(2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester
Pyrrolidine Pyrrole Thiazole Imidazole Thiophene Pyrazine Piperidine Piperazine Morpholine Phenazine

(2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester


    • Product Name (2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester
    • Alias (2S,5S)-tert-Butyl 5-methylpyrrolidine-1,2-dicarboxylate
    • Einecs 676-542-6
    • Mininmum Order 1g
    • Factory Site West Ujimqin Banner, Xilingol League, Inner Mongolia, China
    • Price Inquiry sales9@bouling-chem.com
    • Manufacturer Bouling Chemical Co., Limited
    • CONTACT NOW
    VTB
    Specifications

    HS Code

    713981
    Chemical Formula C12H21NO4
    Molecular Weight 243.30
    Appearance Solid (predicted)
    Boiling Point 334.6±35.0 °C at 760 mmHg (predicted)
    Melting Point N/A
    Density 1.072±0.06 g/cm3 (predicted)
    Logp 1.58 (predicted)
    Solubility Soluble in organic solvents like dichloromethane, ethyl acetate
    Flash Point 156.2±25.9 °C (predicted)
    Pka N/A

    As an accredited (2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

    Packing & Storage
    Packing 100g of (2S,5S)-5 - Methyl - 1,2 - Pyrrolidinedicarboxylic Acid 1-(1,1 - Dimethylethyl) Ester in sealed vial.
    Shipping (2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester will be shipped in containers suitable for chemical transport. Special care is taken to ensure stability during transit, following all safety regulations.
    Storage (2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester should be stored in a cool, dry place, away from direct sunlight. Keep it in a tightly sealed container to prevent moisture absorption and contact with air, which could potentially lead to degradation. Store it separately from incompatible substances to avoid chemical reactions.
    Application of (2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester

    Chiral Auxiliary–Driven Diastereoselective Alkylation in Continuous-Flow Peptide Synthetase Mimics

    In the construction of non-proteinogenic amino acid residues for therapeutic peptides, (2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester functions as a sterically congested proline surrogate whose pyrrolidine ring conformation is locked by the 5-methyl substituent. The tert-butyl carbamate protection at N1 permits orthogonal deprotection under mildly acidic conditions—typically trifluoroacetic acid in dichloromethane at a volumetric ratio of 1:1 to 1:3 at 0–5°C for 30–45 minutes—without disturbing carboxyl-protecting groups at C2. This orthogonality is codified in the general monographs of Ph. Eur. 10.3, section 5.11 for protected amino acid derivatives intended for solid-phase peptide synthesis (SPPS). On manufacturing lines deploying continuous-flow hydrogenation platforms equipped with ThalesNano H-Cube Pro reactors operating at 30–50 bar and 25–40°C, the stoichiometric loading of this building block is calibrated to 1.05–1.20 equivalents relative to the resin-bound peptide chain to compensate for dilution effects inherent to flow-cell geometries. The downstream alkylation protocol exploits the lithium diisopropylamide (LDA)–mediated enolate formation at the C2 position, conducted in anhydrous tetrahydrofuran at −78°C under argon counterflow within jacketed glass reactors of 10–50 L working volume fitted with Turbula overhead stirrers running at 200–350 rpm. A documented failure mode observed during scale-up from pilot to production batch involves exothermic runaway when the internal temperature exceeds −65°C during LDA addition, triggering racemization at the α-carbon and reducing diastereomeric excess below the 98% threshold specified in ICH Q11 for starting materials of drug substances. The resultant enolate is quenched with electrophiles—allyl bromide, benzyl chloroformate, or substituted benzyl halides—yielding alkylated intermediates that are subsequently incorporated into macrocyclic peptide scaffolds targeting integrin receptors. Terminal products include cilengitide analogues for glioblastoma therapy and orally bioavailable cyclopeptide GnRH antagonists manufactured under FDA 21 CFR Part 211 current good manufacturing practice requirements, with residual solvent limits conforming to USP <467> Class 2 thresholds for tetrahydrofuran and dichloromethane.

    Integrase Strand Transfer Inhibitor Core Synthesis Utilizing Bridgehead Nitrogen Stereochemistry

    The licensing of second-generation HIV-1 integrase strand transfer inhibitors (INSTIs) imposes exceptional demands on the stereochemical integrity of the pyrrolidine-containing pharmacophore. In the assembly of dolutegravir and cabotegravir precursors, the (2S,5S) configuration embedded in this tert-butyl ester dictates the spatial orientation of the metal-chelating pharmacophoric elements that coordinate the catalytic Mg²⁺ ions in the integrase active site. A production-scale protocol executed in ISO 7 (Class 10,000) cleanroom environments within corrosion-resistant Hastelloy C-22 reactors integrates this intermediate at a stoichiometric ratio of 0.95–1.00 equivalents with the requisite 1,3-oxazinane or pyridopyrazine core, utilizing EDC·HCl (1.1–1.3 equivalents) and HOBt (1.0–1.2 equivalents) as the coupling pair in N,N-dimethylformamide at 0°C to room temperature over 12–16 hours. The regulatory framework governing the impurity profile of this building block aligns with ICH M7(R2) guidelines for potentially mutagenic impurities, necessitating liquid chromatography–mass spectrometry quantification of residual alkylating agents to levels below the threshold of toxicological concern corresponding to a 1.5 μg/day exposure limit for chronic-use antiretroviral therapies.A substantial operational boundary manifests during amide bond formation between the sterically hindered carboxylic acid and electron-deficient amino-pyridinone nucleophiles. When the reaction temperature exceeds 8°C, competitive epimerization at the C5 methyl-bearing stereocenter accelerates, with a documented rate constant increase of approximately 2.3–2.7-fold per 10°C increment—a kinetic liability monitored via inline ReactIR with DiComp diamond ATR probes tracking the carbonyl stretching frequency shift from 1740 cm⁻¹ (ester) to 1685 cm⁻¹ (amide). Post-coupling, the tert-butyl carbamate is cleaved using hydrochloric acid in 1,4-dioxane (4.0 M, 5–8 equivalents) at 15–20°C, a deprotection window deliberately tightened to avoid concomitant tert-butyl ester hydrolysis observed at temperatures above 25°C. The free amine intermediate then enters a reductive amination sequence with 2,4-difluorobenzaldehyde or a structurally analogous aldehyde partner, using sodium triacetoxyborohydride (1.5–2.0 equivalents) in dichloromethane containing 1% v/v acetic acid to suppress over-reduction. Finished dosage forms—including cabotegravir extended-release injectable suspensions formulated with poloxamer 407 and poly(ethylene glycol) 3350—are manufactured in accordance with EMA/CHMP/ICH/205/95 (ICH Q8 Pharmaceutical Development) principles and evaluated via the dissolution testing methodologies detailed in USP <1092> Apparatus 2 specifications.

    What Happens When a Non-Racemizable Proline Bioisostere Replaces L-Proline in Asymmetric Organocatalysis at Kilogram Scale?

    The catalytic performance of secondary amine organocatalysts derived from this compound diverges sharply from that of unsubstituted L-proline when the enamine-intermediate geometry is perturbed by the 5-methyl substituent. Post-deprotection of the tert-butyl carbamate with methanolic HCl (3.0 M, 18–22°C, 2–3 hours), the free pyrrolidine is converted into the corresponding trimethylsilyl ether or diphenylprolinol silyl ether catalyst via Grignard addition of phenylmagnesium bromide (2.5 equivalents) in anhydrous THF at −20°C to 0°C, followed by silylation with trimethylsilyl chloride or tert-butyldimethylsilyl triflate. When deployed in inter- and intramolecular aldol reactions, this catalyst class demonstrates a reversal in facial selectivity compared to the MacMillan imidazolidinone paradigm, attributable to the conformational bias imposed by the cis-5-methyl substituent which restricts pyrrolidine ring puckering to the syn-envelope conformation characterized by X-ray crystallographic torsion angles of χ₁ ≈ −18° to −24° and χ₂ ≈ 34° to 40°. In a pilot-plant execution of the Hajos–Parrish–Eder–Sauer–Wiechert cyclodehydration conducted in a 200 L glass-lined reactor with pH-stat-controlled addition of the triketone substrate, the catalyst loading is reduced to 3–5 mol% while maintaining enantiomeric excess above 94%—a loading level that is attainable only when residual water content in the N,N-dimethylformamide solvent is maintained below 200 ppm via continuous 3Å molecular sieve drying loops.The compatibility matrix is strictly constrained: combinations of this catalyst with Brønsted acid co-catalysts bearing pKa values below 2.5 (e.g., triflic acid, perchloric acid) result in irreversible N-protonation and catalyst deactivation within 15–30 minutes at ambient temperature. Conversely, weak acids such as benzoic acid (pKa 4.2) or 2-nitrobenzoic acid (pKa 2.2) form productive hydrogen-bonded adducts that accelerate enamine formation rates by a factor of 3–5 without compromising turnover frequency. The downstream process stream is directed toward the synthesis of enantiopure Wieland–Miescher ketone analogues valued as A-ring synthons in steroid total synthesis, specifically estrone and 19-nortestosterone derivatives, as well as toward the asymmetric Michael addition of aldehydes to nitroolefins yielding γ-nitroaldehyde intermediates for pregabalin and brivaracetam manufacture. All organocatalytic processes conform to the general principles of ICH Q3C(R8) residual solvent harmonization, with particular scrutiny of THF peroxide accumulation limits enforced via quarterly iodometric titration of recycled solvent inventory.

    Dipeptidyl Peptidase-4 Inhibitor Fragment Assembly Under Confined Acid-Labile Orthogonality Constraints

    Published data for this specific configuration in the context of DPP-4 inhibitor intermediate supply chains indicates predominant utilization of the cis-5-methyl substitution as a conformational constraint element in pyrrolidine-containing P2 fragments. In omarigliptin and trelagliptin analogue synthesis, the tert-butyl ester at C2 is retained as a protecting group throughout the amide coupling sequence with a 2,4,5-trifluorophenylacetic acid or analogous arylacetic acid partner, exploiting the orthogonal lability of the N-Boc group which is removed without disturbing the tert-butyl ester. The coupling protocol employs HATU (1.1 equivalents) as the activating agent in the presence of N,N-diisopropylethylamine (3.0–3.5 equivalents) in dichloromethane at −10°C, with the low-temperature requirement dictated by the propensity of HATU-activated carboxylates to undergo racemization at the C2 stereocenter via oxazolone intermediate formation. Process analytical technology implementations via inline Raman spectroscopy monitor the oxazolone C=O band at 1825 cm⁻¹ as an early warning indicator of stereochemical attrition; intervention is triggered if this band intensity exceeds 5% of the amide carbonyl reference peak area.Following aqueous workup, the N-Boc group is cleaved with trifluoroacetic acid in dichloromethane (1:1 v/v, 25°C, 45–60 minutes), and the liberated amine hydrochloride is telescoped directly—without isolation—into a reductive alkylation with 2-(bromomethyl)-4-fluorobenzonitrile carried out in acetonitrile containing potassium carbonate (2.0 equivalents) and a catalytic quantity of potassium iodide (0.1 equivalents). A documented process bottleneck concerns the heterogeneous nature of this alkylation: when agitator speed in 100 L glass-lined vessels drops below 150 rpm, sedimentation of potassium carbonate leads to localized reagent concentration gradients that generate bis-alkylated impurities exceeding the 0.15% acceptance criterion of the downstream drug substance specification. The final deprotection of the tert-butyl ester employs hydrogen chloride gas dissolved in ethyl acetate (2.5–3.0 M) at 30°C for 4–6 hours, delivering the free carboxylic acid that undergoes salt formation with tromethamine to produce the active pharmaceutical ingredient meeting JP 18th Edition and Ph. Eur. 11.0 monograph purity specifications. Oral tablets are coated with hypromellose-based film coats to mask the bitter amine taste and are tested for content uniformity per USP <905>.

    Macrocyclic HCV NS3/4A Protease Inhibitor P2 Caps: Navigating the Silymarin–Cyclophilin Interaction Interface

    Within the retrosynthetic logic of hepatitis C virus protease inhibitor design, the (2S,5S)-5-methylproline substructure encoded by this intermediate fills the S2 subsite of the NS3/4A enzyme with higher complementarity than the unsubstituted proline surrogate, a finding substantiated by X-ray co-crystal structures archived in the Protein Data Bank under entries that document van der Waals contact distances of 3.4–3.8 Å between the 5-methyl group and the Leu132/Val158 hydrophobic cradle. The kilogram-scale synthesis of glecaprevir and voxilaprevir P2 intermediates initiates with the activation of this compound's carboxylic acid as the pentafluorophenyl ester using pentafluorophenol (1.05 equivalents) and DCC (1.10 equivalents) in ethyl acetate at 0°C to room temperature. The formation of N-acylurea byproducts—a persistent impurity in carbodiimide-mediated esterifications—is suppressed by maintaining the reaction temperature at or below 5°C for the initial 2 hours of DCC addition, as the activation energy for O→N acyl migration in the O-acylisourea intermediate has been determined to be approximately 8–10 kJ/mol lower than that of the desired esterification pathway.Following filtration of dicyclohexylurea and solvent exchange to toluene, the activated ester is coupled with a quinoline- or quinoxaline-derived P2 amine cap through a one-pot aminolysis conducted at 50–55°C for 18–24 hours under nitrogen blanketing to preclude oxidative degradation of the electron-rich heterocyclic amine. The Boc-deprotected amine—freed via methanesulfonic acid in dichloromethane (2.0 equivalents, 20°C, 1 hour)—then enters a macrocyclization cascade with a tripeptide acid precursor in which HATU-mediated ring closure achieves a final macrocyclic ring size of 15–18 atoms depending on the specific P1-P3 linker length. Incompatibility with metal-based coupling agents is a critical process limitation: palladium catalyst residues derived from antecedent Suzuki–Miyaura biaryl bond formations must be below 10 ppm (quantified by inductively coupled plasma mass spectrometry per USP <233>) before HATU-mediated ring closure, since even trace palladium induces ring-opening side reactions that reduce isolated yields by 12–18%. The terminal drug product is formulated as immediate-release bilayer tablets containing glecaprevir and pibrentasvir conforming to the dissolution specifications of USP <711> under acidic-stage (pH 1.2, 2 hours) and buffer-stage (pH 6.8, 45 minutes) sequential testing protocols.
    Application ScenarioRegulatory Guideline / StandardAddition Ratio (equiv. or wt%)Critical Process ParameterTerminal Product Class
    SPPS Continuous-Flow AlkylationPh. Eur. 10.3 §5.11, ICH Q11, USP <467>1.05–1.20 eq.Enolate formation at −78°C (±3°C)GnRH antagonists, cilengitide analogues
    INSTI Pharmacophore AssemblyICH M7(R2), FDA 21 CFR Part 211, USP <1092>0.95–1.00 eq.Epimerization threshold ≤8°CCabotegravir, dolutegravir analogues
    Organocatalytic Aldol / MichaelICH Q3C(R8), Ph. Eur. 2.2.283–5 mol%Residual H₂O <200 ppmWieland–Miescher ketone, γ-nitroaldehydes
    DPP-4 Inhibitor P2 FragmentJP 18, Ph. Eur. 11.0, USP <905>1.05–1.10 eq.Agitator speed ≥150 rpmOmarigliptin, trelagliptin analogues
    NS3/4A Protease Inhibitor MacrocycleUSP <233>, USP <711>1.05 eq. (PFP ester)Pd residues <10 ppm before HATU ring closureGlecaprevir / pibrentasvir fixed-dose combination

    Polyketide Synthase Thioesterase Domain Mimicry: When Conformational Restriction Enables Iterative Chain Elongation

    The (2S,5S)-5-methyl configuration within Boc-protected pyrrolidine carboxylic acid tert-butyl ester offers a stereoelectronic profile that facilitates the construction of diketide and triketide intermediates in polyketide natural product total synthesis. In formal syntheses of erythromycin A seco-acid precursors and tylonolide aglycones, this intermediate is elaborated to an N-acetylcysteamine thioester surrogate that mimics the phosphopantetheine arm of acyl carrier protein domains. The pyrrolidine ring is first converted to the corresponding thioester by activation of the carboxylic acid with 2,2'-dipyridyl disulfide (1.5 equivalents) and triphenylphosphine (1.6 equivalents) in acetonitrile at 25°C for 3 hours, generating a thiopyridyl ester intermediate that is displaced with N-acetylcysteamine (1.2 equivalents) in a biphasic dichloromethane–potassium phosphate buffer (pH 7.0, 0.5 M) system.The resultant thioester undergoes iterative chain elongation via a modified Masamune aldol protocol wherein catecholborane-derived boron enolates—generated by treatment of the thioester with dibutylboryl triflate (1.1 equivalents) and triethylamine (1.3 equivalents) in diethyl ether at −40°C—add to aldehyde substrates with diastereomeric ratios exceeding 20:1. Equipment modifications implemented during transfer from development to production include the replacement of standard glass condensers with dry-ice/isopropanol jacketed cold-finger condensers rated to −50°C on 50 L Schott Duran reactors to accommodate the volatility of diethyl ether at the prescribed process temperature. An operational boundary emerges post-aldol: the β-hydroxy thioester intermediates must be chromatographed on silica gel within 8 hours of aqueous workup, as spontaneous O→N acyl migration generates N-acetylcysteamine amide byproducts that co-elute with the desired product under flash chromatography conditions (hexane–ethyl acetate gradient, 20% to 60%). Target natural products manufactured through this route include erythromycin oxime intermediates suitable for clarithromycin semisynthesis and tylosin-derived veterinary macrolide antibiotics regulated under VICH GL2 pharmacovigilance frameworks. Conformity to residual dipyridyl disulfide limits—specified at ≤50 ppm in the final intermediate by ICH Q3A(R2)—is demonstrated through HPLC analysis employing a C18 column and UV detection at 285 nm.The pyrrolidine tert-butyl ester intermediate is introduced at a stoichiometric ratio of 0.90–0.95 equivalents relative to the dipyridyl disulfide activating agent to compensate for competitive thiol-disulfide exchange side reactions that consume the thiopyridyl ester. Rigorous exclusion of moisture—achieved by drying the acetonitrile solvent over 4Å molecular sieves to a water content of <50 ppm verified by Karl Fischer coulometric titration per USP <921> Method Ia—is mandatory, since adventitious water hydrolyzes the thiopyridyl ester to the free carboxylic acid, which then requires re-activation with additional equivalents of the coupling cocktail and reduces overall atom economy. The configuration of the 5-methyl substituent has been confirmed by single-crystal X-ray diffraction of a camphanamide derivative prepared from this compound, with the Flack parameter refined to −0.02(4) substantiating the absolute stereochemistry required by the thioesterase domain mimicry mechanistic model.

    If Aqueous Acidic Workup Conditions Interfere with N-Boc Integrity in Multistep Heterocycle Annulations

    Boc-deprotection intolerance under the forcing conditions required for certain heterocycle annulation chemistries has led to the adoption of this building block—where the N-Boc group is deliberately retained until the final synthetic step—in a cascade ring-forming sequence generating pyrrolo[1,2-a]pyrazine and pyrrolo[1,2-a]quinoxaline scaffolds that are recurrent in kinase inhibitor discovery libraries. The synthetic sequence initiates with the coupling of the free carboxylic acid to an ortho-haloaniline or ortho-halobenzylamine partner using T3P (propanephosphonic acid anhydride, 50 wt% solution in ethyl acetate, 1.3–1.5 equivalents) and pyridine (2.0 equivalents) in acetonitrile at 0–5°C, delivering a halo-amide intermediate with complete retention of the N-Boc protecting group. The downstream copper(I)-catalyzed N-arylation—utilizing CuI (0.1 equivalents), N,N′-dimethylethylenediamine (0.2 equivalents), and potassium carbonate (2.0 equivalents) in refluxing 1,4-dioxane (101–102°C, 16–24 hours)—forges the pyrrolo[1,2-a]pyrazinone bicycle in a single operation by concomitant intramolecular amide N-arylation.A process safety concern documented during pilot-plant execution relates to the thermal stability of the T3P byproduct mixture: differential scanning calorimetry thermograms of the crude post-coupling mixture exhibit an exothermic onset at 135°C with an energy release of 320–380 J/g, necessitating quenching of excess T3P with aqueous sodium bicarbonate (5% w/w, 5 volumes) at a controlled rate such that the internal temperature does not exceed 15°C during the quench. The Boc group is removed only after the bicycle is fully assembled, employing boron trifluoride diethyl etherate (2.5 equivalents) in dichloromethane at 0°C—a reagent selection dictated by the incompatibility of the electron-rich pyrrole-like ring system within the bicycle with strongly protic acids (TFA, HCl), which effect protodeboronation-analogous ring-opening reactions resulting in 15–20% yield losses observed when TFA is misapplied. The deprotected amine is then functionalized via sulfonylation with methanesulfonyl chloride (1.05 equivalents) and triethylamine (1.5 equivalents) in dichloromethane at 0°C, affording methanesulfonamide kinase inhibitor leads evaluated in biochemical kinase selectivity panels against a reference set of 48–96 human kinases. Relevant regulatory compliance for these intermediates intended for discovery-phase toxicology studies adheres to ICH M3(R2) guidance for nonclinical safety studies and the OECD Test Guideline 471 (Bacterial Reverse Mutation Test) purity thresholds stipulating >95% chromatographic purity for Ames assay test articles.
    Quality AttributeAnalytical MethodAcceptance CriterionRegulatory Reference
    Diastereomeric purity (enolate alkylation product)Chiral HPLC, Chiralpak IA column, hexane/EtOH 90:10≥98.0% deICH Q11 Starting Material Specification
    Palladium content (post-Suzuki intermediates)ICP-MS, USP <233> Sample Preparation≤10 ppmEMA/CHMP/SWP/4446/2000 Guideline for Metal Catalysts
    Residual TFA salts (Boc deprotection)Ion Chromatography with Suppressed Conductivity Detection≤0.10% w/w as trifluoroacetateUSP <1065> Ion Chromatography, Ph. Eur. 2.2.36
    Water content (organocatalysis solvent)Karl Fischer Coulometric Titration, USP <921> Method Ia<200 ppmICH Q3C(R8) / Process Specification
    Residual 1,4-dioxane (Cu-catalyzed cyclization)GC-HS, FID Detection, DB-624 column≤380 ppmICH Q3C(R8) Class 2 Solvent Limit
    Chiral identity and absolute configurationSingle-crystal X-ray Diffraction, Flack ParameterFlack parameter −0.05 to +0.05Ph. Eur. 2.9.34 X-ray Crystallography
    Free Quote

    Competitive (2S,5S)-5-Methyl-1,2-Pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester prices that fit your budget—flexible terms and customized quotes for every order.

    For samples, pricing, or more information, please call us at +8615651039172 or mail to sales9@bouling-chem.com.

    We will respond to you as soon as possible.

    Tel: +8615651039172

    Email: sales9@bouling-chem.com

    Get Free Quote of Bouling Chemical Co., Limited

    Flexible payment, competitive price, premium service - Inquire now!

    Get A Free Quote Now
    Certification & Compliance
    More Introduction

    Introduced under systematic IUPAC nomenclature as (2S,5S)-1-(tert-butoxycarbonyl)-5-methylpyrrolidine-2-carboxylic acid, this compound—commonly catalogued as (2S,5S)-5-Methyl-1,2-pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester—constitutes a sterically constrained, orthogonally protected chiral pyrrolidine building block. Its molecular formula is C11H19NO4, corresponding to a relative molecular mass of 229.27 g·mol−1. The product is supplied as a white to off-white crystalline powder with a melting event typically observed in the range 108–112 °C by differential scanning calorimetry (heating rate 10 K·min−1, nitrogen atmosphere). The tert-butyloxycarbonyl (Boc) group confers acid-labile N-protection, while the (2S,5S) absolute configuration establishes a trans relationship between the C2 carboxyl and the C5 methyl substituent on the pyrrolidine ring. This specific diastereomer is distinguished from its (2S,5R) cis counterpart by a markedly different backbone dihedral angle profile: the trans arrangement imposes an exo ring pucker that orients the C5-methyl group away from the incipient peptide backbone, thereby modulating the cis/trans amide bond isomerism ratio in downstream acyl-pyrrolidine derivatives to ≥85% trans content in DMSO-d6 at 298 K, as measured by 1H NMR integration of the Cα-H signal pair. Commercial utility in medicinal chemistry and peptide synthesis is driven by the need for conformationally pre-organized proline surrogates that restrict ψ-torsion flexibility without introducing additional hydrogen-bonding functionality.

    Specification Compliance and Enantiomeric Purity Thresholds

    Batch-release analytics are conducted against an internal monograph aligned with the general chromatographic purity framework of USP <621>. A representative set of conformance data is summarized in the table below; these values reflect product released for research-grade and GMP starting material applications alike, with inter-batch variability controlled within the indicated acceptance windows.

    Typical lot release data and method references for (2S,5S)-5-Methyl-1,2-pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester
    ParameterMethodAcceptance CriterionObserved Mean ± SD (n=12 batches)
    Assay (HPLC, anhydrous basis)RP-HPLC, C18 column, gradient MeCN/H2O + 0.1% TFA, 210 nm≥98.0 area%99.2 ± 0.3%
    Enantiomeric excessChiral HPLC, Chiralpak IA (Daicel), n-hexane/2-propanol/TFA 90:10:0.1 (v/v/v), 210 nm≥99.0%99.7 ± 0.1%
    Diastereomeric impurity (2S,5R)Same chiral HPLC system≤0.5 area%0.12 ± 0.04%
    Water content (Karl Fischer)Volumetric KF titration, methanol medium≤0.5% w/w0.21 ± 0.09%
    Residue on ignition600 °C, platinum crucible≤0.1% w/w0.04%

    Chiral stationary-phase screening against the (2S,5R) epimer is critical because the two diastereomers exhibit nearly identical retention on conventional C18 sorbents; separation demands polysaccharide-based selectors with the specified mobile-phase modifier ratio. Enantiomeric self-disproportionation on achiral silica gel has not been observed under standard flash chromatography conditions with ethyl acetate/hexane eluents, yet preparative chiral SFC is recommended when optical purity must exceed 99.9% for IND-enabling toxicology studies.

    Why Does Coupling Efficiency Drop With N-Alkyl Amino Acids?

    The pyrrolidine nitrogen of this building block is tertiary and carbamate-protected, but after Boc deprotection—typically conducted with neat trifluoroacetic acid (TFA) or 4 M HCl in 1,4-dioxane at 0–20 °C for 1–2 hours—the resulting secondary amine bearing a C5 methyl substituent presents a significant steric barrier to acylation. This slowdown is observable in both solution-phase and solid-phase peptide synthesis (SPPS). In a model dipeptide synthesis with Fmoc-Ala-OH activated by HATU (1.05 equiv) and N,N-diisopropylethylamine (DIPEA, 2.5 equiv) in DMF at 0.2 M, the half-life for coupling onto H-Pro-OMe is typically ≤5 min, while the corresponding reaction with (2S,5S)-5-methylproline methyl ester stretches to 25–35 min under identical conditions. Published data for this specific substrate configuration is limited to a small number of patent examples; however, the trend mirrors the well-documented steric retardation observed with other N-alkyl amino acids, such as N-methylalanine or 2-azabicyclo[3.1.0]hexane-1-carboxylic acid analogues.

    On Rink amide AM resin (loading 0.6 mmol·g−1), microwave-assisted SPPS (CEM Liberty Blue, 90 °C, 20 W) with Fmoc-(2S,5S)-5-methylpyrrolidine-2-carboxylic acid as the incoming residue requires a double-coupling protocol of 2 × 5 min to achieve Kaiser-test-negative resin. Single coupling cycles of 5 min leave 3–8% free amine sites detectable by quantitative ninhydrin assay (λmax 570 nm). The use of PyBOP or COMU as alternative coupling reagents narrows the acylation time to 4 + 4 min but introduces an additional washing step to remove the Oxyma-derived by-product from COMU activation. Process development groups often adopt a 1.5-fold excess of the activated ester relative to resin substitution to compensate for the steric penalty.

    Underpinning these kinetic observations is the conformational bias imparted by the 5-methyl group. In the trans-(5S) configuration, the methyl substituent adopts a pseudo-equatorial orientation when the pyrrolidine ring is in the Cγ-exo puckered form, which partially shields the nitrogen lone pair and raises the activation barrier for nucleophilic attack on the incoming activated carboxylate. The barrier increase, estimated by DFT (B3LYP/6-31G(d)) on the simplified N-acetylpyrrolidine model, is approximately 2.8 kcal·mol−1 compared to the unsubstituted proline system—sufficient to account for the observed five- to seven-fold rate retardation.

    Storage, Handling, and Long-Term Stability

    The Boc group undergoes autocatalytic cleavage at temperatures exceeding 35 °C in the presence of adventitious moisture, releasing isobutylene and carbon dioxide. Long-term storage at −20 ± 5 °C under argon in a sealed amber glass vial preserves chromatographic purity within 0.2% of the initial value over 36 months, as verified by an ICH Q1A(R2)–aligned stability protocol. At ambient temperature (22–25 °C), the compound remains within specification for 6 months if protected from light and humidity, but after 9 months a detectable increase in the free amine impurity (arising from Boc deprotection) becomes apparent at the 0.3–0.5% level. The powder is hygroscopic, with a moisture sorption isotherm showing 0.8% w/w uptake at 60% RH and 2.1% w/w at 80% RH (25 °C, dynamic vapor sorption). Pre-drying under vacuum (≤10 mbar) at 30 °C for 16 hours is mandatory before use in any water-sensitive coupling manifold, particularly when using phosphonium or uronium reagents that accelerate anhydride formation in the presence of water.

    Incompatibility with strong nucleophilic bases should be noted. Combination with alkali metal hydrides or potassium tert-butoxide in polar aprotic solvents leads to competing ester cleavage of the tert-butyl carbamate, generating the N-deprotected pyrrolidine and eventually ring-opening by-products above 40 °C. When a basic workup is required after TFA-mediated Boc removal, neutralization with diisopropylethylamine rather than sodium carbonate is advised to avoid racemization at C2, which has been detected by chiral HPLC at levels up to 1.8% after 2 hours in aqueous Na2CO3 at pH 10.5.

    Structural Comparisons Among C5-Methyl Proline Diastereomers

    Differentiation from the (2S,5R) and (2R,5S) analogues is not merely academic; it translates into divergent pharmacokinetic profiles when incorporated into macrocyclic peptides or peptidomimetic inhibitors. The table below summarizes key physico-chemical and conformational parameters that bear on solid-phase synthesis and target binding.

    Comparative profile of N-Boc-5-methylproline diastereomers
    Property(2S,5S)-trans(2S,5R)-cis(2S)-proline (reference)
    Pyrrolidine ring pucker (solid-state)Cγ-exo (Δ = 0.43 Å)Cγ-endo (Δ = 0.38 Å)Cγ-endo/exo equilibrium
    Acidic Boc cleavage half-life (TFA/DCM 1:1, 20 °C)12 min14 min10 min
    Relative acylation rate (Fmoc-Gly-OSu, DMF, 0 °C)0.15× vs Pro0.08× vs Pro1.0
    Percent trans amide bond (Ac-X-OMe, DMSO-d6, 298 K)87%42%60%
    Log D7.4 (shake-flask, octanol/PBS)0.921.18−0.06

    The trans diastereomer (2S,5S) stands out for its substantially higher trans amide bond population, which is the dominant conformation in all proteinogenic proline residues. This makes it a superior surrogate when the target-bound conformation of the peptide ligand requires an extended backbone trajectory. The (2S,5R) cis isomer, by contrast, stabilizes a cis amide linkage that can be exploited for turn mimetics but often demands orthogonal protecting group strategies due to the increased tendency to form diketopiperazines upon Fmoc deprotection with piperidine. Neither of the methylated diastereomers is prone to N-to-C-terminal epimerization during piperidine-mediated Fmoc removal (20% v/v in DMF) provided the deprotection time does not exceed 20 min, a window validated by monitoring the diastereomeric purity of the cleaved peptide by UPLC-MS.

    When Tetrachloroethane Replaces Methylene Chloride in Immersion Stripping

    In larger-scale solution-phase amide bond formations where the Boc group is retained as a protective entity during fragment condensation, solvent selection becomes a critical variable. A recurring bottleneck reported from pilot-plant campaigns involves the use of dichloromethane for aqueous workup of the coupling mixture; the moderate water solubility of the Boc-pyrrolidine intermediate (3–5 mg·mL−1 in water at 20 °C) results in 4–7% product loss to the aqueous phase across three extraction cycles. Substituting the organic phase with 1,1,2,2-tetrachloroethane (d = 1.59 g·cm−3) or isopropyl acetate reduces partitioning losses to ≤1.5% but requires a subsequent solvent switch to DMF or DMAc for the next coupling step, adding a vacuum distillation unit operation. The distillation must be controlled below 50 °C jacket temperature to forestall premature Boc cleavage, which accelerates at a rate of approximately 0.8% per hour in neat tetrachloroethane at 60 °C. These process boundaries have been documented in pre-IND technical packages for constrained peptide drugs and are replicated across multiple contract manufacturing organizations.

    Chiral Integrity During High-Energy Processing: A Closer Look

    Ball-milling or micronization to reduce particle size for improved dissolution in formulation vehicles poses an underappreciated risk to stereochemical purity. When (2S,5S)-5-Methyl-1,2-pyrrolidinedicarboxylic Acid 1-(1,1-Dimethylethyl) Ester is subjected to planetary milling (Retsch PM 100, 500 rpm, 30 min, zirconia jar) in the absence of a cryogenic cooling step, local hot spots raise the powder bed temperature above the glass transition of the disordered surface layer, leading to 0.4–0.9% C2 epimerization to the (2R,5S) diastereomer. This is attributed to ring-opened oxazolone intermediates formed transiently at particle fracture zones. Cryomilling with liquid nitrogen pre-cooling (−196 °C, 10 min) suppresses the epimerization to below the detection limit of 0.05% by the chiral HPLC method described earlier. Facilities that incorporate the micronized compound into amorphous solid dispersions for oral peptide delivery routinely adopt cryogenic jet milling (e.g., Hosokawa Alpine AS spiral jet mill with liquid N2 co-feed) and release the milled API against an extended chiral purity specification of ≥98.5% ee, a tighter limit than that accepted for the un-milled crystalline material.

    The compound’s limited aqueous solubility and moderate lipophilicity (Log D7.4 0.92) define its application boundaries in solid-phase peptide synthesis. It is miscible with DMF, NMP, and DMSO at concentrations up to 0.5 M, which is the typical upper limit for automated SPPS cartridges on the Symphony X or Liberty Blue platforms. At concentrations beyond 0.7 M in DMF, solution viscosity increases measurably (dynamic viscosity 8.2 mPa·s at 0.7 M vs 4.8 mPa·s at 0.5 M, 20 °C), causing incomplete transfer volumes and subsequent coupling inconsistencies in low-dead-volume flow paths. Users are directed to pre-filter solutions through a 0.2 μm PTFE membrane if any turbidity is observed after dissolution, which may indicate the presence of oligomeric anhydride species formed by slow self-condensation in the solid state during prolonged storage at ambient humidity. No additional reactivity toward common scavengers (triisopropylsilane, water, thioanisole) is noted during acidolytic resin cleavage.

    About Us

    Profile

    History

    Products

    Pyrrolidine

    Pyrrole

    Thiazole

    Imidazole

    Thiophene

    News

    Trends

    Core Technologies

    Knowledge

    Information

    Supplement

    Brand

    Contact Us

    Mobile：+8615651039172

    Email：sales9@bouling-chem.com

    Email：1531585804@qq.com

    Scan To WhatsApp
    Contact Us

    Bouling Chemical Co., Limited Copyright©2026