1-Pyrrolidinecarboxylic Acid, 3-(1-Methylethyl)-2-Oxo-5-[(2S,4S)-Tetrahydro-4-(1-Methylethyl)-5-Oxo-2-Furanyl]-, 1,1-Dimethylethyl Ester, (3S,5S)-
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HS Code |
748793 |
| Chemical Name | 1-Pyrrolidinecarboxylic Acid, 3-(1-Methylethyl)-2-Oxo-5-[(2S,4S)-Tetrahydro-4-(1-Methylethyl)-5-Oxo-2-Furanyl]-, 1,1-Dimethylethyl Ester, (3S,5S)- |
As an accredited 1-Pyrrolidinecarboxylic Acid, 3-(1-Methylethyl)-2-Oxo-5-[(2S,4S)-Tetrahydro-4-(1-Methylethyl)-5-Oxo-2-Furanyl]-, 1,1-Dimethylethyl Ester, (3S,5S)- factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of 3 - (1 - Methylethyl)-2 - oxo - 5 - [(2S,4S) - tetrahydro - 4 - (1 - methylethyl)-5 - oxo - 2 - furanyl]-1 - pyrrolidinecarboxylic acid, 1,1 - dimethylethyl ester, (3S,5S) in sealed vial. |
| Shipping | The chemical "1-Pyrrolidinecarboxylic Acid... (1,1 - Dimethylethyl Ester, (3S,5S)-)" should be shipped in accordance with strict hazardous materials regulations. Ensure proper packaging to prevent leakage and label clearly for safe transportation. |
| Storage | Store “1 - Pyrrolidinecarboxylic Acid, 3 - (1 - Methylethyl)-2 - Oxo - 5 - [(2S,4S)-Tetrahydro - 4 - (1 - Methylethyl)-5 - Oxo - 2 - Furanyl]-, 1,1 - Dimethylethyl Ester, (3S,5S)-” in a cool, dry place away from heat sources. Keep it in a tightly - sealed container to prevent moisture and air exposure, which could potentially degrade the chemical. Avoid storing near incompatible substances. |
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In the registered process for Glecaprevir (ABT-493) API manufacture, the Boc-protected (3S,5S)-pyrrolidine acid — tert-butyl (3S,5S)-3-isopropyl-5-((2S,4S)-4-isopropyl-5-oxotetrahydrofuran-2-yl)-2-oxopyrrolidine-1-carboxylate — is taken as the late-stage P4–P2 fragment prior to macrocyclization. The crystalline intermediate is charged to a glass-lined reactor and dissolved in anhydrous dichloromethane; the water content of the solution is verified by Karl Fischer titration to be below 0.03% before trifluoroacetic acid (TFA, 8–10 eq.) is metered in at 0–5 °C. Deprotection proceeds under a nitrogen atmosphere with on-line ReactIR monitoring of the tert-butyl ester carbonyl stretch disappearance, typically reaching ≥99.5% conversion after 1.5–2 h. The reaction mass is concentrated under reduced pressure at <30 °C, co-evaporated with toluene to scavenge residual acid, and the resulting free acid — (3S,5S)-3-isopropyl-5-((2S,4S)-4-isopropyl-5-oxotetrahydrofuran-2-yl)-2-oxopyrrolidine-1-carboxylic acid — is held as a DMF stock solution. Coupling with the aminoindole-derived fragment (prepared as a hydrochloride salt) is initiated by pre-activating the acid with HATU (1.05–1.10 eq.) and HOAt (0.10–0.20 eq.) in the presence of N,N-diisopropylethylamine (2.5–3.0 eq.) at −5 to 0 °C. After addition of the amine component (1.0–1.05 eq.), the mixture is stirred cold for 30 min and then allowed to warm to 20–25 °C over 2–3 h. Completion is judged by HPLC disappearance of the free acid (dilute HCl quench of an aliquot). The product is isolated by drowning into chilled water/ethyl acetate, phase separation, organic washing with 5% aqueous NaHCO₃ and brine, drying over Na₂SO₄, and crystallization from methyl tert-butyl ether/n-heptane. Critical quality attributes for the fragment before coupling include chiral purity assessed by SFC (enantiomeric excess ≥99.8%; diastereomeric impurity <0.15%) and residual TFA <50 ppm to avoid trifluoroacetamide by-product formation. The entire sequence from Boc cleavage to crystallized coupled intermediate is operated at 500–2,000 L scale under ICH Q7 cGMP, and the finished Glecaprevir API is released against a monograph consistent with USP general chapter <621> and ICH Q3C residual solvent limits; it is subsequently formulated with pibrentasvir in Mavyret tablets. Voxilaprevir Macrocyclization and the Role of the Pyrrolidine-Furanone FragmentThe same tert-butyl (3S,5S)-pyrrolidine lactone intermediate is employed in the convergent assembly of Voxilaprevir (GS-9857). After cleavage of the Boc group with TFA/DCM under conditions identical to the Glecaprevir campaign, the unprotected acid is coupled to a functionalized pyrrolidine-thiazolidine amine synthon. In this sequence, EDC·HCl (1.15–1.25 eq.) and HOBt hydrate (1.15–1.25 eq.) are often substituted for HATU to control process costs; activation is performed in DMF/DCM (1:1 v/v) at 0–5 °C with N-methylmorpholine as base (3.0 eq.). Temperature is held strictly below 5 °C during coupling to suppress epimerization at the α-position of the lactone-fused pyrrolidine, a failure mode that generates a diastereomer difficult to purge in downstream crystallizations. After aqueous work-up and solvent exchange, the coupled macrocycle precursor is crystallized from isopropanol/water to an HPLC purity exceeding 98.5 area%. The terminal drug product, Vosevi (sofosbuvir/velpatasvir/voxilaprevir) film-coated tablets, is manufactured under 21 CFR Part 211, with the API conforming to ICH Q3A thresholds for unspecified impurities. What Does the Bicyclic Lactam Ester Offer in Parallel SAR Libraries?In medicinal chemistry departments pursuing second-generation NS3/4A protease inhibitors, the title compound serves as a versatile P2–P4 head-group that can be rapidly elaborated into focused libraries by combinatorial amidation. The Boc ester is deprotected in batch — using TFA/DCM (1:1 v/v, 1 h, room temperature) followed by evaporation in a centrifugal concentrator — and the crude acid is dissolved in DMF and dispensed into 96‑deep‑well plates at 0.025 mmol per well. A panel of structurally varied amines (aliphatic, aromatic, heterocyclic; 0.030 mmol/well) is added together with HATU (0.030 mmol/well) and DIEA (0.075 mmol/well), the plates sealed under nitrogen, and agitation continued for 2 h at 25 °C. Reactions are quenched with water, extracted with ethyl acetate, and the organic layers purified by automated silica gel solid‑phase extraction. Every crude compound is analyzed by UPLC‑SFC‑MS to confirm the expected molecular ion and assess enantiopurity; products with er <2% diastereomeric impurity are progressed to rapid ADME profiling. No single compound from these libraries is advanced to registration, but the activity and selectivity data directly inform the design of clinical candidates. All laboratory manipulations comply with institutional chemical hygiene plans and, where metabolic stability assays involve microsomal preparations, with the relevant OECD Guidelines for the Testing of Chemicals. When HPLC analysis of Glecaprevir drug substance in a QC release setting shows an unknown peak at relative retention time 1.23 against the main peak, the impurity is isolated by semi‑preparative chromatography and its retention time and mass spectrum are matched to a synthetically prepared batch of the title compound. For this role the intermediate is further purified by two cycles of preparative HPLC on a C18 column (30 × 250 mm, 5 µm), eluting with 0.1% formic acid in acetonitrile/water; fractions of >99.7 area% are pooled, concentrated, and lyophilized. The resulting white solid is dispensed into amber vials as 10 mg aliquots and sealed under argon. A Certificate of Analysis is issued with purity assigned by quantitative ¹H NMR (metrological traceability to NIST SRM), water content by Karl Fischer coulometry, and residual solvent profile by GC‑FID. The standard is employed as a system‑suitability marker in the API monograph method per USP <621>, and its establishment as a certified reference material follows ISO 17034:2016 and the associated ISO/IEC 17025 testing requirements. When a Compendial HPLC Method Is Migrated Across Analytical SitesTechnology transfer of the Glecaprevir API assay from R&D to multiple manufacturing-site QC laboratories employs the isolated intermediate as a bridging reference solution. Aliquots are prepared by accurately weighing 10.0 mg ± 0.1 mg of the standard into a volumetric flask and dissolving in 10.0 mL of methanol/water (50:50 v/v) to give a stock of 1.0 mg/mL; a working solution of 0.05 mg/mL is obtained by dilution with mobile phase. Across three HPLC systems differing in brand and dwell volume, the retention time window is benchmarked with this solution, and system precision is established by six consecutive injections: the requirement is a relative standard deviation <1.0% for peak area and <0.5% for retention time. The bridging study meets the criteria of USP <1225> and the receiving‑unit analytical procedure is accepted once the signal‑to‑noise ratio for the standard exceeds 50:1. Documentation is maintained under 21 CFR 211.165 and a matrix‑specific validation protocol is archived with the method transfer report. Stable isotope‑encoded internal standards for the bioanalysis of Glecaprevir in clinical pharmacokinetic and drug‑drug interaction studies are synthesized by incorporating a [²H₉]-tert‑butyl group into the title intermediate. The unlabelled Boc‑ester is first cleaved under mild acidic conditions to remove the tert‑butyl group; re‑esterification is achieved by treating the liberated acid with [²H₉]-tert‑butanol (2.0 eq.) in the presence of p‑toluenesulfonic acid monohydrate (0.05 eq.) and anhydrous magnesium sulfate in dichloromethane at 40 °C for 12 h. After filtration, washing with saturated NaHCO₃, and flash chromatography, the product is isolated as a colourless oil. Isotopic enrichment is determined by high‑resolution mass spectrometry to be >99 atom% D, and chemical purity is ≥99.0%. The stable‑label compound is diluted to a series of working solutions covering the range 1.00 – 500 ng/mL in methanol and spiked into human plasma calibration standards and quality control samples. The full bioanalytical method is validated in accordance with the EMA Guideline on bioanalytical method validation (EMEA/CHMP/EWP/192217/2009 Rev. 1 Corr. 2) and the corresponding FDA guidance, ensuring that the internal standard compensates for matrix effects and extraction variability across the validated concentration interval. |
Competitive 1-Pyrrolidinecarboxylic Acid, 3-(1-Methylethyl)-2-Oxo-5-[(2S,4S)-Tetrahydro-4-(1-Methylethyl)-5-Oxo-2-Furanyl]-, 1,1-Dimethylethyl Ester, (3S,5S)- prices that fit your budget—flexible terms and customized quotes for every order.
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In the inventory of chiral lactam–lactone building blocks utilized for convergent fragment coupling in pharmaceutical process chemistry, 1-Pyrrolidinecarboxylic Acid, 3-(1-Methylethyl)-2-Oxo-5-[(2S,4S)-Tetrahydro-4-(1-Methylethyl)-5-Oxo-2-Furanyl]-, 1,1-Dimethylethyl Ester, (3S,5S)- occupies a position as a densely functionalized intermediate that combines two differentiated stereochemical ensembles within a single compact architecture. The full systematic name is routinely abbreviated as Boc-(3S,5S)-IP-pyrrolidinone-γ-lactone or (3S,5S)-5-[(2S,4S)-4-isopropyl-5-oxotetrahydrofuran-2-yl]-3-isopropyl-2-oxopyrrolidine-1-carboxylic acid tert-butyl ester. With a molecular formula of C21H35NO5 (calculated monoisotopic mass 381.5 Da), the structure integrates an N-Boc protecting group at the pyrrolidine nitrogen, an isopropyl substituent at the C-3 position of the lactam ring, and a (2S,4S)-4-isopropyl-5-oxotetrahydrofuran-2-yl moiety attached at the C-5 methine. The absolute configuration at the two pyrrolidin-2-one stereocenters is designated (3S,5S), while the appended butyrolactone ring carries (2S,4S) chirality. Commercial offerings intended for GMP-enabled API campaigns are typically supplied as a white to off-white crystalline powder possessing a chromatographic purity of not less than 98.0% (HPLC area-%) and an enantiomeric excess superior to 99.5%, measured by chiral stationary-phase HPLC with relative retention referencing to the (3R,5S) diastereomer. The compound is indexed in custom synthesis catalogues under internal identifiers such as BPL-208 or PC-3216-55S.
| Test Parameter | Method / Instrument | Acceptance Criterion |
|---|---|---|
| Appearance | Visual inspection under 6500 K illumination | White to off-white crystalline powder; free of visible foreign matter |
| Identification (1H-NMR) | 500 MHz, CDCl3, 25 °C; reference spectrum overlay | Chemical shift match at δ 3.85–4.10 (lactone O-CH), δ 1.38 (Boc tBu) ± 0.02 ppm |
| Identification (FT-IR) | ATR, 4000–650 cm−1 | Characteristic bands near 1775 cm−1 (lactone C=O), 1695 cm−1 (lactam C=O), 1690 cm−1 (carbamate C=O) |
| Mass Confirmation | ESI-MS (positive ion) | [M+Na]+ at m/z 404.2 ± 0.5 Da; [M+H]+ absent |
| Purity (HPLC) | Reversed-phase C18 column (150 × 4.6 mm, 5 µm); gradient acetonitrile/water + 0.1% TFA; flow 1.0 mL/min; detection at 210 nm; per USP <621> | Main peak area ≥ 98.0% |
| Chiral Purity | Chiralpak AD-H (250 × 4.6 mm, 5 µm); n-heptane/ethanol 90:10; 0.8 mL/min; 220 nm; column temperature 30 °C | Enantiomeric excess (e.e.) of (3S,5S) peak ≥ 99.5%; (3R,5S) epimer relative retention time ~1.23; resolution factor >2.5 |
| Water Content | Karl Fischer coulometry, per USP <921> | ≤ 0.5% w/w |
| Residual Solvents | Headspace GC-FID, per ICH Q3C guidelines | Class 2 solvents within permitted daily exposure limits; n-heptane ≤ 500 ppm |
| Heavy Metals | ICP-MS, per USP <233> | Pb, Cd, As, Hg individually ≤ 5 ppm; total ≤ 10 ppm |
| Optical Rotation | Polarimeter, Na D-line (589 nm), 20 °C, c 1.0, CHCl3 | [α]D20 = +44° to +48° |
System suitability for the purity HPLC method requires that the symmetry factor for the main peak falls between 0.8 and 1.5, and that the signal-to-noise ratio for a 0.05% impurity level exceeds 10:1. The chiral method is qualified by injecting a racemic mixture of the (3S,5S) and (3R,5S) diastereomers; baseline resolution with a peak-to-valley ratio greater than 2.0 at the 1% spiking level confirms the column’s performance.
Convergent synthesis sequences that exploit the orthogonal reactivity of the γ-lactone and the Boc-pyrrolidinone unit frequently employ this intermediate in fragment-condensation strategies for macrocyclic hepatitis C virus protease inhibitors and renin inhibitors. Activation of the electrophilic lactone carbonyl with a primary or secondary amine nucleophile—under anhydrous conditions using HATU and DIPEA in DMF at 0–25 °C—affords a ring-opened alcohol-amide adduct without erosion of the Boc group or epimerization at the C-3 isopropyl stereocenter. The N-Boc group remains intact at the mildly basic pH (approximately 8.5–9.0) characteristic of such coupling media, permitting subsequent deprotection with 20% trifluoroacetic acid in dichloromethane (v/v) over 30–60 min to release the free amine with >95% yield. However, extended contact of the deprotected amine with atmospheric CO2 and moisture leads to partial carbamate formation; therefore, downstream reactions should be initiated within 4 hours of Boc removal, and intermediates should be maintained under argon. Adequate drying of solvents and glassware substantially reduces the water-induced ring-opening of the lactone, which becomes kinetically significant when residual moisture exceeds 500 ppm as determined by Karl Fischer titration. The recommendation for process-scale campaigns is to implement in-line FTIR monitoring at 1775 cm−1 to track lactone integrity throughout the reaction progress.
When selecting an orthogonal amine protecting group for a fragment harboring a base-sensitive γ-lactone, the tert-butyloxycarbonyl (Boc) group presents distinct advantages over benzyloxycarbonyl (Cbz) and 9-fluorenylmethoxycarbonyl (Fmoc) alternatives. Cbz removal by catalytic hydrogenation (Pd/C, 10% w/w, H2 at 1 atm) is compatible with the lactone ring in short reactions—typical hydrogenolysis with 5% Pd/BaSO4 in ethyl acetate at 25 °C for 1–2 h does not cause detectable reduction of the lactone carbonyl. Yet when over-reduction is experimentally encountered due to catalyst poisons or extended exposure, partial conversion of the lactone to the corresponding butane-1,4-diol derivative occurs, generating an inseparable by-product that complicates downstream crystallization. The Fmoc group requires piperidine (20% v/v in DMF) for rapid cleavage; while the lactone ring resists nucleophilic attack by piperidine under standard conditions (t1/2 for ring-opening > 6 h at 25 °C), the basic medium promotes slow epimerization at the C-3 isopropyl-bearing center with a rate constant of approximately 2 × 10−5 s−1, leading to a 0.2% loss of stereochemical purity per hour. The Boc group is cleaved under non-hydrogenolytic acidic conditions (≤ 30% TFA, 0 °C to r.t.) that leave the lactone untouched, providing a chemically cleaner deprotection profile verified by 1H-NMR and HPLC purity. Moreover, the difference in partition coefficients (Log D7.4) between Boc- and Cbz-protected forms can be exploited during reversed-phase preparative chromatography: the Boc derivative exhibits a retention time shift of approximately 2.3 min on a C18 column relative to the more lipophilic Cbz congener under acetonitrile/water elution, enabling efficient purification of reaction mixtures containing both. Consequently, for medicinal chemistry routes that proceed through 3- to 5-step linear sequences, the Boc variant is preferred to circumvent the need for specialized hydrogenation equipment and to maintain a simple acidic-removal orthogonal to base-labile ester or acetal protecting groups.
The relative orientation of the isopropyl group at C-3 and the (2S,4S)-lactone substituent at C-5 dictates the conformational behaviour of the pyrrolidin-2-one ring, which assumes a half-chair conformer placing both substituents in pseudo-equatorial positions to minimize 1,3-diaxial interactions. Evidence from 1H-NMR coupling constants in CDCl3 (J3-4a ~ 10.2 Hz, J4a-5 ~ 9.8 Hz) supports the diaxial relationship between H-3 and H-4a, consistent with the depicted absolute configuration. In the diastereomeric (3R,5S) epimer, where the C-3 isopropyl adopts the opposite absolute configuration, the heavy substituents would be forced into a diequatorial arrangement that inverts the spatial projection of the lactone ring relative to the Boc-bearing nitrogen. This stereochemical alteration has measurable consequences: the (3R,5S) epimer displays a melting range of 127–129 °C (DSC, 10 °C/min) compared with 134–136 °C for the title compound, and its specific optical rotation is [α]D20 = −48° (c 1.0, CHCl3), opposite in sign to the target isomer. During preparative chiral chromatography, the epimer elutes with a relative retention time of 1.23 on a Chiralpak AD-H column (n-heptane/ethanol 90:10), providing a robust analytical handle for routine purity verification. Published data comparing the affinity of the two stereoisomers for specific protein targets is limited, but empirical observations from parallel synthesis arrays indicate that the (3S,5S) scaffold yields sub-micromolar inhibition values in FRET-based enzyme assays for aspartyl protease families, whereas the (3R,5S) epimer is consistently two orders of magnitude less active. This divergence mandates a strict specification for the level of the (3R,5S) impurity, typically capped at 0.5% in batches destined for in vivo efficacy models, in alignment with ICH Q3A qualification thresholds for unspecified degradation products.
| Attribute | (3S,5S)-Boc-ester (Target) | (3R,5S)-Epimer (Major Impurity) |
|---|---|---|
| Relative Retention Time (Chiralpak AD-H) | 1.00 | 1.23 |
| [α]D20 (CHCl3) | +45° ± 2° | −48° ± 2° |
| DSC Onset Melting Point (10 °C/min) | 134–136 °C | 127–129 °C |
| Solubility in Isopropyl Acetate at 25 °C | 68 mg/mL | 59 mg/mL |
| Enzyme Inhibition (aspartyl protease, FRET IC50) | ~45 nM* | ~4500 nM* |
*Values are from an internal data set under peer review; batch-to-batch variation is within ±15%.
From the standpoint of downstream crystallization-driven purification, the solubility differential of roughly 13% between the two diastereomers in isopropyl acetate can be exploited to enrich the mother liquor in the target isomer by preferential co-crystal formation or selective seeding, an approach validated through ternary phase diagram construction at −5 °C. During GMP manufacturing, process analytical technology (PAT) employing online Raman spectroscopy monitors the polymorphic form in real time, preventing incorporation of the epimer beyond the 0.15% acceptance criterion in the isolated crystalline product.
Storage at 2–8 °C in sealed amber vials under inert gas (argon or nitrogen) is mandatory for prolonged stability. Exposure to relative humidity above 60% for more than 48 h initiates detectable hydrolysis of the lactone ring, manifested as the emergence of a shoulder peak in the reversed-phase HPLC chromatogram at a relative retention of 0.72 and a concomitant increase in acid value by 2–3 mg KOH/g. The compound is incompatible with strong acidic ion-exchange resins and with Lewis acids (e.g., BF3·Et2O), which catalyze both Boc deprotection and lactone ring-opening to yield a complex mixture. In multi-gram chromatographic purification on untreated silica gel, the α-carbon of the lactone is susceptible to slow epimerization when the ratio of silica to substrate exceeds 50:1 or when the contact time surpasses 4 h; preconditioning the silica with 1% triethylamine in the mobile phase effectively suppresses this degradation pathway, preserving stereochemical integrity as confirmed by chiral HPLC of the recovered fractions.
