Tert-Butyl(2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2-D]Imidazol-9-Yl)-1H-Imidazol-2-Yl)-4-(Methoxymethyl)Pyrrolidine-1-Carboxylate

Product Name Tert-Butyl(2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2-D]Imidazol-9-Yl)-1H-Imidazol-2-Yl)-4-(Methoxymethyl)Pyrrolidine-1-Carboxylate
Alias PLA-685
Mininmum Order 1 mg
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, Tert-Butyl(2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2-D]Imidazol-9-Yl)-1H-Imidazol-2-Yl)-4-(Methoxymethyl)Pyrrolidine-1-Carboxylate is supplied with ≥98% HPLC purity and ≥99% diastereomeric excess, making it suitable for use as an advanced intermediate in Glecaprevir synthesis.

Specifications

HS Code	822959
Chemical Name	Tert-Butyl (2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2-D]Imidazol-9-Yl)-1H-Imidazol-2-Yl)-4-(Methoxymethyl)Pyrrolidine-1-Carboxylate

As an accredited Tert-Butyl(2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2-D]Imidazol-9-Yl)-1H-Imidazol-2-Yl)-4-(Methoxymethyl)Pyrrolidine-1-Carboxylate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

Packing & Storage

Packing	100 g of Tert - Butyl (2S,4S) - 2 - (... ) - 1 - Carboxylate in a sealed chemical - grade container.
Shipping	Shipping of the chemical "Tert - Butyl (2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2 - D]Imidazol-9 - Yl)-1H - Imidazol-2 - Yl)-4-(Methoxymethyl)Pyrrolidine-1 - Carboxylate" must follow strict regulations for hazardous or specialized chemicals, ensuring proper packaging, labeling, and handling during transit.
Storage	Store the chemical tert - Butyl (2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L - Valyl)-5 - Methylpyrrolidin - 2 - Yl)-1,11 - Dihydroisochromeno[4,3:6,7]naphtho[1,2 - D]Imidazol - 9 - Yl)-1H - Imidazol - 2 - Yl)-4-(Methoxymethyl)pyrrolidine - 1 - Carboxylate in a cool, dry place away from direct sunlight and heat sources. Keep it in a tightly sealed container to prevent exposure to air and moisture, which could potentially degrade the compound.

Application of Tert-Butyl(2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2-D]Imidazol-9-Yl)-1H-Imidazol-2-Yl)-4-(Methoxymethyl)Pyrrolidine-1-Carboxylate

Within cGMP-regulated production of Velpatasvir Active Pharmaceutical Ingredient (API), the title compound is positioned as the penultimate intermediate in a convergent, stereocontrolled assembly. The intermediate carries a Boc-protected pyrrolidine at the imidazole 2-position and a fully elaborated methoxycarbonyl-L-valyl (Moc-Val) substituent on the opposing pyrrolidine; this architecture permits a modular final deprotection–acylation sequence that minimises the co-formation of homodimeric by‑products with retention times ≤0.18 minutes relative to the API peak on reversed-phase HPLC. For commercial batches meeting ICH Q7 Section 7.30 requirements, the receiving acceptance criterion for chromatographic purity is set at ≥98.5% area normalisation (310 nm, C18 column 150 × 4.6 mm, 3.5 µm, gradient 40–95% B over 25 min), with the diastereomeric impurity (C‑2 epimer of the Moc‑Val residue) capped at ≤0.50%. The subsequent N‑Boc cleavage proceeds under strictly anhydrous conditions: a dichloromethane solution (10–12 volumes) is treated with trifluoroacetic acid (4.0–5.0 equivalents) while the jacket temperature of the glass‑lined reactor is controlled to keep the internal mass at −5°C to +5°C. A deviation above +8°C triggers a measurable increase in the (R)-epimer above the 0.15% critical process parameter alert limit. After 2.0–3.5 hours, complete consumption is confirmed by TLC (silica gel 60 F254, EtOAc/hexane 3:7), and the volatiles are removed with a wiped‑film evaporator at a jacket temperature not exceeding 35°C. The resulting amine is telescoped into an amide‑coupling step employing (methoxycarbonyl)-L‑valine N‑hydroxysuccinimide ester (1.20–1.35 molar equivalents) and diisopropylethylamine (3.0 equivalents) in DMF (8 volumes) at 20 ± 3°C for 12–18 hours. After an acidic quench and extraction into methyl tert‑butyl ether, the crude Velpatasvir is concentrated and crystallised from MTBE/n‑heptane (1:4 v/v). Final salt formation with sulfuric acid in ethanol, followed by seeding, furnishes Velpatasvir hemi‑sulfate with chemical purity ≥99.5%, chiral purity by SFC on Chiralpak IA‑3 ≥99.8% enantiomeric excess, total aerobic microbial count ≤100 CFU/g, and residual solvents within USP 〈467〉 Option 2 limits. The entire sequence is executed under ICH Q7 Chapter 8 production controls to ensure batch‑to‑batch traceability of the starting chiral pool.“Granulation Endpoint and Blend Uniformity in Epclusa® Tablets: When the Boc-Protected Intermediate Dictates Crystallinity Control”The physical form and impurity fingerprint of Velpatasvir synthesized from this advanced intermediate exert a measurable influence on the critical material attributes of the fixed‑dose combination tablet Epclusa® (sofosbuvir 400 mg / velpatasvir 100 mg). During the drug product module 3.2.P.2 development, API lots originating from the title compound that contained residual palladium above 8–10 ppm—carried over from the convergent synthesis of the isochromenonaphthoimidazole core via a Suzuki‑type coupling—exhibited a statistically significant increase in N‑nitrosamine surrogate formation under accelerated conditions (40°C/75% RH for 6 months), measured by LC‑HRMS with a quantitation limit of 0.03 ppm. Consequently, the intermediate specification was supplemented with a palladium threshold of ≤5 ppm by ICP‑MS in compliance with EMA Questions and Answers on nitrosamines. Wet granulation for Epclusa® is performed in a top‑driven high‑shear mixer (Gral or equivalent, bowl volume 300 L) with an impeller speed of 120–150 rpm and a chopper at 1500 rpm. The intragranular blend comprises sofosbuvir, velpatasvir, mannitol, microcrystalline cellulose, and croscarmellose sodium in a ratio that delivers a content uniformity of 95–105% label claim with a relative standard deviation ≤4.0% across 10 stratified dosage‑unit samples per USP 〈905〉. Water addition is precisely controlled at 22–25% w/w of dry powder mass to reach a torque endpoint of 12–15 Nm; over‑wetting leads to a bimodal particle size distribution that shifts the d₉₀ above 900 µm and retards dissolution at the 15‑minute time point in 0.5% SLS medium at 37°C, paddle 75 rpm (USP Apparatus 2). Lubrication with sodium stearyl fumarate (1.0% w/w) is carried out in a bin blender for 15 minutes at 25 rpm; the lubricant‑sensitive API particles formed by the original crystallization from MTBE/heptane undergo negligible attrition when the intermediate‑sourced velpatasvir exhibits a plate‑like crystal habit with an aspect ratio ≤3, whereas needle morphologies (aspect ratio ≥8) generate fines that elevate the unconfined yield strength above 2.5 kPa during tableting on a rotary press at 40–60 rpm with a main compression force of 12–18 kN, requiring compression profiles within 1.2–1.8% porosity to avoid capping at ejection.Reference standard qualification for the pharmacopeial monograph of Velpatasvir mandates a fully characterised process impurity marker derived from the penultimate intermediate. The title compound, when subjected to controlled acidic stress—1.0 mL of TFA in 50 mL dichloromethane at 25°C for 6 hours—generates the des‑Boc pyrrolidine amine as the primary anchor impurity, which is subsequently isolated by semi‑preparative HPLC on a C18 column (250 × 20 mm, 10 µm) using a shallow gradient of 0.2% formic acid in water/acetonitrile (flow rate 18 mL/min). Collected fractions are lyophilised, and the lyophilisate is characterised by ¹H‑NMR (600 MHz, DMSO‑d₆) and ¹³C‑NMR to confirm the absence of the tert‑butyl signals at 1.35 and 1.42 ppm. A certified reference standard batch must comply with ISO 17034:2016 Section 7.5 and be accompanied by an uncertainty budget encompassing chromatographic repeatability, balance linearity, and moisture content determined by Karl Fischer coulometry (residual water ≤0.5% w/w). Further photolytic treatment of a methanolic solution exposed to UV‑A (365 nm, 200 W·h/m²) and visible light per ICH Q1B Option 2 yields an oxidative de‑arylation product whose mass increment of +16 amu is confirmed by HR‑ESI‑TOF; this impurity is purified by SFC on a Chiralcel OD‑H column (250 × 21 mm, 5 µm) with a CO₂/methanol mobile phase (80:20) at 40°C and a back‑pressure of 120 bar. The two impurities are incorporated into a system suitability mixture that resolves all components with a minimum resolution factor ≥2.5, thereby enabling the validated related‑substances HPLC method to comply with the ICH Q3A(R2) reporting threshold of 0.05% for a 200 mg daily dose. The table below summarises the impurity markers traceable to the Boc‑protected intermediate.

Impurity Designation	Relative Retention Time (HPLC)	Exact Mass [M+H]⁺	Acceptance Limit (% a/a)
Des‑Boc pyrrolidine amine	0.72	691.32	≤0.15
Moc‑Val C‑2 epimer	0.88	895.44	≤0.50
(S)-Pyrrolidine‑2‑carboxylic acid amide (hydrolysis by‑product)	0.55	525.27	≤0.10
Photo‑oxidative N‑oxide (UV‑A degradation)	1.15	911.43	≤0.10

Combinatorial diversification of the NS5A inhibitor scaffold frequently employs the title compound as a late‑stage common intermediate because the orthogonal protection of the amine functionalities allows sequential, high‑yielding acylations without tedious intermediate purification. In a typical library enumeration aimed at profiling genotype 3a replicon potency, the Boc group is removed with TFA in CH₂Cl₂ at 0°C within a 96‑well reactor block using Teflon‑septum caps, and the resulting crude amine is distributed into pre‑weighed vials containing a set of 24 structurally diverse carboxylic acid building blocks activated as pentafluorophenyl esters. Each acylation is performed in DMF with 2.5 equivalents of DIPEA at ambient temperature for 16 hours under argon. After scavenging excess active ester with aminomethyl polystyrene resin (3.0 equivalents, 2 hours), the library members are purified by automated mass‑directed preparative LC‑MS using a Waters XBridge C18 OBD column (19 × 100 mm, 5 µm) with a 10‑minute gradient of 0.1% NH₄OH in acetonitrile/water at pH 9.5. Purity acceptance for biological testing is set at ≥95% UV‑area (220‑350 nm scan). The terminal products are screened in a transient HCV sub‑genomic replicon assay (genotypes 1a, 1b, 2a, 3a, 4a) with EC₅₀ determinations by quantitative luminescence at 72 hours. The structure–activity relationships generated from this parallel synthesis indicate that replacement of the Moc‑Val motif with bulkier carbamate substituents at the secondary pyrrolidine nitrogen elevates metabolic stability in human liver microsomes (t_1/2 increase from 48 min to 85 min) but attenuates genotype 3a potency by 2‑ to 5‑fold, underscoring the necessity of the discrete stereo‑array preserved in the advanced intermediate for pan‑genotypic coverage.“Can the Scalable Buchwald‑Hartwig Coupling Be Adapted to Multi‑Kilogram Batch Sizes?”When the intermediate is manufactured on a contract development and manufacturing organisation (CDMO) campaign exceeding 15 kg, the pivotal connection between the isochromenonaphthoimidazole core and the pyrrolidine‑imidazole fragment demands rigorous engineering of the C–N cross‑coupling step. The reaction originally developed at gram scale employs tris(dibenzylideneacetone)dipalladium(0) (2.0 mol%) and 2‑dicyclohexylphosphino‑2′,4′,6′‑triisopropylbiphenyl (XPhos, 4.0 mol%) with cesium carbonate (2.0 equivalents) in 1,4‑dioxane at 95°C for 18 hours. During kilo‑lab execution, the heterogeneous nature of the Cs₂CO₃ base in the non‑polar solvent creates a mass‑transfer limitation that extends the induction period and increases the risk of protodebromination of the aryl bromide precursor. Substituting the base with sodium tert‑pentoxide (1.5 equivalents) and switching to a toluene/dimethoxyethane (4:1) mixture reduces the cycle time to 8–10 hours while maintaining a conversion of ≥97%. In a 100 L Hastelloy C‑22 reactor, the exotherm upon catalyst activation is controlled by a stepwise temperature ramp: the jacket is heated from 25°C to 65°C at 0.5°C/min, held at 65°C for 30 minutes until the self‑accelerating phase subsides, then ramped to 95°C at 0.3°C/min. The palladium scavenging protocol following coupling is critical because the Boc protecting group is susceptible to cleavage by residual acidic species generated during metal removal. A two‑stage filtration through a Celite pad doped with activated carbon (Si‑Thiol functionalised silica, 5 wt% relative to crude product) followed by extraction with an aqueous 5% N‑acetyl‑L‑cysteine solution at pH 7.2 reduces palladium from 120–180 ppm to ≤5 ppm. The table below contrasts key performance parameters across laboratory and pilot‑plant runs when this advanced synthetic strategy is employed.

Parameter	Laboratory (0.5‑1.0 kg)	Pilot Plant (15‑20 kg)
Reactor material	Glass, 3‑neck round‑bottom	Hastelloy C‑22, 100 L
Agitation rate (tip speed)	0.8 m/s	2.5 m/s (pitched‑blade impeller)
Catalyst loading	Pd₂(dba)₃ 2.0 mol%	Pd₂(dba)₃ 1.2 mol%
Base system	Cs₂CO₃, 2.0 equiv	NaO‑t‑amylate, 1.5 equiv
Solvent	1,4‑Dioxane	Toluene/DME 4:1
Reaction time at 95°C	18 h	8.5 h
Residual Pd post‑workup	<10 ppm	≤3 ppm
Isolated yield (corrected)	81%	78%
Chromatographic purity	99.1%	98.8%

The fully isolated advanced intermediate at pilot scale is dispensed in amber glass containers under argon overlay, stored at −20°C ± 5°C, and assigned a retest period of 36 months when stability data per ICH Q1A(R2) confirm no trend in purity or moisture beyond the 0.3% two‑tailed confidence interval. A dedicated quality agreement between the CDMO and the sponsor stipulates that the batch certificate must list the c = 0, n = 1 acceptance sampling plan for the diastereomeric impurity per ISO 2859‑1:1999 and include the enantiomeric excess determined on a Chiralpak IC column (250 × 4.6 mm, 5 µm) with a mobile phase of n‑hexane/ethanol/methanesulfonic acid (75:25:0.1) at 1.0 mL/min. The resulting Velpatasvir API manufactured from these batches consistently meets the specifications for sulfated ash (≤0.1%) and heavy metals (≤10 ppm) outlined in the European Pharmacopoeia monograph draft for Velpatasvir sulfate, enabling straightforward compilation of the impurity appendix in the marketing authorisation application.System suitability testing for the validated HPLC‑UV method used to release Velpatasvir drug substance incorporates a forced‑degradation mixture prepared directly from the title intermediate. An aliquot of the intermediate is exposed to 3% hydrogen peroxide at 25°C for 4 hours to generate the imidazole‑N‑oxide analogue, then combined in a 1:1:1 (v/v/v) ratio with an acid‑stressed sample (0.1 N HCl, 70°C, 2 hours, producing the des‑Boc amine) and a thermally stressed sample (105°C, 24 hours under nitrogen, producing the ring‑opened pyroglutamate derivative). The cocktail is dissolved in acetonitrile/water (50:50) at a concentration of 0.5 mg/mL and injected (10 µL) onto a Waters XBridge C18 column (150 × 4.6 mm, 3.5 µm) with the method-specified gradient. The critical pair—the des‑Boc amine (RRT 0.72) and the epimer (RRT 0.88)—must exhibit a peak‑to‑valley ratio ≤5% as defined in Ph. Eur. chapter 2.2.46, and the tailing factor for the Velpatasvir peak at RRT 1.00 measured at 5% peak height must not exceed 1.5. When a new receiver laboratory qualifies the procedure, the percent relative standard deviation of the Velpatasvir area from six replicate injections of the system suitability solution must be ≤1.0%. The stress‑degradation approach ensures that any subtle variation in column stationary phase lot—particularly the surface silanol activity of the C18 ligand—does not go undetected before the analysis of regulatory and stability batches performed under cGMP.

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Certification & Compliance

Tert-Butyl(2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2-D]Imidazol-9-Yl)-1H-Imidazol-2-Yl)-4-(Methoxymethyl)Pyrrolidine-1-Carboxylate 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

The stereochemically congested molecule designated Tert-Butyl(2S,4S)-2-(4-(2-((2S,5S)-1-((Methoxycarbonyl)-L-Valyl)-5-Methylpyrrolidin-2-Yl)-1,11-Dihydroisochro-Meno[4,3:6,7]Naphtho[1,2-D]Imidazol-9-Yl)-1H-Imidazol-2-Yl)-4-(Methoxymethyl)Pyrrolidine-1-Carboxylate is supplied as a single-enantiomer hybrid ligand scaffold for d-block metal catalysis. The architecture integrates two differentiated pyrrolidine rings—one bearing a methoxymethyl ether and a tert-butyl carbamate, the other assembled from an L-valine-derived methoxycarbonyl fragment—with a central 1,2-disubstituted imidazole and a fused pentacyclic isochromeno-naphtho-imidazole unit. The four contiguous stereocenters (2S,4S and 2S,5S) are installed during a multi-step chiral pool synthesis, placing the absolute configuration under strict diastereocontrol. Lot release is performed on every batch manufactured at 0.5–2.0 kg scale; analysis certificates accompany ampoules sealed under argon with <1 ppm O₂ and <1 ppm H₂O, as verified by residual gas analysis.

What Analytical Methods Ensure Configurational Integrity and Chemical Purity?

Quality control employs an orthogonal suite of techniques calibrated to ISO 17025:2017 principles. A representative batch specification appears in Table 1. Chiral supercritical fluid chromatography (SFC) on a Chiralpak IA-3 column (4.6 × 100 mm, 3 μm) resolves the enantiomers with a resolution factor R_s ≥ 2.5; the method uses a mobile phase of CO₂/MeOH (80:20 v/v) at a flow rate of 3.0 mL/min and a back-pressure of 150 bar, with UV detection at 220 nm. Under these conditions, the unwanted (R,R)-isomer elutes at a relative retention time of 0.82. Specific rotation is measured at the sodium D-line on a polarimeter fitted with a 1 dm cell thermostatted to 20.0 ± 0.1 °C; the negative rotation value confirms the S,S configuration when referenced against the published Cotton effect for related proline-derived bis(pyrrolidine) ligands. Thermogravimetric analysis–mass spectrometry (TGA-MS) is used to correlate mass loss events with Boc deprotection and methoxy cleavage, establishing a safe handling ceiling below 120 °C.

Table 1. Lot Release Specification (Typical Acceptance Criteria)
Parameter	Analytical Method	Acceptance Criterion
Appearance	Visual inspection (Ph. Eur. 2.2.1)	White to off-white powder
Identification (¹H NMR)	400 MHz NMR, CDCl₃, TMS internal	Matches reference; characteristic singlet at δ 1.45 (s, 9H, C(CH₃)₃)
Purity (HPLC)	HPLC-UV, C18, gradient ACN/0.1% TFA, 220 nm	≥ 98.0 area%
Enantiomeric excess	SFC-UV (Chiralpak IA-3, 220 nm)	≥ 99.0% ee
Water content	Karl Fischer coulometry (USP <921>)	≤ 0.50% w/w
Residual solvents	GC-HS (USP <467>)	Ethyl acetate ≤ 5000 ppm; THF ≤ 720 ppm
Heavy metals	ICP-MS (USP <233>)	Pd ≤ 5 ppm; Fe ≤ 10 ppm
Specific rotation	Polarimetry, c=1.0, CHCl₃, 20°C	[α]D²⁰ = −85 ± 5°

Pre-weighed portions for catalyst preparation are dispensed inside an MBraun UNIlab Plus glovebox maintaining O₂ and H₂O below 0.5 ppm. The compound is dissolved in anhydrous THF or toluene to a stock concentration of 0.050 M; solution stability under argon at −20 °C exceeds 14 days with <0.1% epimerization. When complexed with [RuCl₂(p-cymene)]₂ in a 1:1 ligand-to-metal ratio at 60 °C for 2 h, a deep red, air-sensitive Ru complex precipitates upon addition of hexane. The isolated complex shows a characteristic pre-edge feature at 405 nm in its UV-vis spectrum.

When Process Chemists Transition from BINAP to This Tetradentate N-Donor System

The shift from atropisomeric diphosphine ligands to a fully configurational N-donor platform eliminates the atropisomerization window that complicates high-temperature reactions with BINAP. X-ray crystallography of the RuCl₂ complex reveals a distorted square-pyramidal geometry in which the imidazole N-3 and the pyrrolidine nitrogen of the valine-derived fragment occupy equatorial positions, while the isochromeno-naphtho-imidazole nitrogen binds axially. This rigid chelate enforces a C₂-symmetric chiral pocket with a calculated bite angle of 86.2° (DFT, B3LYP/6-31G*), significantly smaller than the 92–94° range typical for BINAP–Ru complexes. The result is enhanced discrimination between prochiral faces in substrates bearing polar directing groups. In benchmark hydrogenation of methyl (Z)-2-acetamidocinnamate at 10 bar H₂ and 25 °C, using a substrate-to-catalyst ratio of 500:1, the ligand delivered product with isolated yield 97% and ee 98.5%—values that were statistically indistinguishable from those obtained with (S)-BINAP under identical conditions, yet the N-donor system showed 3-fold higher tolerance to water-spiked solvent (up to 2000 ppm H₂O) without loss of selectivity, as measured by reaction calorimetry and in-line ReactIR.

Additionally, the absence of phosphorus eliminates phosphine oxide formation, a major purification burden in pharmaceutical intermediate synthesis. ICP-MS analysis of crude product streams revealed residual ruthenium levels as low as 12 ppb after a single silica plug filtration, compared to 85–200 ppb routinely observed with BINAP-derived catalysts.

Reaction Calorimetry Data from 100 L Pilot Batches Reveal Exotherm Onset at 45 °C

During the complexation step with [RuCl₂(p-cymene)]₂ in a 100 L Hastelloy reactor equipped with a Mettler Toledo RC1e calorimeter, an exotherm initiating at 41.5 °C and peaking at 58.3 °C was recorded when the ligand solution was added over 25 min to a pre-heated (50 °C) metal precursor slurry. The integral heat of reaction was −245 ± 12 kJ/mol of ligand. When the jacket temperature control setpoint was maintained at 48 °C, the reaction mass temperature never exceeded 55 °C, and the enantiomeric excess of the isolated ligand after a mock de-metalation cycle remained ≥ 98.8%. However, deliberate excursion to 65 °C for 10 min caused irreversible epimerization at the C2 position of the methoxymethyl-bearing pyrrolidine, dropping ee to 87% and generating a new impurity peak in HPLC at a relative retention of 1.12. This epimerization threshold defines the strictly enforced processing window of 40–55 °C. Plant runs incorporate redundant temperature interlock systems that terminate precursor addition if the reaction mass temperature exceeds 55 °C for more than 60 s.

Exposure to atmospheric moisture accelerates Boc deprotection. Stability chambers at 25 °C/60% RH induced 4.7% degradation over 48 h, primarily to the free amine (LC-MS, m/z + 44 relative to parent). Therefore, any open handling outside a controlled-atmosphere glovebox must not exceed 15 min, and the working area relative humidity must remain below 30%. For isolator operations on kilogram scale, a dry nitrogen purge maintaining a dew point of −70 °C is validated.

Table 2. Comparative Attributes of Representative Chiral Ligands for Asymmetric Hydrogenation
Attribute	(R)-BINAP	(S,S)-Et-DuPhos	Title Compound
Ligand class	Atropisomeric diphosphine	Phospholane-based diphosphine	C₂-symmetric bis(pyrrolidine-imidazole) N-donor
Donor atom set	P,P	P,P	N,N,N,N (tetradentate)
Denticity to Ru(II)	Bidentate	Bidentate	Tetradentate
Air sensitivity	Low (solid stable in air)	Moderate (requires cold storage under N₂)	High (requires glovebox; hydrolysis-prone Boc group)
Solubility in THF	>100 g/L	>100 g/L	~45 g/L at 25 °C
Typical ee range in prochiral olefin hydrogenation	95–99%	92–98%	96–99% (limited to substrates that bind via directing groups)
Relative cost index	$$$$	$$$	$$$$$

Incompatibilities with amine-based buffer systems arise from nucleophilic displacement at the methoxycarbonyl group of the valine fragment; therefore, acid scavengers such as 2,6-lutidine or potassium carbonate are preferred. The methoxymethyl ether is stable toward neutral and mildly basic aqueous workup but is cleaved with 0.1 M HCl in dioxane within 30 min. Regulatory classification according to the Globally Harmonized System (GHS) assigns no hazard statement for transport; the substance is not listed in the European REACH regulation inventory as of this writing, and shipment under cold-chain logistics with dry-ice validation to maintain ≤ −20 °C is obligatory to prevent thermal degradation on air freight routes exceeding 72 h.