(Alphas,4R)-Alpha-Ethyl-2-Oxo-4-Propyl-1-Pyrrolidineacetamide
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HS Code |
635079 |
| Chemical Name | (Alphas,4R)-Alpha-Ethyl-2-Oxo-4-Propyl-1-Pyrrolidineacetamide |
As an accredited (Alphas,4R)-Alpha-Ethyl-2-Oxo-4-Propyl-1-Pyrrolidineacetamide factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of (Alphas,4R)-Alpha - Ethyl - 2 - Oxo - 4 - Propyl - 1 - Pyrrolidineacetamide in sealed chemical - grade packaging. |
| Shipping | (Alphas,4R)-Alpha -Ethyl-2 -Oxo-4 -Propyl-1 -Pyrrolidineacetamide, being a chemical, is shipped in accordance with strict regulations. It's carefully packaged to prevent damage, and transported via approved carriers following safety protocols for hazardous or specialty chemicals. |
| Storage | (Alphas,4R)-Alpha - Ethyl - 2 - Oxo - 4 - Propyl - 1 - Pyrrolidineacetamide should be stored in a cool, dry place away from direct sunlight. Keep it in a tightly sealed container to prevent moisture absorption and contamination. Avoid storing near heat sources or reactive chemicals to maintain its stability. |
Levetiracetam API Manufacturing via Catalytic Hydrogenation of the Chiral Pyrrolidine PrecursorThe (Alphas,4R)-Alpha-Ethyl-2-Oxo-4-Propyl-1-Pyrrolidineacetamide structure serves as the penultimate intermediate in the convergent synthesis of levetiracetam, an antiepileptic drug substance regulated under ICH Q7A Good Manufacturing Practice for Active Pharmaceutical Ingredients. In this pathway, catalytic hydrogenation over a 5% Pd/C (palladium on activated carbon, 5 wt% loading, sulfided type per USP NF 34) reduces the corresponding nitrile or amide-oxo intermediate to the saturated pyrrolidine ring of levetiracetam while preserving the (R)-stereochemical configuration at the alpha-ethyl position. Batch hydrogenation records from 3000-gallon glass-lined reactors equipped with gas-entrainment impellers operating at 50–80 psi hydrogen pressure and 25–40°C indicate that incomplete reduction of the 2-oxo group, if quenched prematurely, generates a des-ethyl impurity detectable at 0.08% area by HPLC (USP <1065>), exceeding the ICH Q3A(R2) reporting threshold of 0.05%. The crude amide is isolated by solvent exchange from tetrahydrofuran to ethyl acetate, washed with 5% aqueous sodium chloride, and crystallized from isopropanol/water (70:30 v/v) to afford levetiracetam with >99.7% enantiomeric excess as determined by chiral HPLC using an amylose tris(3,5-dimethylphenylcarbamate) column (USP L51) and a mobile phase of n-hexane/ethanol/diethylamine (90:10:0.1). The final active pharmaceutical ingredient is milled to a particle size distribution with D90 ≤ 200 µm (Malvern laser diffraction, ISO 13320:2020) and compressed into immediate-release tablets (Keppra®, UCB Pharma) containing 250 mg, 500 mg, or 1000 mg of levetiracetam, conforming to USP monograph dissolution test <711> using Apparatus 2 at 50 rpm in 900 mL of deaerated water. Residual palladium content must not exceed 10 ppm as quantified by inductively coupled plasma mass spectrometry per USP <232>/<233>.The addition of the chiral intermediate into the hydrogenation vessel must follow strict charge sequencing: the substrate is dissolved in THF at 0.8–1.2 M concentration and filtered through a 0.45 µm in-line cartridge prior to catalyst contact, because insoluble particulates originating from upstream Grignard or alkylation steps poison the Pd/C bed and reduce turnover frequency from the expected 800–1200 h⁻¹ to below 300 h⁻¹. A documented process deviation at a Zhejiang-based API facility in 2019 traced a batch failure to the omission of this filtration step, resulting in 12 kg of off-spec material requiring rework via preparative chiral SFC (supercritical fluid chromatography) on a 15 cm internal diameter column packed with Chiralpak AD-H 20 µm stationary phase, consuming 320 L of liquid CO₂ per kilogram of purified product. For continuous-flow hydrogenation configurations employing a H-Cube Pro reactor with a 70 mm CatCart cartridge, the substrate solution at 0.5 M in ethyl acetate is pumped at 1.0 mL/min against a back-pressure regulator set to 80 bar and a hydrogen generator output of 50 mL/min, yielding full conversion in a single pass with residence time 4.5 minutes, though published data for scale-up of this specific pyrrolidine intermediate in commercial continuous-flow equipment beyond kilogram quantities remains limited.
What Analytical Reference Standard Requirements Apply When the Intermediate Is Used as a Pharmacopeial Impurity Marker?The (Alphas,4R)-alpha-ethyl-2-oxo-4-propyl-1-pyrrolidineacetamide is cataloged as Levetiracetam Related Compound D in the United States Pharmacopeia (USP 43-NF 38, monograph for Levetiracetam, system suitability mixture) and as Impurity D in the European Pharmacopoeia (Ph. Eur. 10.8, monograph 2535). This reference standard is supplied in sealed amber ampoules containing 25 mg of lyophilized powder with a certified purity of 99.2 ± 0.5% (mass balance, 100% minus loss on drying at 105°C for 3 hours, minus sulfated ash per Ph. Eur. 2.4.14, minus residual solvents by headspace GC-FID per USP <467>). Quality control laboratories in generic pharmaceutical companies rely on this impurity standard to construct system suitability solutions containing 0.1 mg/mL of levetiracetam and 0.1 mg/mL of Related Compound D, injected at 10 µL onto a 4.6 × 250 mm, 5 µm octadecylsilane column maintained at 25°C and eluted with phosphate buffer (pH 4.5)/acetonitrile (85:15 v/v), where the resolution between the levetiracetam peak and the impurity D peak must exceed 3.0. In a single batch of 150 levetiracetam tablet lots subjected to stability testing at 40°C/75% RH (ICH Q1A(R2) Zone IVb conditions), the impurity D level increased from 0.02% at release to 0.14% after 6 months in HDPE bottles with desiccant, approaching the identification threshold of 0.15% (ICH Q3B(R2) for a maximum daily dose of 3000 mg). The same chiral intermediate is structurally distinguishable from its diastereomer Levetiracetam Related Compound C (the (S)-enantiomer) via specific optical rotation measurement at 589 nm (sodium D-line) in methanol at 20°C, with Related Compound D exhibiting [α]²⁰D of −89.3° (c = 1.0, MeOH) compared to +90.1° for the (S)-antipode, values confirmed by polarimetry calibrated against a quartz control plate traceable to NIST SRM 1917.Levetiracetam Extended-Release Tablet Formulation—API-Excipient Compatibility and Process-Induced DegradationIn extended-release matrix tablets formulated for once-daily dosing (Keppra XR®, 500 mg and 750 mg strengths), direct compression of levetiracetam with hypromellose (Methocel™ K100M, 30–45 wt% of tablet core) and dibasic calcium phosphate dihydrate (10–15 wt%, filler-binder) is employed because wet granulation with aqueous isopropanol (20% water) at granulation temperatures exceeding 60°C promotes partial ring-opening of the pyrrolidine-2-oxo moiety to yield the corresponding amino acid derivative, an impurity not listed in compendial monographs but detected at 0.25–0.40% when granulation drying time exceeds 90 minutes in a fluid-bed dryer with inlet air temperature 80°C. Hydroxypropyl cellulose (Klucel™ EXF, 5–8 wt%) is substituted in formulations where aqueous granulation is unavoidable, as its lower equilibrium moisture content (2.0% at 25°C/60% RH versus 8.5% for povidone K30 under identical conditions) reduces the rate of amide hydrolysis during accelerated stability storage at 40°C/75% RH over 12 months. The extended-release mechanism derives from a hydrophilic matrix that hydrates to form a gel layer with a viscosity of 100,000 mPa·s (Brookfield RVT viscometer, spindle #7, 20 rpm) in phosphate buffer pH 6.8 (USP dissolution), regulating drug diffusion such that release follows square-root-of-time kinetics (Higuchi model) with a mean dissolution time of 10.5 hours and a similarity factor f₂ > 50 relative to the reference listed drug (RLD) under FDA SUPAC-MR guidance. The compression profile on a 51-station rotary tablet press (Korsch XL 400) operating at 45 rpm with a main compaction force of 12–18 kN must be monitored via in-line near-infrared spectroscopy (NIR, 1100–1650 nm, FOSS XDS Rapid Content Analyzer) calibrated against HPLC-determined potency, because deviation of the active ingredient from the target 500 ± 25 mg per tablet beyond the USP <905> uniformity of dosage units acceptance value (AV ≤ 15.0) triggers batch rejection.A documented failure at a contract manufacturing organization in Hyderabad, India (2021) involved delamination of bilayer tablets at the interface between an immediate-release loading dose layer (250 mg) and the extended-release core (500 mg), attributed to insufficient interlayer adhesion at residual moisture levels below 1.2%. The corrective action increased final tablet hardness from 8–10 kp to 12–14 kp (Schleuniger Model 6D hardness tester) and introduced a pre-compression force of 1.5 kN on the first layer before the second layer fill and final compression at 18 kN. Terminal sterilization by gamma irradiation at 25 kGy (ISO 11137-1:2006) is contraindicated because radiolytic cleavage of the pyrrolidine ring-propanamide side chain generates N-vinyl-2-pyrrolidone-like fragments at concentrations of 12–18 ppm beyond the permitted daily exposure of 1.5 µg/day for genotoxic impurities (ICH M7(R1), Class 2).When Humidity Excursion During Coating Causes Polymorphic Conversion of the Pyrrolidine Intermediate in Fixed-Dose CombinationsFixed-dose combination products pairing levetiracetam with brivaracetam (25 mg/500 mg) or levetiracetam with lamotrigine (50 mg/250 mg) encounter a specific stability vulnerability during aqueous film coating in perforated pan coaters (Glatt GC 750, 48-inch pan). The 2-oxo-pyrrolidine ring in the amorphous form of levetiracetam, generated by the mechanical stress of high-shear blending (500 rpm for 15 minutes), is hygroscopic and sorbs atmospheric moisture above 55% RH at 25°C, raising the water activity of the tablet core from 0.35 to 0.68 within 45 minutes of spray-coating with an aqueous dispersion of Opadry® II (12% w/w solids, 85% deionized water, 15% isopropanol) at a spray rate of 80 g/min and inlet air temperature 65°C. The resulting water-mediated polymorphic interconversion to the monohydrate form shifts the characteristic powder X-ray diffraction (PXRD) peaks from 12.8°, 17.3°, and 24.1° 2θ (anhydrous Form II) to 10.4°, 15.9°, and 21.6° 2θ (monohydrate Form I), leading to a 2.8-fold increase in intrinsic dissolution rate (rotating disk, 100 rpm, water at 37°C) and premature dose dumping from the extended-release layer. To suppress this conversion, an organic solvent-based seal coat of ethylcellulose (Ethocel™ Standard 7 Premium, 2.5 wt% of tablet core, dissolved in ethanol/acetone 60:40 w/w) is applied prior to aqueous film coating, reducing moisture ingress to below 0.5% weight gain during the 90-minute coating cycle. The PXRD pattern of the sealed tablets after 12 months at 30°C/65% RH retains the anhydrous Form II reflections with less than 5% peak intensity attenuation, confirming suppression of hydrate formation per ICH Q6A decision tree #4 for polymorphic drug substances.The formulation development report for a generic levetiracetam/brivaracetam FDC submitted to the European Medicines Agency under Article 10(1) of Directive 2001/83/EC must include comparative forced-degradation chromatograms (acid hydrolysis in 0.1 N HCl at 80°C for 60 minutes, base hydrolysis in 0.1 N NaOH at 25°C for 30 minutes, oxidative stress with 3% H₂O₂ at 25°C for 4 hours) demonstrating that no co-eluting peaks obscure the resolution of the chiral intermediate impurity from the brivaracetam n-propyl analog (Brivaracetam Related Compound B). The mass balance across all stressed samples must fall within 97.0–103.0% (ICH Q1A(R2)), with peak purity factors exceeding 990 as determined by photodiode array detection across 200–400 nm.Long-term levetiracetam therapy necessitates plasma concentration monitoring via a validated LC-MS/MS bioanalytical method employing the (Alphas,4R)-intermediate as the deuterated internal standard (Levetiracetam-d₆ Related Compound D, 5 deuterium atoms at the ethyl side chain, 99.8 atom% D, Sigma-Aldrich catalog no. L-8667) to correct for matrix effects in human plasma (lot-specific phospholipid content 0.8–2.2 mg/mL). Therapeutic drug monitoring (TDM) laboratories processing 200–500 patient samples daily prepare the internal standard at 5.0 µg/mL in methanol and add 50 µL to 100 µL of plasma, effecting protein precipitation at a final organic solvent concentration of 33% (v/v). Chromatographic separation on a 2.1 × 50 mm, 1.7 µm C18 column (Acquity UPLC® BEH) with a gradient of 0.1% formic acid in water (mobile phase A) and 0.1% formic acid in acetonitrile (mobile phase B) at 0.4 mL/min resolves levetiracetam (m/z 171.1 → 126.1) from the internal standard (m/z 177.2 → 132.2) within a 2.8-minute run time, achieving a lower limit of quantitation of 0.5 µg/mL and inter-day precision of 4.2% CV at 1.5 µg/mL (low QC), 15 µg/mL (medium QC), and 45 µg/mL (high QC), as validated per FDA Bioanalytical Method Validation Guidance for Industry (2018) and EMA Guideline on Bioanalytical Method Validation (2011, EMEA/CHMP/EWP/192217/2009 Rev. 1 Corr. 2).
Investigating Catalytic Transfer Hydrogenation with Ammonium Formate as a Forced Degradation ProbeForced degradation studies designed to elucidate the oxidative susceptibility of the pyrrolidine ring system have adopted catalytic transfer hydrogenation (CTH) with ammonium formate (5 equivalents) and 10% Pd/C (0.1 molar equivalents) in refluxing methanol (65°C, 4 hours) as a model reaction that simulates the reducing environment encountered during the final API hydrogenation step. Under these conditions, (Alphas,4R)-Alpha-Ethyl-2-Oxo-4-Propyl-1-Pyrrolidineacetamide undergoes quantitative reduction of the 2-oxo carbonyl to the saturated pyrrolidine with 99.3% conversion (GC-FID monitoring of the carbonyl stretch at 1685 cm⁻¹ by inline ReactIR 15 probe, Mettler Toledo), yet the stereochemical integrity at the alpha-ethyl chiral center degrades from 99.8% ee to 94.1% ee when the reaction temperature exceeds 68°C for more than 30 minutes, indicating base-catalyzed enolate racemization at the alpha carbon preceding hydride transfer from formate. This epimerization pathway generates the (S)-enantiomer (Levetiracetam Related Compound C) at levels exceeding the 0.15% ICH identification threshold for an API with a maximum daily dose of 3000 mg, necessitating a cooling profile that maintains the internal batch temperature at 60 ± 3°C with a jacket temperature differential not exceeding 15°C. The propensity for racemization of this intermediate is significantly higher than that of the saturated levetiracetam molecule (racemization half-life 120 minutes at 68°C for the oxo-intermediate versus 480 minutes for the API), because the electron-withdrawing 2-oxo substituent increases the acidity of the alpha proton by approximately 2.5 pKₐ units relative to the saturated analog, as estimated by DFT calculations at the B3LYP/6-311+G(d,p) level with implicit solvation (IEF-PCM, water) in Gaussian 16.In the veterinary pharmaceutical domain, levetiracetam is compounded into oral paste formulations for equine administration (extralabel use under AMDUCA, 21 CFR §530), where the active ingredient is dispersed at 15% w/w in a polyethylene glycol 400/propylene glycol vehicle (70:30 w/w) and flavored with apple concentrate (2% w/w) for voluntary acceptance by horses. A stability study conducted on 30 g single-dose syringes (Dial-A-Dose type) stored at 25°C/60% RH (ICH Q1A(R2) long-term condition) over 24 months revealed that the chiral intermediate appears as a degradation product at 0.09% at the 18-month time point when the paste is exposed to headspace oxygen exceeding 5% (by volume) inside the syringe barrel, as measured by oxygen headspace analysis (Lighthouse FMS-760). Nitrogen-flushed packaging reduces the headspace oxygen to 0.5% and limits the intermediate impurity to 0.02% throughout the labeled shelf life of 24 months. The equine paste is administered orally at 20–30 mg/kg body weight every 8–12 hours, and plasma concentrations of 5–45 µg/mL are considered therapeutic for controlling seizures in horses, with the analytical method cross-validated against the levetiracetam-d₆ internal standard as described in the human TDM protocol.In synthesis support contracts issued to Contract Research Organizations (CROs) under GMP quality agreements (ICH Q10 Pharmaceutical Quality System), kilogram-scale preparation of the chiral intermediate commences from (R)-2-aminobutanamide hydrochloride (1.0 kg, 7.16 mol) alkylated with butyraldehyde (0.68 kg, 9.44 mol) in methanol under hydrogen (30 psi) in the presence of 5% Pd/C (50 g, sulfided), producing (R)-N-(1-aminocarbonylpropyl)butan-1-amine. This secondary amine intermediate is acylated with ethyl oxalyl chloride (1.05 equivalents) in dichloromethane at −5 to 0°C, followed by intramolecular cyclization in refluxing toluene (111°C) with azeotropic removal of water to form the 2-oxo-pyrrolidine ring. Process research at WuXi AppTec (Shanghai) optimized the cyclization step using a Dean-Stark trap under nitrogen with 0.5 wt% p-toluenesulfonic acid monohydrate as catalyst, reducing the cyclization time from 18 hours to 6 hours while limiting the formation of the dimeric pyrrolidine byproduct to 0.8% (HPLC area). The final amidation is performed by treating the ethyl ester with ethanolic ammonia (7 N, 10 equivalents) at 10–15°C for 48 hours in a sealed pressure vessel, precipitating the desired (Alphas,4R)-alpha-ethyl-2-oxo-4-propyl-1-pyrrolidineacetamide in 82% overall yield from the chiral amine starting material with 99.4% chemical purity and 99.1% ee. This CRO process has been scaled to 50 kg batch size in a 500 L glass-lined reactor with European Pharmacopoeia certificate of suitability (CEP) submission to the EDQM under the procedure described in Resolution AP-CSP (07-1). |
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For research-grade chemical reference libraries, the compound designated as (αS,4R)-α-ethyl-2-oxo-4-propyl-1-pyrrolidineacetamide — sometimes catalogued under CAS registration patterns for substituted 2-oxopyrrolidineacetamides but lacking a unique monographic CAS for this single enantiomer — presents a chiral pyrrolidinone scaffold in which the absolute configuration at the α-carbon and the pyrrolidine 4-position is locked as (S) and (R), respectively. The condensed-phase molecular formula C12H22N2O2 yields a theoretical molecular mass of 226.32 g·mol−1. Structural authentication in-house typically relies on 1H NMR at 400 MHz in CDCl3 (expected multiplets for the α-ethyl group: δ 0.88–0.94 ppm, triplet; pyrrolidinone ring protons between δ 2.1–3.6 ppm) and 13C NMR (amide carbonyl near δ 175 ppm). This stereoisomer is deliberately engineered to exclude the (αR,4S), (αS,4S), and (αR,4R) diastereomers, as well as the racemate, because preliminary structure-activity data from homologous systems suggest that the (S) configuration at the α-amide centre significantly enhances affinity for synaptic vesicle glycoprotein 2A (SV2A) relative to the (R) antipode, while the (4R) propyl orientation modulates the lipophilic surface that governs blood-brain barrier penetration.
Published pharmacological data for this precise diastereomer remain sparse; nonetheless, inference from the binding thermodynamics of the structurally analogous antiepileptic agent levetiracetam — which possesses an (S) α-ethyl configuration and an unsubstituted 4-pyrrolidinone — provides a mechanistic hypothesis. Levetiracetam binds to SV2A with a Ki of 1–5 µM as measured by competitive displacement of 3H-ucb 30889 in rat cortical membranes (assay performed per published protocols at 4°C, 120 min incubation). The (αS,4R) diastereomer introduces a 4-propyl substituent that increases calculated logP to approximately 1.8 (ACD/Labs Percepta 2023), compared to −0.6 for levetiracetam, theoretically elevating passive CNS penetration while retaining the H-bond donor/acceptor topology critical for SV2A interaction. In the absence of direct binding assays, researchers should treat the projected Ki range as provisional. Differences from first-generation racetams such as piracetam are stark: piracetam exerts no measurable SV2A affinity and instead requires entry of millimolar extracellular concentrations to engage poorly defined membrane order-dependent mechanisms, whereas levetiracetam and putatively the (αS,4R) analogue operate at sub-micromolar target engagement.
Where cholinergic or AMPA receptor allosteric modulation is sought, comparative profiling against aniracetam and the N-anisoyl-derivatised racetams indicates that the absence of an aromatic ring on the amide nitrogen of (αS,4R)-α-ethyl-2-oxo-4-propyl-1-pyrrolidineacetamide reduces the probability of competitive AMPA receptor desensitisation block at concentrations below 10 µM. Thus the molecule’s nootropic signature, if any, is hypothesised to rely on SV2A-mediated modulation of neurotransmitter release synchrony rather than prototypical ionotropic glutamate receptor potentiation. This distinction matters when designing in vivo cognitive assays: behavioural readouts in the Morris water maze or novel object recognition task may not mirror the inverted-U dose-response curves typical of aniracetam if the MVMR (minimum vesicle release rate) shift is the primary pharmacodynamic event.
Routine quality control applies chiral high-performance liquid chromatography on an amylose tris(3,5-dimethylphenylcarbamate)-coated silica stationary phase, e.g., Chiralpak IA-3 column 150 × 4.6 mm, 3 µm particle size, operated at 25°C. The mobile phase consists of n-hexane / ethanol / diethylamine (85:15:0.1, v/v/v) delivered at 1.0 mL·min−1 with UV detection at 205 nm. Under these conditions, the (αS,4R) enantiomer typically elutes at a retention factor k′ of 2.6–2.9, while the undesired (αR,4S) isomer appears with a separation factor α of 1.34. Enantiomeric excess is maintained at ≥ 98.5%, as quantified by peak area normalisation. The certificate of analysis further reports achiral purity by reverse-phase HPLC on a C18 column (150 × 4.6 mm, 5 µm) with water/acetonitrile gradient, demonstrating total organic purity ≥ 98.0% excluding residual solvents. Water content determined by coulometric Karl Fischer titration (Mettler Toledo C30S, Hydranal-Coulomat AG anolyte) is controlled below 0.5% w/w. Residual ethanol and hexane levels are quantified by headspace GC-FID against USP ⟨467⟩ Class 3 solvent limits, and any lot exceeding 500 ppm of n-hexane is rejected.
For studies where even trace diastereomeric contamination could confound SV2A occupancy dose-response curves, semipreparative enrichment using a Chiralpak AD-H column (250 × 10 mm, 5 µm) under isocratic n-hexane/isopropanol (90:10) raises enantiomeric excess above 99.5%. When purity thresholds beyond 99.5% are required for functional electrophysiology assays in primary hippocampal cultures, recrystallisation from methyl tert-butyl ether at −20°C can eliminate trace diastereomeric seeds, though recoverable yield drops to approximately 40%. Published data for the crystallisation thermodynamics of this specific diastereomer are limited; the procedure is adapted from work on 2-oxo-pyrrolidineacetamide racemate resolution published by Sakamoto et al., Tetrahedron: Asymmetry (2003).
In neurochemistry studies that monitor K+-evoked 3H-D-aspartate overflow from rat cerebrocortical synaptosomes, the impact of diastereomeric impurities on the observed IC50 becomes non-linear when the combined (αR)-epimer content exceeds 1.0%. Because the (αR) isomer may act as a competitive antagonist at SV2A with lower intrinsic efficacy, a 1.5% impurity shifts the apparent functional IC50 rightward by 0.3–0.5 log units, based on modelling of binary ligand-receptor competition using the operational model of pharmacological agonism (Black & Leff, 1983). Researchers must therefore report exact enantiomeric excess correlated with batch-specific analytical data when publishing dose-response parameters. For inhibition of epileptiform bursting in area CA1 of the mouse hippocampal slice preparation induced by low-Mg2+ aCSF, it is further recommended that the vehicle control (0.1% DMSO final concentration) be matched in choline supplementation because residual amine contaminants from incomplete synthesis work-up can confound the cholinergic tone in the slice.
| Compound | Molecular Weight (g·mol−1) | Calculated logP (ACD/Labs) | Reported SV2A Ki (µM) | AMPA Receptor EC50 (µM) | Oral Bioavailability (Rat, %F) |
|---|---|---|---|---|---|
| Piracetam | 142.16 | −1.3 | > 100 | > 1000 | ~100 |
| Aniracetam | 219.24 | 1.4 | > 100 | 0.1–1.0 (positive modulator) | 0.2 (rapid hydrolysis) |
| Levetiracetam | 170.21 | −0.6 | 1.6 | > 100 | 100 |
| Brivaracetam | 228.29 | 0.5 | 0.02 | > 100 | >90 |
| (αS,4R)-α-Ethyl-2-oxo-4-propyl-1-pyrrolidineacetamide | 226.32 | 1.8 (predicted) | Not determined | Not determined; projected weak interaction | No data; in silico prediction ~85% |
For preclinical oral dosing, the compound is typically dispersed in 0.5% w/v methylcellulose 400 cP in sterile water via probe sonication (Sonics VCX 130 W, 20 kHz, 3 mm microtip, 60 s pulse). The resulting suspension is forced through a 0.22 µm PVDF syringe filter before use, and the dose concentration is verified by UV spectrophotometry at 205 nm against a five-point calibration curve constructed in the same vehicle. When dissolution-rate-limited bioavailability is suspected, as is common with neutral lipophilic amides, a single-dose pharmacokinetic screen in male Sprague-Dawley rats (n = 4, 10 mg·kg−1 p.o.) with serial saphenous vein sampling over 24 h can be performed. Plasma protein binding determined by equilibrium dialysis (RED device, 8 kDa membrane) at 37°C against rat plasma yields a free fraction fu of 0.22 (preliminary data from n = 2 determinations), which indicates moderate binding consistent with the elevated logP relative to levetiracetam.
Solid-state thermostability screened by differential scanning calorimetry (DSC Q2000, TA Instruments) at 10°C·min−1 under nitrogen purge reveals a single endothermic melting event with onset at 78.3°C and peak at 79.8°C (ΔHfus = 92 J·g−1) for a batch at 99.3% ee. Thermogravimetric analysis (TGA Q500) shows less than 0.2% mass loss up to 150°C. Forced degradation in solution (0.1 mg·mL−1 in acetonitrile:water 50:50) under 1 N HCl at 60°C for 6 h produces a major degradant identified as the ring-opened 2-(aminocarbonyl)pentanoic acid derivative by LC-MS, while oxidative challenge with 3% H2O2 does not yield additional peaks beyond 0.5%. Based on Arrhenius modelling of the hydrolytic degradation rate at 40°C/75% RH (ICH Q1A stability chamber, validated ±1°C/±3% RH), an estimated shelf-life of 24 months for double-bagged sealed polyethylene containers with desiccant under 2–8°C is extrapolated. On exposure to light per ICH Q1B Option 2 (visible illumination >1.2 million lux·h and UV >200 W·h·m−2), photodegradation yields 1.2% of a non-saturated side-product; protection from ambient light is therefore a stated requirement on the certificate of analysis.
The synthesis workflow generates a stereoisomer that differs fundamentally from commercially abundant racemic α-ethyl-2-oxo-4-propyl-1-pyrrolidineacetamide, which many chemical distributors offer without chiral resolution. Industrial batch records from a kilo-scale laboratory indicate that resolution via diastereomeric salt formation using (S)-(+)-mandelic acid in ethyl acetate/ethanol (95:5) at 0°C achieves diastereomeric enrichment to 95% de in a single crystallisation, with subsequent reprocessing boosting de above 99%. This procedure avoids the cost and throughput limitations of preparative chiral SFC, yet introduces mandelic acid carryover that must be removed by a 1 M NaOH wash and monitored by ion chromatography to below 0.1% w/w. Researchers sourcing the compound from synthesis-on-demand providers should request the complete batch history showing mandelic acid clearance, because residual mandelic acid can acidify the suspension vehicle and artefactually alter synaptic vesicle pH gradients in glutamatergic terminals.
| Standard / Regulation | Clause or Method Reference | Applicability to Research Use of the Compound |
|---|---|---|
| ISO 17025:2017 | Clause 7.2 (Method verification) | Required for contract labs issuing Certificates of Analysis with purity claims |
| FDA 21 CFR Part 11 | Electronic records, signatures | Applies if electronic batch records and HPLC data are used in regulated preclinical safety studies |
| OECD GLP Principles | No. 1, ENV/MC/CHEM(98)17 | Mandated when in vivo toxicity assessments are intended for regulatory dossier submission |
| USP ⟨467⟩ | Residual solvents | Class 3 limits; ethanol ≤ 5000 ppm, hexane ≤ 290 ppm |
| REACH (EC) 1907/2006 | Registration dossier for > 1 tonne/y | Triggers requirement for (αS,4R) specific registration if commercialised in EU |
When integrating the compound into an in vitro blood-brain barrier model based on hCMEC/D3 monolayers (passages 25–35, TEER ≥ 150 Ω·cm2), the apical-to-basolateral permeability coefficient Papp measured at 10 µM donor concentration over 60 min in HBSS buffer containing 4% BSA is reported as 5.9 × 10−6 cm·s−1 (n = 2 independent experiments, no published replicate study available). This value categorises the compound as moderate-to-high permeability by the correlation of Papp with in vivo brain uptake index in mice. Researchers should note that P-glycoprotein efflux liability has not been quantified in bidirectional transport assays under use of the specific P-gp inhibitor GF120918; the absence of those data precludes definitive classification as a CNS-penetrant non-substrate.
