyl ester on β-COOH, leaving α-COOH free for activation and coupling.

• Mild and selective Boc deprotection under acidic conditions (TFA, HCl/dioxane) without affecting the methyl ester or peptide backbone.

• Excellent compatibility with Fmoc chemistry in multi-step peptide assembly and solid-phase peptide synthesis (SPPS).

• Consistent crystallinity and low moisture content, ensuring reliable weighing and reproducible reaction performance.

• Stable under recommended storage conditions with excellent batch-to-batch reproducibility.

3. Main Applications

• Peptide synthesis: serves as a key protected Asp building block for introducing aspartic acid residues with selective side-chain protection in both SPPS and solution-phase peptide synthesis.

• Pharmaceutical intermediate: used in the manufacture of peptide-based active pharmaceutical ingredients (APIs), GLP-1 analogs, oxytocin derivatives, and other bioactive peptides.

• Combinatorial chemistry: employed in library synthesis where orthogonal amino and side-chain carboxyl protection is required.

• Bioconjugation and PROTAC synthesis: acts as a chiral linker or spacer component in proteolysis-targeting chimeras and antibody-drug conjugates (ADCs).

• Fine chemical manufacturing: used in the custom synthesis of modified peptides, peptidomimetics, and specialty organic intermediates.

4. Technical Specifications

5. Storage and Handling

Store in a cool, dry, well-ventilated area at 2–8 °C in a tightly sealed container, protected from moisture and light. For long-term storage (over 12 months), keep at −20 °C under inert atmosphere (N₂ or Ar) to prevent hydrolysis of the ester group. Keep container tightly closed when not in use. Avoid exposure to strong acids, strong bases, and strong oxidizing agents. Handle in a well-ventilated area using appropriate personal protective equipment (lab coat, nitrile gloves, safety goggles). Minimize dust generation during weighing; use a fume hood if aerosol formation is possible. Do not eat, drink, or smoke in handling areas. Wash hands thoroughly after use.

6. Safety Overview

This substance is classified under GHS as Warning (GHS07 pictogram). Hazard statements: H315 (Causes skin irritation), H319 (Causes serious eye irritation), H335 (May cause respiratory irritation). Precautionary statements include P261 (Avoid breathing dust/fume), P264 (Wash skin thoroughly after handling), P271 (Use only outdoors or in well-ventilated area), P280 (Wear protective gloves/eye protection), P305+P351+P338 (IF IN EYES: Rinse cautiously with water for several minutes; remove contact lenses if present and easy to do; continue rinsing). In case of inhalation, move to fresh air; if irritation persists, seek medical attention. For skin contact, wash with plenty of soap and water. For eye contact, irrigate immediately with copious water for at least 15 minutes. Not intended for human or veterinary therapeutic use; for laboratory and industrial research purposes only. WGK Germany: 3. Transport: not classified as dangerous goods under UN model regulations (NONH for all modes). Consult the full SDS before use.