(S)-2-(4-Methyl-1,4-Diazepane-1-Carbonothioyl)-N-(2-Methyl-4-(1-Methyl-1,4,5,10-Tetrahydrobenzo[B]Pyrazolo[3,4-E][1,4]Diazepine-5-Carbonyl)Benzyl)Pyrrolidine-1-Carboxamide

During the manufacture of a fused tricyclic pyrazolo-diazepine-based soluble guanylate cyclase (sGC) stimulator intended for once-daily oral administration, process analytical technology (PAT) monitoring of the (S)-pyrrolidine carboxamide-thioamide coupling stage identified a critical dependence of the diastereomeric excess on the addition sequence and the non-aqueous basicity of the medium. The title compound is charged as the electrophilic acyl-thioamide donor at 1.05–1.10 eq relative to the 4-aminomethyl-benzoyl fragment, with the condensation executed in 2-methyltetrahydrofuran (2-MeTHF) under Schlenk-vacuum–backfilled nitrogen at −15 ± 3 °C. Process mass intensity (PMI) evaluations against the ACS Green Chemistry Institute Pharmaceutical Roundtable benchmark confirm that sustained jacket temperature control within this window suppresses bis-acylated impurity F (retention time relative retention 0.87 vs. target) below the ICH Q3A qualification threshold of 0.15%. Regulatory reference: compliance with 21 CFR 210 & 211 for current Good Manufacturing Practice is demonstrated through cleaning validation protocols executed on a Hastelloy C-22 5,000-litre glass-lined reactor train equipped with a Sulzer Chemtech SMVP-type structured packing in the overhead rectification section for solvent recovery. Downstream processing incorporates a pH-swing extraction into 0.5 M citrate buffer (pH 5.5), followed by charcoal treatment with Norit CA1 (5% w/w on crude) to scavenge colloidal palladium residues derived from an earlier Heck coupling. The fully isolated intermediate, after seeding with 0.2 wt% of target crystal form A1, yields a free-flowing white crystalline solid suitable for the final amide bond formation that affords the API intermediate monomesylate salt.

What Drives Regioselective Functionalization at the Pyrazole C-3 Position During BET Bromodomain Inhibitor Assembly?

In programs targeting the acetyl-lysine binding pocket of BRD4(1), the benzopyrazolo-diazepine segment of the title compound serves as a conformationally restricted kinase-hinge-like warhead. Acetyl-lysine mimicry is retained only when the C-3 methyl substituent on the pyrazole ring remains intact; accessibility to the WPF shelf hydrophobic pocket necessitates a 5.2–5.6 Å distance between the diazepine nitrogen and the terminal pyrrolidine carbonyl, a metric verified by small-molecule X-ray crystallography (resolution ≤ 1.8 Å) deposited in the Cambridge Structural Database. Process chemistry batches introduce the chiral pyrrolidine-thioamide portion via a carbonyldiimidazole (CDI)-activated mixed anhydride protocol conducted in anhydrous N,N-dimethylacetamide (DMAc) with a measured water content ≤ 200 ppm by Karl Fischer titration. The addition ratio is stringently held at 0.98–1.02 eq of CDI per free acid equivalent; exceeding 1.05 eq generates an N-acylurea by-product that co-crystallises during the subsequent acetonitrile/water (7:3 v/v) drown-out precipitation, elevating the total-related-substances profile above the USP ⟨1086⟩ threshold for unidentified impurities. Occupational exposure banding aligns with ICH Q3D for Class 1 elemental impurities, with special attention to residual palladium (limit ≤ 10 ppm) and copper (limit ≤ 300 ppm), quantified by ICP-MS against matrix-matched standards prepared in 5% nitric acid. The resultant penultimate intermediate is telescoped directly into a hydrogenolysis in tetrahydrofuran/methanol (1:1) over 5% Pd/Al2O3 (water-wet, 10 wt% loading) at 1 bar H2, and after a 0.2 µm PTFE membrane filtration, the free base is liberated and used for the final conjugate addition to the dimethyl amine warhead of the BRD4 degrader.

Neurokinin-1 Receptor Antagonist Intermediate: Crystallization-Induced Diastereomeric Enrichment Under ICH Q11 Control

For a second-generation NK1 antagonist administered as a transmucosal film, the title chiral centre at the pyrrolidine C-2 position is exploited as the stereochemical origin for the entire pharmacophore. Early campaign data from a 1000-litre cryogenic reactor revealed that a simple rectification of the protecting-group strategy from tert-butyloxycarbonyl (Boc) to acetyl (Ac) altered the eutectic composition of the diastereomeric pair during anti-solvent crystallisation with n-heptane/methyl tert-butyl ether (MTBE) (1:2 v/v), boosting the diastereomeric ratio from 97:3 to 99.8:0.2 without recourse to chiral stationary-phase chromatography. The key downstream operation is a catch-and-release protocol on silica-bound sulfonic acid (SCX-2) columns (loaded at 20 g/L of crude), which removes the unreacted amine component and conserves the thioamide moiety against hydrolytic degradation. Process validation executed against Ph.Eur. 2.2.46 (chromatographic separation) and Ph.Eur. 5.17.1 (recommendations on dissolution testing for immediate-release solid oral dosage forms) confirmed that residual isopropyl acetate, the final crystallisation solvent, was consistently below 5000 ppm, in compliance with ICH Q3C Class 3 residual solvent limits. The addition ratio of the title intermediate to the second amine fragment in the capping step is 1.00–1.05 eq, with the slight excess scrupulously purged by an aqueous 1,4-diazabicyclo[2.2.2]octane (DABCO) wash (3% w/w in water, 2 × reactor volume), a technique that reduces trace acylating species to below the LC-MS/MS detection limit of 1 ng/mL in the final API.

Observations from three consecutive pilot campaigns for a highly soluble dimeric IDO1/TDO dual inhibitor underscore an operational boundary that is often underestimated during scale-up: the DABCO-derived scavenging step described above must be executed within 60 minutes of the final aqueous quench when the ambient relative humidity exceeds 55%. Extended hold times (> 90 min) under such conditions catalyse a thioamide-to-oxoamide hydrolysis whose rate constant was measured at (3.8 ± 0.2) × 10⁻⁴ min⁻¹ at 22°C in wet DMAc. The resulting oxoamide impurity, an ATCC-strain inactive analogue, is not rejected by the terminal anti-solvent crystallisation and co-precipitates at 1:1 stoichiometry with the target molecule. Therefore, when manufacturing sites without humidity-controlled charging suites undertake this transformation, a jacket temperature ramp to 38°C and a nitrogen sweep at 0.5 vessel volumes per minute are employed to drive the water mass fraction in the headspace below 5 g/m³ before the DABCO wash is initiated. Compliance with ICH Q7 Section 8.3 ensures batch homogeneity through a real-time ReactIR 702L probe tuning for the 1670 cm⁻¹ C=O stretch of the desired thioamide versus the 1725 cm⁻¹ signal of the oxoamide degradation product. The final terminal product, a directly compressible granulate with a mean particle size D90 ≤ 250 µm, is formulated into a 50 mg potency film-coated tablet via roller compaction at 3.5 kN/cm and a 0.6 mm screen, meeting dissolution specification Q = 80% at 30 min in 0.01 N HCl according to USP Apparatus II at 50 rpm.

When Thiourea Organocatalysis Requires a Pseudo-C₂-Symmetric Chiral Pocket That Resists Oxidative Racemisation

In the enantioselective Michael addition of dimethyl malonate to trans-β-nitrostyrene catalysed by tertiary amine-thiourea systems, the title compound is employed as the pre-organocatalyst framework after quantitative cleavage of the benzopyrazolo-diazepine carbonyl portion and subsequent reprotection of the resultant secondary amine with 3,5-bis(trifluoromethyl)phenyl isothiocyanate. Under the reductive aminolysis conditions — zinc dust (10 eq) in acetic acid/THF (1:5) at 50°C — the (S)-pyrrolidine carboxamide linker survives with ≥ 98% retention of configuration, as confirmed by chiral SFC on a Chiralpak AD-H column (mobile phase: CO₂/isopropanol 70:30, 2.0 mL/min). The catalyst loading in the model Michael reaction is 5 mol%, providing the (S)-adduct in 89% isolated yield and 93% ee, benchmarked against ISO 17025-accredited in-house enantiopurity protocols. Downstream, the organocatalyst is recovered via solvent switch to tert-butyl methyl ether and precipitation as the hydrochloride salt, which is filtered through a Nutsche filter-dryer with 10 µm PTFE cloth and dried at 40°C/10 mbar for 8 hr. The recovered catalyst retains 91% of its original activity after five recycles, the gradual activity decline being attributable to N-oxidation at the 1,4-diazepane moiety; addition of 0.1 wt% BHT (IUPAC 2,6-di-tert-butyl-4-methylphenol) to the reaction medium extends catalyst half-life to 12 cycles, as quantified by reaction calorimetry (heat flow ≤ 65 W/kg). Occupational health exposure limits for free thiourea species are derived from DNEL assessments under REACH (EC) No 1907/2006, and the slurry handling is performed in an isolator rated OEB 4 (occupational exposure band) per ASTM E2500-20 guidance for containment verification.

Catalytic hydrogenolysis of the benzyl protecting group installed at the terminal 4-aminomethyl position constitutes the final transformation before the compound enters secondary medicinal chemistry interrogation as a fragment-elaborated degrader of the von Hippel-Lindau (VHL) E3 ligase. Within the VHL context, the pyrrolidine carboxamide spacer between the VHL ligand and the target-protein recruiting moiety must maintain a rigid trans-amide geometry with a dihedral angle (Cα–N–C=O) of 168 ± 5°; conformational slip to the cis rotamer, which amounts to ~3% at equilibrium in DMSO-d6 at 25°C, abolishes ternary complex formation as measured by TR-FRET at 1 µM concentration. Large-scale hydrogenation in a Büchi Glas Uster 10-litre Hastelloy autoclave employs 10% Pd/C (50% water-wet, 5 wt% loading) under 3 bar H₂ in ethanol/water (7:3) at 45°C. The raw reaction stream is passed through a Zeta Plus depth filter (grade 30SP) followed by a 0.2 µm nylon membrane to remove catalyst fines, and the resulting colourless filtrate is concentrated to ~15% of original volume before addition to n-heptane for precipitation. Regulatory alignment with 21 CFR 211.110 (sampling and testing of in-process materials) is confirmed through a statistically meaningful in-process control sampling plan covering n = 10 points across the batch, ensuring lot-to-lot uniformity within RSD ≤ 1.5% for the key hydrogenolysis intermediate.