| HS Code | 451588 |
| Product Name | BOC-D-glutamic Acid |
| Chemical Name | N-(tert-Butoxycarbonyl)-D-glutamic acid |
| Cas Number | 34459-67-1 |
| Molecular Formula | C10H17NO6 |
| Molecular Weight | 247.25 g/mol |
| Appearance | White to off-white powder |
| Purity | ≥98% |
| Melting Point | 108-112°C |
| Solubility | Soluble in DMSO, methanol, ethanol; sparingly soluble in water |
| Storage Conditions | Store at 2-8°C, protected from moisture and light |
| Optical Rotation | +8.5° (c=1, AcOH) |
As an accredited BOC-D-glutamic Acid factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | BOC-D-glutamic acid, 5 g, supplied as a white powder in a sealed amber glass bottle with safety label and desiccant. |
| Container Loading (20′ FCL) | BOC-D-glutamic Acid packed in sealed drums, palletized, secured in 20′ FCL container for safe transport. |
| Shipping | BOC-D-glutamic acid ships as a solid in sealed, light-protected containers, stable at ambient temperature. Keep away from moisture and extreme heat. Ensure proper labeling per transport regulations; it is non-hazardous under normal conditions. Use gloves and work in a ventilated area during handling to avoid dust inhalation. |
| Storage | Store BOC-D-glutamic Acid in a tightly sealed container under dry, inert conditions, protected from light and moisture. Recommended storage is refrigerated or frozen, ideally at -20°C, to maintain stability. Keep away from heat, ignition sources, and incompatible materials. Allow to equilibrate to room temperature before opening to prevent condensation. |
| Shelf Life | Shelf life is typically 2–3 years when stored cool, dry, and tightly sealed, protected from moisture and light. |
BOC-D-glutamic acid (CAS 34404-28-9; C10H17NO6; 247.25 g/mol) is charged into a Boc-strategy solid-phase peptide synthesis campaign when a D-glutamic acid residue must be introduced at the N-terminus or at an internal position where the γ-carboxyl is required to remain free for binding, branching, or subsequent conjugation. The monomer is dissolved in pre-dried DMF with water content ≤50 ppm and activated with HBTU/HOBt/DIPEA at a molar ratio of 1.0:0.95:2.0 relative to BOC-D-Glu-OH; the solution is added to the resin at 1.2 equivalents per free amine equivalent. Coupling is performed on a 1% cross-linked chloromethylated polystyrene resin with a loading of 0.45–0.65 mmol/g in a recirculating batch synthesizer with nitrogen agitation at 20–25°C. The system is fitted with a fritted glass column and in-line UV monitoring; when the Kaiser test remains negative after 45–60 minutes, a capping solution of acetic anhydride/pyridine/DMF 1:1:8 is applied to block unreacted free amines. N-terminal Boc removal is performed with TFA/DCM 1:1 at 20–25°C for 30 minutes, followed by DMF washes. Final peptide cleavage from the resin and side-chain deprotection use HF/anisole 9:1 at 0–2°C for 60–90 minutes, after which the crude peptide is precipitated in cold diethyl ether and lyophilized with the shelf temperature held below -20°C to prevent pyroglutamyl artifact formation from the free D-Glu γ-carboxyl. Because the N-Boc group is not removed by piperidine, this route is incompatible with standard Fmoc/tBu SPPS and is selected only for Boc/Bn process design or solution-phase fragment condensation. Regulatory controls include ICH Q7 Section 7.4 for in-process monitoring, ICH Q3C(R8) for residual DMF and DCM, and 21 CFR 211.165(a) for finished drug substance release testing. Terminal output is a lyophilized therapeutic peptide API containing one or more D-glutamic acid residues, with batch sizes typically controlled by column diameter and resin loading in the 1–20 kg range for phase-appropriate cGMP manufacturing.
In solution-phase cGMP intermediate manufacturing, BOC-D-Glu-OH is converted to BOC-D-Glu(OBn)-OH to render the γ-carboxyl inert during subsequent α-carboxyl-selective coupling steps. The process charges 1.0 mol BOC-D-Glu-OH, 1.1 mol benzyl bromide, and 1.5 mol anhydrous potassium carbonate in 6 volumes of DMF. The dispersion is maintained at 0–5°C for the first 2 hours and then warmed to 20–25°C for 8–12 hours with slow agitation at 120 rpm. Completion is determined by reverse-phase HPLC on a C18 column, 150×4.6 mm, with detection at 210 nm; residual BOC-D-Glu-OH is specified at ≤0.5% area. The crude mixture is partitioned between ethyl acetate and 5% w/v aqueous citric acid, washed with 0.2 M sodium chloride, dried over sodium sulfate, and concentrated under vacuum at 25–30°C. Residual DMF is controlled to ICH Q3C(R8) Class 2 limits because the benzyl-protected intermediate feeds an injectable peptide API route, and elemental impurities are evaluated under ICH Q3D(R2). Chiral purity is confirmed by polarimetry at 589 nm using a 100 mm path length cell; optical rotation drift beyond ±2° from the validated reference value triggers an out-of-specification review under ICH Q7 Section 7.4. The terminal product is BOC-D-Glu(OBn)-OH, a protected chiral amino acid derivative used for selective α-carboxyl amide bond formation in solution-phase peptide fragment manufacture.
Parallel split-and-pool peptide library campaigns that replace L-Glu residues with D-Glu for proteolytic stability screening use BOC-D-Glu-OH as a protected building block in multiwell synthesizers rather than as a cGMP API intermediate. Each coupling well receives 4.0 equivalents of BOC-D-Glu-OH relative to resin free amine, activated with 3.8 equivalents of HATU and 8.0 equivalents of DIPEA in DMF. The resin is a TentaGel S NH2 support with nominal loading of 0.25 mmol/g; reaction volume per well is 0.8 mL, and mixing is performed by orbital shaking at 900 rpm for 45 minutes at 25°C. After each coupling, a capping solution of acetic anhydride/pyridine/DMF 1:1:8 blocks unreacted free amines. Boc removal uses TFA/DCM 1:1 for 30 minutes, and final side-chain deprotection and cleavage use TFA/TIS/H2O 95:2.5:2.5 for 120 minutes at 25°C. Because the D-Glu γ-carboxyl remains free, library members with this residue require LC/MS monitoring for pyroglutamyl artifacts when cleavage solutions are concentrated above 30°C during evaporation. Process controls are governed by ISO 9001:2015 Clause 8.5.1, and residual solvent levels are reported against ICH Q3C(R8) for analytical comparability even though the material is not intended for human use. Terminal products are crude peptide libraries at 5–20 mg per well containing D-Glu substitutions for ligand-binding and metabolic-stability screening.
Thermal cyclization of BOC-D-Glu-OH to BOC-D-pyroglutamic acid proceeds through intramolecular amidation between the γ-carboxyl and the N-H of the Boc-carbamate. The production charge uses 1.0 mol BOC-D-Glu-OH, 0.02 mol p-toluenesulfonic acid, and 5 volumes of methylcyclohexane in a glass-lined reactor equipped with a Dean-Stark trap and overhead stirring. The suspension is heated with a thermal oil jacket set to 110°C to maintain an internal temperature of 80°C for 6–8 hours, with water removal monitored until the distillate remains clear. Running below 80°C slows conversion and extends cycle time without improving chiral purity; temperatures above 85°C increase the risk of decarboxylation at the α-position and generate a colored impurity that co-elutes with the product on reverse-phase HPLC. The reaction mixture is cooled to 0–5°C, filtered, and washed with cold methylcyclohexane, then dried under vacuum at 35°C to ≤0.05% residual solvent. Chiral purity is measured by polarimetry at 589 nm and by chiral HPLC; acceptance is ≥98.0% area. Residual methylcyclohexane is controlled as a Class 2 solvent under ICH Q3C(R8), and elemental impurities are assessed using ICH Q3D(R2) because the material may be used as an intermediate for pharmaceutical routes. The terminal product is BOC-D-pyroglutamic acid, a protected chiral synthon for subsequent preparation of D-pyroglutamyl amides and peptidomimetic intermediates in CDMO processes.
For drug conjugate programs that require proteolytically stable D-configuration spacer arms, BOC-D-Glu-OH is first converted to an alpha-allyl-protected derivative because unprotected α-carboxyl groups cause branched ester/amide mixtures during γ-chain elongation. The alpha-allyl protection step uses 1.0 mol BOC-D-Glu-OH, 1.1 mol allyl bromide, and 1.2 mol DIPEA in DMF at 0–5°C for 4 hours. The resulting intermediate is then coupled iteratively to an amino-PEG starter with 1.5 equivalents of protected BOC-D-Glu-OH per chain end, 1.45 equivalents of PyBOP, and 3.0 equivalents of DIPEA in NMP at 0–5°C for 4 hours per cycle. After each coupling, Boc removal is performed with TFA/TIS/H2O 95:2.5:2.5 for 20 minutes, and the product is precipitated from methyl tert-butyl ether at -20°C. Branching is controlled by monitoring the polydispersity index; if the index exceeds 1.2, the coupling sequence is paused and the protected intermediate is repurified by preparative HPLC. Residual palladium from allyl deprotection is controlled under ICH Q3D(R2), and residual NMP is reported according to ICH Q3C(R8). Published data for this specific D-configuration linker configuration is limited; process robustness therefore depends on batch-specific chromatographic analysis using charged aerosol detection because the oligo-γ-glutamate structure lacks a strong UV chromophore. Terminal output is a protected oligo-γ-glutamate linker intermediate for conjugation to cytotoxic payloads in early-stage drug development.
Competitive BOC-D-glutamic Acid prices that fit your budget—flexible terms and customized quotes for every order.
For samples, pricing, or more information, please contact us at +8615365186327 or mail to admin@ascent-chem.com.
We will respond to you as soon as possible.
Tel: +8615365186327
Email: admin@ascent-chem.com
Flexible payment, competitive price, premium service - Inquire now!
Boc-D-glutamic acid, catalogued as Boc-D-Glu-OH and systematically named (2R)-2-[(tert-butoxycarbonyl)amino]pentanedioic acid, is a protected D-amino acid building block used in peptide synthesis and chiral intermediate manufacture. The empirical formula is C10H17NO6, the molecular weight is 247.25 g/mol, and the CAS registry number is 34404-28-9. The product is supplied as a white to off-white crystalline powder. Commercial model designations vary by packaging, documentation, and quality grade; common grades include research-grade, high-purity peptide-synthesis grade, and GMP-compliant grade for pharmaceutical intermediates. The chemical identity remains constant across these model suffixes, but batch-specific certificates of analysis should be reviewed for residual solvent profile, chromatographic purity, and storage history.
Representative release specifications are listed in Table 1. The free γ-carboxyl form is defined by the absence of a benzyl, cyclohexyl, or tert-butyl side-chain protecting group at the 5-position. This structural feature changes solubility, coupling strategy, side-chain orthogonality, and final cleavage behavior relative to side-chain-protected analogs.
| Attribute | Acceptance Range or Criterion | Reference Method |
|---|---|---|
| Achiral purity by HPLC | ≥ 98.5 area-% | Ph. Eur. 2.2.29 / USP <621>; C18, 150 mm × 4.6 mm, 5 µm, detection at 210 nm |
| Enantiomeric purity | ≥ 99.0% | Chiral HPLC; enantiomeric ratio ≥ 99.0:1.0 |
| Specific rotation | +9.0° to +11.0° (c = 1, methanol, 20°C) | Ph. Eur. 2.2.7 |
| Solubility | Clear solution at 1.0 g/10 mL in DMF | Visual inspection |
| Loss on drying | ≤ 0.5% | Ph. Eur. 2.2.32 |
| Residue on ignition | ≤ 0.1% | USP <281> |
| Elemental impurities | ≤ 10 ppm total heavy metals; ICH Q3D risk assessment | ICP-MS after acid digestion |
| Residual solvents | Methanol ≤ 3000 ppm; ethyl acetate ≤ 5000 ppm | ICH Q3C, Ph. Eur. 2.4.24 |
| Storage condition | 2–8°C, desiccated, inert atmosphere | Certificate of analysis |
Two preparative routes are commonly encountered in bulk manufacture. Direct tert-butoxycarbonylation of D-glutamic acid using di-tert-butyl dicarbonate in aqueous dioxane is typical for high-purity peptide-synthesis grades; this route requires residual dioxane monitoring under ICH Q3C Class 2 limits. The alternate route using Boc protection under pH-controlled aqueous conditions may produce a different related-substance profile, particularly residual D-glutamic acid and lactam formation. The batch-specific certificate should therefore be checked when transferring between suppliers or grades.
The principal structural difference between Boc-D-Glu-OH and Boc-D-Glu(OBzl)-OH or Boc-D-Glu(OtBu)-OH is the ionizable γ-carboxyl group. In the free-acid form, the γ-carboxyl is available for post-assembly modification, resin-bound cyclization, or solution-phase amidation without a preliminary hydrogenolysis or acidolysis step. In contrast, the 5-benzyl ester is selectively removed by catalytic hydrogenation or strong acid, while the 5-tert-butyl ester is removed under acid conditions that also cleave the Boc group. The free γ-carboxyl therefore reduces the number of orthogonal deprotection steps but also introduces competition for activated amino groups during solid-phase coupling.
Compared with Boc-L-glutamic acid, the D-enantiomer differs in optical rotation sign, retention on chiral stationary phases, and biological recognition. Peptides containing D-glutamic acid are generally more resistant to degradation by endogenous L-peptidases; however, published data for a given sequence must be generated under defined assay conditions because stability depends on primary sequence and higher-order conformation. The enantiomeric pair is resolved under chiral HPLC conditions using a macrocyclic glycopeptide or ligand-exchange column; acceptance is based on an enantiomeric ratio of at least 99.0:1.0.
| Product Form | Amino Protection | γ-Carboxyl Status | Removal Conditions | Typical Use in Synthesis |
|---|---|---|---|---|
| Boc-D-Glu-OH | Acid-labile Boc | Free acid | TFA/HF | N-terminal D-Glu, γ-modification, solution-phase coupling |
| Boc-L-Glu-OH | Acid-labile Boc | Free acid | TFA/HF | L-peptide synthesis under Boc/Bzl strategy |
| Boc-D-Glu(OBzl)-OH | Acid-labile Boc | Benzyl ester | HF or hydrogenolysis | Internal D-Glu residues in Boc SPPS |
| Fmoc-D-Glu-OH | Base-labile Fmoc | Free acid | Piperidine/TFA | Fmoc solid-phase assembly |
| D-Glutamic acid | Unprotected | Free acid | Not applicable | Solution-phase synthesis requiring temporary protection |
The free-acid form is not normally selected for internal incorporation in Boc solid-phase peptide synthesis when the side-chain carboxyl must remain protected during chain assembly. In that configuration, the unprotected γ-carboxyl can compete for activated amino acid, leading to branched sequences or γ-acyl products. Side-chain-protected variants such as Boc-D-Glu(OBzl)-OH or Boc-D-Glu(OcHex)-OH are preferred for internal positions. By contrast, the free-acid form is suitable for N-terminal D-glutamic acid residues, for syntheses in which the γ-carboxyl is intentionally left free, and for routes requiring direct attachment of the side-chain carboxyl to a resin or linker.
On a bench-scale or pilot-scale solid-phase synthesizer with a reactor volume of 250 mL and a resin substitution of 0.35–0.50 mmol/g, Boc-D-Glu-OH is coupled as the free acid after preactivation. A typical coupling protocol uses 3.0 equivalents of the amino acid relative to resin-bound amine, 3.0 equivalents of HOBt, and 3.0 equivalents of DIC in DMF or dichloromethane/DMF. Activation is performed at 0–4°C for 3–5 min before addition to the resin. Coupling is continued for 30–60 min at 20–25°C. Residual free amine is checked by Kaiser test or bromophenol blue; if residual amine exceeds approximately 1.0%, a recoupling cycle with fresh activated acid is executed. The free γ-carboxyl can deprotonate under basic reaction conditions, but activation with carbodiimide/HOBt does not require strongly alkaline pH; this limits carboxylate-related side reactions.
The Boc group is removed from the growing peptide chain with trifluoroacetic acid in dichloromethane, commonly 30–50% v/v, using two treatments of 5 min each at 20–25°C. Neutralization with 5% DIEA in dichloromethane or DMF is performed before the next coupling. Final cleavage of a peptide containing free γ-carboxyl D-Glu residues from Boc/Bzl resin typically requires anhydrous hydrogen fluoride at 0°C for 1 h with 10% anisole or a scavenger mixture. The free γ-carboxyl is stable under these acidic cleavage conditions, but formate or trifluoroacetate salts may be present depending on workup.
Residual water in the coupling solvent above 100 ppm reduces active ester lifetime and can lower coupling efficiency. The building block itself should be pre-dried if loss on drying exceeds 0.5% or if ambient relative humidity has exceeded 60% during open handling. Drying in vacuo at 35°C to constant weight is used before large-scale couplings. Batch-to-batch variance in residual solvent content or particle size can alter dissolution time in DMF; milling or pre-dissolution in a smaller solvent volume is used on process lines where feed rate is sensitive to solid handling.
Independent confirmation of enantiomeric purity is performed by chiral HPLC and polarimetry because each method detects different failure modes. Chiral HPLC detects contamination by the L-enantiomer after derivatization or direct injection on a chiral stationary phase. The acceptance criterion is ≥99.0% peak area for the D-enantiomer. Polarimetry provides a batch-specific specific rotation value of +9.0° to +11.0° at 20°C with c = 1 in methanol under Ph. Eur. 2.2.7. A deviation outside this window indicates either enantiomeric contamination, residual solvent issues, or decomposition to D-glutamic acid.
For pharmaceutical intermediate qualification, related substances are monitored by HPLC with detection at 210 nm. The principal related substances are unprotected D-glutamic acid and the possible pyroglutamic acid derivative arising from intramolecular cyclization. The free γ-carboxyl form can cyclize under acid catalysis or prolonged storage above 25°C; the HPLC method is therefore designed to separate the product from these polar related substances without derivatization. Method specificity is confirmed by forced-degradation screening, but published data for this specific configuration is limited because most literature describes L-amino acid stability rather than D-enantiomer stability under identical conditions.
Residual solvent testing under ICH Q3C is required because methanol and dioxane are common process solvents. Methanol is controlled at ≤ 3000 ppm as a Class 2 solvent, and ethyl acetate is controlled at ≤ 5000 ppm as a Class 3 solvent. Elemental impurity risk assessment under ICH Q3D is expected for GMP lots used in injectable or parenteral peptide routes; the product is typically specified at ≤ 10 ppm total heavy metals by ICP-MS after digestion.
Storage of the dry solid at 2–8°C under inert gas limits thermolytic loss of the tert-butoxycarbonyl group. The Boc group can release carbon dioxide and isobutylene under acid catalysis or prolonged thermal stress; residual TFA from the synthesis route accelerates this process. The product should not be stored in contact with strong acids, strong oxidizing agents, or primary amines. Exposure to ambient moisture above 60% relative humidity for more than 4 h can cause clumping and hydrolysis to D-glutamic acid. For peptide-synthesis use, any suspected hydrolyzed material should be rejected if LOD or related-substance data fall outside the specification ranges in Table 1.
