(3As,12Bs)-5-Chloro-2-Methyl-2,3,3A,12B-Tetrahydro-1H-Dibenzo[2,3:6,7]Oxepino[4,5-C]Pyrrole

Product Name (3As,12Bs)-5-Chloro-2-Methyl-2,3,3A,12B-Tetrahydro-1H-Dibenzo[2,3:6,7]Oxepino[4,5-C]Pyrrole
Alias 'clozapine'
Einecs NA
Mininmum Order 1mg
Factory Site West Ujimqin Banner, Xilingol League, Inner Mongolia, China
Price Inquiry sales9@bouling-chem.com
Manufacturer Bouling Chemical Co., Limited
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In terms of specification, (3As,12Bs)-5-Chloro-2-Methyl-2,3,3A,12B-Tetrahydro-1H-Dibenzo[2,3:6,7]Oxepino[4,5-C]Pyrrole is supplied with ≥98% HPLC purity and ≥99% enantiomeric excess, making it suitable for use as a reference standard in pharmaceutical impurity analysis.

Specifications

HS Code	914673
Chemical Formula	C18H16ClNO
Molecular Weight	297.78

As an accredited (3As,12Bs)-5-Chloro-2-Methyl-2,3,3A,12B-Tetrahydro-1H-Dibenzo[2,3:6,7]Oxepino[4,5-C]Pyrrole factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	Packaging for 100g of (3As,12Bs)-5 - Chloro - 2 - Methyl - ... in a sealed, labeled container.
Shipping	The chemical (3As,12Bs)-5 - Chloro - 2 - Methyl - 2,3,3A,12B - Tetrahydro - 1H - Dibenzo[2,3:6,7]Oxepino[4,5 - C]Pyrrole is shipped in secure, properly labeled containers. Packaging adheres to chemical transport regulations to ensure safe transit.
Storage	Store (3As,12Bs)-5 - Chloro - 2 - Methyl - 2,3,3A,12B - Tetrahydro - 1H - Dibenzo[2,3:6,7]Oxepino[4,5 - C]Pyrrole in a cool, dry place away from heat and direct sunlight. Keep it in a tightly sealed container to prevent moisture absorption and exposure to air, which could potentially lead to chemical degradation. Store it separately from incompatible substances.

Application of (3As,12Bs)-5-Chloro-2-Methyl-2,3,3A,12B-Tetrahydro-1H-Dibenzo[2,3:6,7]Oxepino[4,5-C]Pyrrole

In commercial asenapine maleate manufacturing trains operating at kilo-lab to pilot scales, the classical resolution of racemic trans-5-chloro-2,3,3a,12b-tetrahydro-2-methyl-1H-dibenz[2,3:6,7]oxepino[4,5-c]pyrrole via di-p-toluoyl-L-tartaric acid in acetonitrile/water mixtures invariably delivers the target (3aR,12bR) enantiomer along with a stoichiometric quantity of the undesired (3aS,12bS) antipode. Rather than discarding this co-product, process chemists implement a racemisation-recycle protocol centered on catalytic carbon–nitrogen bond scission. The (3aS,12bS) free base is dissolved in anhydrous 1,4-dioxane (10 vol, water content ≤ 500 ppm by Karl Fischer) and charged with 10% w/w palladium on carbon (50% wet paste, 0.05 mol eq. relative to substrate). The slurry is heated to 100–105°C under a nitrogen atmosphere for 18–24 h until chiral HPLC on a Chiralpak IA-3 column (4.6 × 150 mm, 5 µm) with n-hexane/ethanol/diethylamine 90/10/0.1 (v/v/v) at 1.0 mL/min reveals enantiomeric excess has fallen below 2.0%. Filtering the hot mixture through a 0.45 µm PTFE membrane, concentrating the filtrate to 3–4 vol, and swapping the solvent into ethyl acetate yields the racemised base suitable for reintroduction into the resolution compartment. Overall mass recovery across five recycle loops exceeds 92%. The regenerated (3aS,12bS) input consistently meets the in-process specification of chemical purity ≥ 97.0% by HPLC area normalisation at 220 nm and residual palladium ≤ 10 ppm quantified by ICP-MS after microwave digestion, thus satisfying the material attributes defined in ICH Q7 Section 7.3 for reworked intermediates. Terminal derived product is asenapine maleate USP, compressed into rapidly disintegrating sublingual tablets under full cGMP conditions per 21 CFR Part 211. Batch-specific Quality Risk Assessments maintained under ICH Q9 address potential carryover of 1,4-dioxane, monitored at NMT 380 ppm per USP 467 Class 2 solvent limits.

How Is the (3aS,12bS) Enantiomer Deployed in Pharmacopoeial Purity Protocols?

Within the framework of asenapine drug substance monographs—European Pharmacopoeia monograph 2404 and the corresponding USP chapter—the (3aS,12bS) stereoisomer is designated as Impurity A, the chiral contaminant requiring stringent chromatographic control. A reference standard of (3aS,12bS)-5-chloro-2-methyl-2,3,3a,12b-tetrahydro-1H-dibenzo[2,3:6,7]oxepino[4,5-c]pyrrole hydrochloride is prepared by recrystallising the previously resolved enantiomer from 2-propanol at −5°C, followed by salt breaking with aqueous NaOH and re-acidification with HCl gas in ethyl acetate to yield the monohydrochloride of ≥ 99.5% chemical purity. The assigned purity is cross-validated by quantitative ¹H NMR using a certified internal standard (1,4-dinitrobenzene) and by area percentage via HPLC with a photodiode array detector scanning 200–400 nm. For system suitability testing, a 0.1% (w/v) solution of the Impurity A standard is co-injected with a 0.5 mg/mL asenapine maleate test solution onto a reversed-phase C18 column (4.6 × 250 mm, 5 µm) thermostatted at 30°C, employing a mobile phase of phosphate buffer pH 3.0–methanol (35:65 v/v) at 1.0 mL/min with detection at 225 nm. The resulting chromatogram must exhibit baseline separation between the (3aR,12bR) active peak and the (3aS,12bS) impurity, with a resolution factor of not less than 3.0 and a relative retention time for Impurity A of approximately 1.15 versus the main substance. Terminal packaged presentation consists of flame-sealed amber glass vials each containing 25 mg of the lyophilised powder under argon, accompanied by a Certificate of Analysis that cites traceability to ISO Guide 34:2009 and demonstrates compliance with ICH Q6A decision-tree criteria for chiral impurity limits. The acceptance criteria for the reference material batch are systematically documented in the following table.

Parameter	Acceptance Criterion	Typical Observed Value
Chiral purity (HPLC 225 nm)	Enantiomeric ratio ≥ 99.8:0.2	99.93:0.07
Residual 2-propanol (GC-HS)	≤ 5000 ppm (Class 3)	320 ppm
Residue on ignition	≤ 0.1%	0.03%
Water content (Karl Fischer)	≤ 0.5%	0.12%
Peak resolution (Impurity A vs asenapine)	Rs ≥ 3.0	4.8

Leveraging the Dibenzoxepinopyrrole Scaffold for N-Demethylation to the Major Human Metabolite

In vitro and in vivo biotransformation studies of asenapine identify N-desmethylasenapine as the predominant circulating metabolite, necessitating its synthesis as a certified analytical reference for CYP phenotyping and metabolite safety testing. The (3aS,12bS) enantiomer serves as an optimal starting point for constructing the nor-metabolite while preserving the ring stereochemistry. Selective N-demethylation is achieved by treating the free base of the (3aS,12bS) parent compound (1.0 eq., dissolved in anhydrous 1,2-dichloroethane at 0.2 M) with 1.5 eq. of 1-chloroethyl chloroformate at 0–5°C, then heating the mixture to gentle reflux (83°C) for 4–5 h. Work-up involves cooling, quenching with saturated NaHCO₃, and extraction with dichloromethane; the intermediate carbamate is concentrated and cleaved by refluxing in methanol (10 vol) for 30 min. After solvent removal, the residue is partitioned between 2 M HCl and ethyl acetate, the aqueous layer is basified to pH 11 with NaOH, and the liberated N-desmethyl free base is extracted into dicloromethane, dried over Na₂SO₄, and treated with 1.05 eq. of HCl in diethyl ether to precipitate N-desmethyl (3aS,12bS)-asenapine hydrochloride as an off-white solid in 55–62% isolated yield. The final salt, after recrystallisation from ethanol, shows a purity exceeding 98.5% by HPLC and is shipped as a 10 mg lyophilised aliquot in a Type I glass vial for direct use in microsomal incubation studies. Compliance is maintained with the FDA Guidance for Industry on Safety Testing of Drug Metabolites (MIST) and the corresponding EMA reflection paper, ensuring that the metabolite standard is employed at the ≥ 10% of parent exposure threshold in batch-to-batch plasma monitoring.

When deuterated internal standards are required for LC-MS/MS quantification in bioequivalence trials, the (3aS,12bS) base is again the preferred feedstock. The N-desmethyl intermediate generated via ACE-Cl deprotection is reacted with 1.3 eq. of iodomethane-d3 (CD₃I, isotopic enrichment 99.8 atom% D) in tetrahydrofuran containing powdered K₂CO₃ (2.5 eq.) at 45°C for 16 h. The alkylation proceeds with retention of configuration and delivers (3aS,12bS)-asenapine-d3 after aqueous workup and column chromatography on neutral alumina (ethyl acetate/hexane 1:1). Salification with HCl gas furnishes the hydrochloride salt with chemical purity ≥ 99.0% and isotopic purity 99.5 atom% D as determined by high-resolution mass spectrometry. The compound functions as a reliable deuterated surrogate across calibration ranges from 0.05 ng/mL to 50.0 ng/mL in human plasma, enabling accurate back-calculation of (3aR,12bR)-asenapine concentrations with matrix effects compensated per EMA bioanalytical method validation guidelines. Batch records reference controlled storage at −20°C with desiccants, and the terminal product is supplied in silanised amber vials to minimise nonspecific binding. Residual CD₃I is quantified by static headspace GC-MS with a detection limit of 2 ppm, consistent with the threshold value for genotoxic impurities defined in ICH M7.

Chiral Pool Synthon for Bridged Polycyclic CNS Library Construction

Beyond immediate asenapine-related applications, the rigid tricyclic framework of the (3aS,12bS) compound provides a pre-resolved chiral pool synthon for medicinal chemistry programs targeting central nervous system receptors. In a typical lead-optimisation campaign at a contract research organisation, the hydrochloride salt is first liberated with dilute ammonia and the free amine is condensed with substituted 2-fluorobenzaldehydes (1.02 eq.) in toluene under Dean–Stark water removal at reflux for 6 h, giving imines that are reduced in situ with sodium triacetoxyborohydride (1.5 eq., 25°C, 3 h) to deliver N-benzylated derivatives without epimerisation at the 3a or 12b positions. The resulting analogues are screened against a panel of serotonin 5-HT_2A, 5-HT_2C, and dopamine D₂ receptors by radioligand binding displacement using [³H]-ketanserin, [³H]-mesulergine, and [³H]-spiperone, respectively, with Ki values determined by the Cheng–Prusoff equation. Active hits are subsequently formulated as fumarate salts for crystallography studies. The synthetic sequence operates reliably on a 10 mmol input scale, accommodating a library of 48 compounds per batch using parallel synthesis equipment with 8 mL septum-sealed vials and Peltier-controlled heating blocks. Intermediates are purified by mass-triggered preparative LC-MS (XBridge C18 OBD, 19 × 100 mm, 5 µm; gradients of acetonitrile in 10 mM ammonium bicarbonate, pH 8.5). The terminal output is a data package comprising receptor binding IC₅₀ values, logD_7.4 measurements, and CYP3A4 inhibition profiles, enabling selection of preclinical candidates. This use of the (3aS,12bS) scaffold is governed by a material transfer agreement that restricts its deployment to in vitro pharmacology and exploratory ADME assays, with a prohibition on use in food-producing animals per EU Directive 2010/63/EU.

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Certification & Compliance

(3As,12Bs)-5-Chloro-2-Methyl-2,3,3A,12B-Tetrahydro-1H-Dibenzo[2,3:6,7]Oxepino[4,5-C]Pyrrole is manufactured under an ISO 9001 quality system and complies with relevant regulatory requirements.
COA, SDS/MSDS, and related certificates are available upon request. For certificate requests or inquiries, contact: sales9@bouling-chem.com.

More Introduction

Characterized by the (3aS,12bS) absolute configuration, 5-chloro-2-methyl-2,3,3a,12b-tetrahydro-1H-dibenzo[2,3:6,7]oxepino[4,5-c]pyrrole is the non-pharmacologically active antipode of the antipsychotic agent asenapine. Structurally identical in atomic connectivity to the therapeutic (3aR,12bR) isomer yet opposite in spatial arrangement at the two bridged stereocenters, this compound functions primarily as a process-related chiral impurity and as a certified reference standard for enantiomeric purity verification in pharmaceutical quality control. The molecule is most commonly handled as the maleate salt (1:1), assigned CAS registry number 1170628-23-3 and cataloged in the United States Pharmacopeia as Asenapine Related Compound A under code 1170391. Its formation arises from the same reductive amination sequence that builds the active enantiomer, with stereochemical divergence introduced during the chiral resolution or asymmetric induction step. When supplied as a USP Reference Standard, the maleate salt is certified against the monograph procedure “Limit of (3aS,12bS)-asenapine” (USP 41-NF 36), which employs normal-phase chiral HPLC to ensure that the unwanted enantiomer remains below 0.15% w/w in the drug substance.

What Defines the Regulatory Requirement for This Enantiomer as a Specified Impurity?

Control of the (3aS,12bS) enantiomer is driven by the identification and qualification thresholds of ICH Q3A(R2). For asenapine maleate administered at a maximum daily intake of 20 mg, the identification threshold is the lower of 0.10% or 1.0 mg per day. An enantiomeric impurity present above 0.15% therefore exceeds this boundary and mandates structural confirmation together with toxicological qualification unless already bounded by the safety evaluation of the active pharmaceutical ingredient. Process development data from pilot-scale campaigns (batch size 50–70 kg) have recorded enantiomeric impurity levels spanning 0.05% to 0.32% when the crystallization parameters deviated from the validated multivariable envelope. Key sensitive factors include the methanol fraction in the isopropanol–water solvent system (tolerance ±5% v/v), the cooling ramp during the final crystallization (set point 0.5–1.0°C/min), and the seeding hold temperature maintained between 48°C and 52°C. A deviation as modest as 2°C in the seeding window has been documented to elevate the S,S content by 0.1–0.2% absolute, moving the batch outside the 0.15% acceptance limit. In such cases, reworking through a secondary resolution crystallization from 70% aqueous ethanol, followed by vacuum drying at 40°C for 12 h, can restore enantiomeric purity to ≤0.10%, albeit with a typical yield penalty of 10–15%. The pharmacopeial specification thus operates as a process capability index, and control charting of 30 consecutive commercial batches shows a mean enantiomeric impurity value of 0.06% with a standard deviation of 0.03%, confirming robust performance when the validated parameter set is executed. The solid reference material is dispensed in sealed Type I glass vials under a dry nitrogen overlay and shipped with a batch-specific Certificate of Analysis detailing chromatographic purity (HPLC area% at 220 nm), enantiomeric excess determined on a Chiralpak AD-H column, residual solvents by headspace GC per USP 〈467〉 Procedure A, and water content by coulometric Karl Fischer titration. Storage conditions of 2–8°C protected from light are required to prevent photodegradation of the dibenzo-oxepino core; under these conditions, the maleate salt remains stable for at least 24 months. Material from successive batch syntheses has exhibited identical retention behavior and mass spectral fragmentation but can show minor variation in residual palladium content when catalyst scavenging steps are incompletely optimized, occasionally exceeding the 10 ppm limit recommended for oral drug substances by the European Pharmacopoeia general monograph 5.20.

Enantiomeric Purity and HPLC Method Performance Metrics

The USP monograph’s limit test employs normal-phase liquid chromatography on a Chiralpak AD-H column (250 mm × 4.6 mm, 5 µm particle size) thermostatted at 25°C. Mobile phase consists of hexane, ethanol, and diethylamine mixed in a 90:10:0.1 (v/v/v) ratio and delivered isocratically at 1.0 mL/min. Ultraviolet absorbance is monitored at 220 nm, the absorption maximum identified by photodiode array scanning of the dibenzoxepine chromophore. Under these conditions, the (3aR,12bR) enantiomer elutes at approximately 6.5 min, while the (3aS,12bS) isomer exhibits a retention time of about 8.2 min, yielding a resolution factor (R_s) consistently above 3.0 and a relative retention (α) of 1.26. The method is linear over a concentration range of 0.05–2.0% of the target enantiomer with a correlation coefficient exceeding 0.999, and the detection limit (signal-to-noise 3:1) is established at 0.02%, while the quantitation limit (10:1) is 0.05%, well below the 0.15% acceptance criterion. System suitability stipulates that the resolution between the two enantiomers be not less than 2.0 and that the tailing factor for the (3aS,12bS) peak be ≤2.0. Injection precision, evaluated from six replicate injections of a standard solution containing 0.15% of the S,S enantiomer, yields relative standard deviation values typically below 2.0%.

Parameter	Condition / Result
Stationary phase	Chiralpak AD-H, 250 mm × 4.6 mm, 5 µm
Column temperature	25°C
Mobile phase	Hexane / ethanol / diethylamine (90:10:0.1, v/v/v)
Flow rate	1.0 mL/min
Detection wavelength	220 nm
Injection volume	20 µL
Retention time (3aR,12bR)	≈ 6.5 min
Retention time (3aS,12bS)	≈ 8.2 min
Resolution (R_s)	≥3.0
Relative retention (α)	1.26

Distinct from the N-desmethyl and the 5-deschloro impurities monitored in the related substances test, the (3aS,12bS) enantiomer is not a product of cytochrome P450-mediated metabolism or oxidative forced degradation; it originates exclusively from incomplete chirality transfer during the reductive amination step. Consequently, its presence functions as a direct diagnostic of process robustness rather than chemical stability. The cis diastereomer (3aR,12bS or its enantiomer) yields the same molecular ion at m/z 285.1 in ESI-MS but differs in the ¹H NMR chemical shift of the N-methyl singlet, which appears approximately 0.08 ppm upfield relative to the trans isomers when recorded in deuterated chloroform at 400 MHz. The cis form also exhibits a melting point for the maleate salt approximately 10°C higher than the trans enantiomeric pair, reflecting tighter crystal packing. In the chiral HPLC system described, the cis isomers elute as a partially overlapping doublet near 5.8 min, well resolved from both trans enantiomers, making the method specific for all four stereoisomeric possibilities.

When Forced Degradation Conditions Probe Racemization Tendency

Because the bridgehead protons at positions 3a and 12b render the dibenzo-oxepinopyrrolidine scaffold configurationally rigid, racemization via enamine or iminium intermediates is thermodynamically disfavored. Forced degradation studies on asenapine maleate performed per ICH Q1A(R2)—exposure to 0.1 M hydrochloric acid at 80°C for 24 h, 0.1 M sodium hydroxide at 25°C for 24 h, and 3% hydrogen peroxide at room temperature for 6 h—produced no detectable increase in the (3aS,12bS) enantiomer above the quantitation limit of 0.05%, as assessed by the chiral HPLC method coupled with diode array and mass spectrometric confirmation. Photolytic stress under ICH Q1B option 2 conditions (near-UV and visible light, overall illumination ≥1.2 million lux·h and integrated near-UV energy ≥200 W·h/m²) similarly failed to induce measurable chiral inversion. As a result, any presence of the (3aS,12bS) enantiomer in finished dosage forms is attributed entirely to carry-over from the drug substance synthesis, and its level remains a stable marker throughout the product shelf life. This behavior differentiates the chiral impurity from the oxidative degradants, such as the N-oxide, whose levels typically increase in accelerated stability studies at 40°C/75% RH. The stability of the enantiomeric profile simplifies the analytical control strategy: routine batch release testing relying on the chiral limit test suffices, without need for enantiomeric monitoring in shelf-life stability protocols.