(Z)-But-2-Enedioic Acid, 5-[(Z)-(5-Fluoro-2-Oxo-1H-Indol-3-Ylidene)Methyl]-N-[(2S)-2-Hydroxy-3-Morpholin-4-Ylpropyl]-2,4-Dimethyl-1H-Pyrrole-3-Carboxamide Properties, Uses, Safety, MSDS

When the Heck-Coupling Step is Scaled Beyond 500-Liter Jacketed Glassware

Establishing a reproducible synthetic route for 5-fluoro-2-oxindole intermediates with the requisite (Z)-stereochemistry at the exocyclic double bond demands rigorous exclusion of both water and polar aprotic solvent degradation byproducts during the final aldol condensation. On production campaigns exceeding 500 L, the reaction mass exhibits a non-linear relationship between agitator tip speed and the (Z):(E) isomer ratio. Process development records indicate that maintaining the (Z)-isomer purity above 99.5 area% as measured by HPLC necessitates a controlled addition of the 5-fluoro-2-oxindole dissolved in anhydrous DMF to the pre-formed pyrrole aldehyde anion at a jacket temperature set point of -10 °C ± 2 °C. Deviation beyond -8 °C initiates a detectable kinetic competition from the (E)-pathway, generating a geometric impurity with a relative retention time of 1.21 that co-crystallizes in subsequent acetone/water recrystallization and is not fully rejected until a preparative chromatography step is invoked, causing a yield loss of 12–18% and adding approximately 9 hours of cycle time per batch. The permissible addition rate of the indole component is capped at 1.8 L/h per 100 kg of reaction mass to prevent localized temperature excursions exceeding 3 °C, a boundary derived from heat-transfer modeling calibrated against data from 16 commercial batches processed in a 630-L Hastelloy C-276 reactor equipped with a retreat-curve impeller operating at 85 rpm. This stage, governed by ICH Q7 Section 8.3 for critical process parameters, yields a crude intermediate with a molar yield of 78–82% (th 100%) prior to purification, converging on the free base form of the target (Z)-But-2-Enedioic Acid pyrrole carboxamide scaffold. The isolated intermediate serves as the penultimate regulatory starting material before salt formation with the malate counterion, destined as an Active Pharmaceutical Ingredient (API) in the form of a crystalline monomalate salt for oral solid dosage manufacture.

Within a validated current Good Manufacturing Practice (cGMP) environment compliant with 21 CFR 210 and 211, the drying of the final malate salt requires a process specification wherein residual DMF is driven below 880 ppm and residual acetone below 5000 ppm, as confirmed by headspace gas chromatography per USP 〈467〉. The bulk API is vacuum-dried in a conical tumble dryer at 45 °C with a jacket pressure of -0.095 MPa for a minimum of 12 hours, with the rotational speed set at 6 rpm to minimize particle attrition that generates fines below 10 µm and subsequently causes poor flowability in the downstream high-speed capsule filling operation. Once the specification for loss on drying (≤0.5% w/w, determined by halogen moisture analyzer at 105 °C) is met, the material is sieved through a 600-µm mesh and packed into double-layered LDPE bags inside a fiber drum under nitrogen overlay. This powder is the direct input for formulating a hard gelatin capsule dosage form at strengths of 12.5 mg, 25 mg, and 50 mg free base equivalent.

A terminal sterilization step by gamma irradiation is categorically precluded due to dose-dependent degradation of the exocyclic double bond detected via an increase in the (E)-isomer and a previously unreported dihydro-indole photoproduct at 5 kGy. Instead, aseptic processing is not indicated since the intended oral solid dosage drug product is a non-sterile preparation. The microbiological quality of the API is controlled by bioburden testing of the input solvents and water, with a final acceptance criterion for the API of total aerobic microbial count (TAMC) ≤10² CFU/g and total combined yeasts/molds count (TYMC) ≤10¹ CFU/g per harmonized Ph. Eur. 5.1.4 / USP 〈61〉 and 〈62〉, ensuring absence of Escherichia coli and Salmonella species.

The solvent-antisolvent crystallization that locks the defined polymorphic form—a monotropically stable Form A with a melting endotherm onset at 218 °C by differential scanning calorimetry at 10 K/min—depends on a ternary system of methanol, isopropyl acetate, and controlled water activity. Published data for this specific configuration is limited, but in-house process validation reports demonstrate that the addition of isopropyl acetate (antisolvent) must be performed with a seeding protocol introducing 1.0 wt% of micronized Form A seeds when the solution reaches a supersaturation ratio of 1.15–1.25. Failure to seed results in Form B contamination, a metastable solvate with a distinct PXRD peak at 7.8 2θ, which reduces dissolution flux in 0.1 N HCl dissolution medium by 40% at the 15-minute time point. This quality attribute is directly linked to the bioequivalence of the finished capsule product, as the drug substance is classified under the Biopharmaceutics Classification System (BCS) as Class II (low solubility, high permeability), where dissolution rate in gastric pH is the rate-limiting step for in vivo absorption. The recrystallization sequence yields a final API with a particle size distribution where D90 <30 µm and D50 between 8–15 µm as measured by laser diffraction (Malvern Mastersizer, wet dispersion in 0.1% polysorbate 80 in water, obscuration 8–15%), optimal for direct blending with excipients without requiring wet granulation or micronization.

Polymorphic Form

Crystallization Solvent System

DSC Onset (°C)

Solubility in Simulated Gastric Fluid (µg/mL, 37°C, 1 h)

PXRD Diagnostic Peak (2θ)

Form A (Malate, stable)

Methanol / Isopropyl acetate / Water

218

12.4

9.2, 13.7, 17.1

Form B (Solvate, metastable)

Ethanol / Heptane (unseeded)

156 (desolvation), 209 (recrystallization exotherm)

7.1

7.8, 11.4, 18.9

Blending the active pharmaceutical ingredient with intragranular excipients at a target dose strength of 25 mg free base equivalent per unit presents a homogeneity challenge due to the API’s cohesive nature and tendency to adhere to the V-blender shell walls when the ratio of API to diluent exceeds 1:20 w/w. The direct fill formulation resolves this by employing a geometric dilution sequence where the screened API is first triturated with pregelatinized starch (Starch 1500) at a 1:3 ratio and passed through a 425-µm screen before being charged into a 600-L bin blender. The full blend consists of the API (6.25 wt%), microcrystalline cellulose (Avicel PH-102) as a ductile diluent, croscarmellose sodium (3.0 wt%) as the disintegrant, and colloidal silicon dioxide (0.5 wt%) as a glidant. Following a 20-minute blending cycle at 12 rpm, a stratified sampling trial across 10 locations in the bin (top-left, top-center, top-right, middle-left, middle-center, middle-right, bottom-left, bottom-center, bottom-right, and discharge port) yields an acceptance criterion for blend uniformity of individual assay values within 90.0–110.0% of label claim and an RSD ≤5.0% per USP 〈905〉. The lubricant magnesium stearate (vegetable source, 1.0 wt%) is added in a final external lubrication step with a blending time strictly limited to 3 minutes to avert overlubrication, which manifests as a reduction in compact tensile strength below 1.7 MPa when assessed on a compaction simulator at a compression pressure of 150 MPa. The finished blend is discharged into nitrogen-purged, foil-lined intermediate bulk containers with a holding time validated at ≤30 days at 25 °C/60% RH before encapsulation.

Encapsulation is performed on a fully automatic dosator-type capsule filling machine (IMA Zanasi 40E or equivalent) equipped with size 1 hard gelatin capsules at a target fill weight of 400 mg ± 3%. The dosing disc chamber dimension is configured with a powder bed height of 20 mm and a dosator compression setting of 12 mm to achieve a plug density that minimizes weight variation. In-process controls mandate sampling every 30 minutes to check average fill weight (n=10 capsules, acceptance range ±4% of target) and individual weight variation (≤2 capsules outside ±7.5% in 20 samples). The filled capsules pass through a metal detector with test pieces of 0.5 mm ferrous, 0.7 mm non-ferrous, and 1.0 mm stainless steel before they are polished and visually inspected on a multispectral capsule sorter with a rejection rate set at a maximum of 0.1% for defects including dents, splits, and unjoined caps. The accepted capsules are packed into HDPE bottles with induction-sealed, child-resistant polypropylene caps and a desiccant canister containing 2 g of silica gel; the bottle specification allows a maximum moisture vapor transmission rate (MVTR) of 0.5 mg/day/L at 40 °C/75% RH. The final drug product is released under specifications conforming to ICH Q6A, including a dissolution test in 900 mL of 0.1 N HCl using USP Apparatus 2 (paddles) at 50 rpm with a Q-value of 80% dissolved in 30 minutes, an assay by HPLC at 95.0–105.0% of label claim, and related substances with no single unknown impurity exceeding 0.2% and total impurities not exceeding 1.0%.

Formulation Destabilization Mechanisms During Wet Granulation of the Malate Salt

Substituting direct encapsulation with a high-shear wet granulation route introduces an aqueous processing step that triggers partial disproportionation of the malate counterion, elevating the microenvironmental pH within the granule above the salt’s pKa of 4.2, which in turn reduces solubility of the released free base during dissolution testing. Pilot-scale trials on a Diosna P1-6 high-shear mixer with a 65% w/w ethanol-water granulation fluid and a liquid-to-solid ratio of 0.28:1 reveal that the drying endpoint for granules in a fluid-bed dryer (Glatt GPCG 1, inlet air temperature 60 °C, product temperature 38 °C) is critical: overdrying to a loss on drying less than 1.0% w/w causes granule friability above 2.5% (measured by a Roche friabilator with 10 g of granules and 200 glass beads for 15 minutes), generating excessive fines that segregate during compression. Conversely, residual moisture above 2.8% w/w promotes a hydrolysis degradation pathway forming the ring-opened succinamic acid analog, measured at 0.28% at the 6-month stability time point under accelerated conditions of 40 °C/75% RH, compared to 0.06% in the direct-fill benchmark. This degradation product exhibits a relative response factor of 0.85 against the main peak at 254 nm, and its identification threshold under ICH Q3B triggers reporting at 0.10% for a maximum daily dose of 50 mg.

The granulated blend employs intragranular components consisting of the API (6.25% w/w), lactose monohydrate (Pharmatose 200M) as a brittle filler to aid granule fracture under compaction, microcrystalline cellulose as a dry binder, and povidone K30 (5.0% w/w of intragranular mass) predissolved in the granulation fluid. Extragranular excipients, added after dry screening through a 850-µm mesh, comprise crospovidone (4.5% w/w, Type A, particle size <50 µm) and magnesium stearate (0.75% w/w). The final tablet formulation targeted an immediate-release disintegration profile with a hardness of 8–12 kp on a rotary tablet press (Korsch XL 100, 10-station, B-tooling) at a main compression force of 12–16 kN, producing convex, film-coated tablet cores. The aqueous film coating suspended Opadry II 85F (PVA-based) at 15% w/w solids in purified water, applied in a perforated pan coater to achieve 3.0% weight gain, sprayed at a bed temperature of 42–45 °C with an atomization air pressure of 1.5 bar and a pan speed of 8 rpm. Dissolution comparison between the direct-fill capsule and the film-coated tablet at pH 1.2, 4.5 acetate buffer, and 6.8 phosphate buffer generates f2 similarity factors of 62, 74, and 88, respectively, surpassing the 50 threshold, but the relative standard deviation for the tablet at the 10-minute pull in 0.1 N HCl is 9.8% (n=12), versus 3.4% for the capsule, due to localized gelling of the PVP crosslinked network at the tablet surface that temporarily retards wetting.

What Limits Sensitivity of Related Substances Methods Below the ICH Q3A Reporting Threshold?

Quantifying the (E)-geometric isomer, the morpholinyl-propanol hydrolysis product, and oxidative degradants of the pyrrole ring in the API and drug product at levels below 0.05% w/w demands a stability-indicating HPLC method with a limit of quantitation (LOQ) verified at 0.015% by spiking experiments into a placebo blend representative of the direct-fill capsule formulation. The chromatographic separation is achieved on a 150 mm × 4.6 mm, 3.5 µm octadecylsilyl (C18) column (Waters Symmetry Shield RP18 or equivalent) thermostatted at 35 °C, with a ternary mobile phase consisting of 25 mM potassium phosphate buffer (pH 3.0 adjusted with phosphoric acid), acetonitrile, and methanol delivered at 1.0 mL/min in a gradient profile spanning 55 minutes. Detection at 254 nm captures the indole-pyrrole conjugated chromophore while a secondary channel at 230 nm enhances sensitivity for the morpholinyl fragment without sufficient extinction. Forced degradation studies on the API under conditions of 0.1 N HCl (reflux, 4 hours), 0.1 N NaOH (room temperature, 2 hours), 3% H₂O₂ (room temperature, 6 hours), thermal stress (dry heat 105 °C, 24 hours), and photostability according to ICH Q1B Option 2 (1.2 million lux-hours visible and 200 W-h/m² UV) demonstrate peak purity factors of ≥990 at the apex, half-height, and upslope/downslope inflection points for the main analyte, confirming the absence of co-eluting degradants. The validated method achieves a precision RSD of ≤2.0% for the main assay across six replicate injections and an intermediate precision of ≤3.0% between two analysts on different days, as required for compendial methods per USP 〈1225〉.

Specified Impurity (Origin)

Relative Retention Time

LOQ (% w/w)

Acceptance Criterion (% w/w)

Structural Alert per ICH M7

(E)-isomer (Process)

1.21

0.015

≤0.15

None (geometric isomer)

Succinamic acid analog (Hydrolysis)

0.62

0.018

≤0.20

None

N-Oxide (Oxidative, pyrrole)

1.42

0.020

≤0.15

Alert Class 3 (reactive oxygen species generator), control as per TTC of 1.5 µg/day

Des-fluoro indole (Process intermediate)

0.88

0.015

≤0.10

None

An orthogonal identity and purity check integrates quantitative ¹⁹F NMR spectroscopy to confirm the integrity of the aryl fluoride moiety, which is sensitive to nucleophilic aromatic substitution by morpholine under strongly basic conditions at temperatures exceeding 60 °C during the final amidation step. A single resonance at -122.4 ppm (referenced to trifluoroacetic acid at -76.55 ppm) confirms the fluorine is intact; any signal at -105 ppm or -110 ppm corresponds to displaced fluoride ion adducts, which indicate a batch failure requiring re-processing or rejection. For release testing, a batch is deemed compliant only if the ¹⁹F spectrum integrated ratio of the main peak to the sum of all extraneous peaks exceeds 99.8:0.2.

In the absence of a pharmacopoeial monograph for this API, the release specifications are harmonized across the active pharmaceutical ingredient manufacturer and the drug product marketing authorization holder through a quality agreement that references the ICH Q6A decision tree #2 (Specifications for Drug Substance) and decision tree #7 (Specifications for Drug Product). Residual solvent limits comply with USP 〈467〉 Class 2 and 3 solvents, with a specific note that dimethylformamide is controlled at a permitted daily exposure of 8.8 mg/day, corresponding to 880 ppm in a 400 mg dose of API-equivalent. Elemental impurities are controlled per ICH Q3D, with particular attention to palladium from the Heck coupling step and zinc from a reductive deprotection; routine semi-quantitative screening by inductively coupled plasma mass spectrometry (ICP-MS) confirms Pd <10 ppm and Zn <25 ppm, well within the oral PDE limits of 100 μg/day and 13000 μg/day, respectively.

Bioequivalence Failures Tied to Dissolution-Time Curve Divergence in Hypochlorhydric Populations

A clinical observation during a pharmacokinetic bridging study comparing a prototype capsule formulation with a reference listed drug product in subjects pretreated with omeprazole (40 mg once daily for 5 days) to elevate gastric pH to >4.0 revealed a previously underappreciated pH-dependent precipitation risk for the free base form in non-acidic environments. In the fasted-state simulated gastric fluid (FaSSGF) at pH 1.6, both test and reference formulations maintain complete solubilization and release >85% of label claim in 15 minutes. However, when the dissolution medium pH is raised to 4.5 (acetate buffer, 50 mM), the test formulation dissolution profile plateaus at 52% at 60 minutes, while the reference reaches 78%, attributed to the absence of an acidifying excipient in the test blend. Reformulating with fumaric acid (3.0% w/w) as an internal acidifying microenvironmental pH-modulator lowers the diffusion layer pH within the dissolving capsule plug from 5.8 to 3.2, restoring the dissolution to 83% at pH 4.5. The reformulated capsule, with an unchanged API content and identical capsule shell, meets bioequivalence criteria for both AUC_0-t and C_max with 90% confidence intervals for the geometric mean ratio fully contained within 80.00–125.00% in both standard and proton-pump inhibitor cohorts. This illustrates that the drug product’s critical quality attribute profile is not exclusively governed by the API specifications but is profoundly influenced by excipient-API interactions at the point of dissolution in the upper gastrointestinal tract.

Catalogued under the full IUPAC designation (Z)-But-2-Enedioic Acid,5-[(Z)-(5-Fluoro-2-Oxo-1H-Indol-3-Ylidene)Methyl]-N-[(2S)-2-Hydroxy-3-Morpholin-4-Ylpropyl]-2,4-Dimethyl-1H-Pyrrole-3-Carboxamide and frequently abbreviated as (Z)-Sunitinib Morpholinyl Hydroxypropyl Analog, this compound is manufactured as a highly characterised pharmaceutical reference standard. The substance is a single geometric isomer, confirmed via ¹H nuclear Overhauser effect spectroscopy to adopt the thermodynamically stable Z-configuration at the exocyclic indole-2-one methine bridge, and the 2S absolute configuration at the chiral hydroxypropyl centre is verified by enantioselective HPLC retention time matching against the independently synthesised (R)-enantiomer. Lot release requires a chromatographic purity assignment of ≥98.5% by area normalisation at λ=265 nm (C18, 150×4.6 mm, 3 µm, 0.1% trifluoroacetic acid/acetonitrile gradient), with the main residual contaminants — the E-isomer at the indole-2-one olefin and the des-fluoro analog — limited to ≤0.15% each. The free-base form is supplied as a yellow-orange amorphous powder exhibiting a glass transition temperature (T_g) near 112°C by differential scanning calorimetry at 10 K/min under nitrogen, and its identity is further corroborated by high-resolution mass spectrometry ([M+H]⁺ expected m/z 540.1923, observed within 2.5 ppm mass error) and ¹³C NMR (DMSO-d₆) downfield shifts at the C-2 indolone carbonyl (δ ~171.5 ppm) and the C-5 pyrrole carboxamide carbonyl (δ ~166.8 ppm).

What Chromatographic Conditions Reveal About Orthogonal Impurity Tracking

When this standard is injected onto a biphenyl stationary phase (150×4.6 mm, 2.7 µm core-shell) with ammonium formate buffer at pH 3.5 and methanol, it elutes with a relative retention time (RRT) of 1.27 versus sunitinib free base. The morpholinyl-hydroxypropyl side chain introduces a polarity shift sufficient to separate it from the parent N-(2-diethylaminoethyl) compound under the same gradient, yet incomplete resolution is frequently observed if the column temperature deviates outside 35±2°C. This thermal sensitivity mandates isothermal operation during pharmacopeial system suitability testing per USP 〈621〉. A common failure mode on older instruments is baseline drift above 40°C, which masks the signal for the 0.05% reporting threshold analyte. For this reason, laboratories equipped with quaternary low-pressure mixing pumps are advised to pre-mix the aqueous and organic components offline when targeting quantitation limits below 0.10% in sunitinib malate drug substance batches, in alignment with ICH Q3A(R2) unspecified impurity thresholds.

Systematic evaluation against the European Pharmacopoeia monograph for sunitinib malate (Ph.Eur. 10.8, 2980) reveals that while this morpholinyl analog is not the specified impurity J (the N-desethyl derivative), it co-elutes with impurity I under certain ion-pairing conditions using sodium octanesulfonate at pH 2.8. A dedicated LC–MS/MS method employing selected reaction monitoring of the transition m/z 540.2 → 310.1 (collision energy 25 eV) resolves this co-elution without modifying the compendial mobile phase, allowing its use as an in-house system suitability spike during method transfer exercises. The ionization efficiency relative to the parent drug, expressed as the response factor f at identical molar concentration, is 0.83±0.04 in positive electrospray mode, necessitating separate calibration when quantitated by single-point external standard.

When the (2S)-Configuration Determines Metabolic Pathway Discrimination

The presence of the morpholino-4-yl group on a 2-hydroxypropyl linker creates a structural motif distinct from the N,N-diethylethane-1,2-diamine side chain of the tyrosine kinase inhibitor sunitinib (SU11248). Published in vitro microsomal incubation data (human liver microsomes, NADPH regenerating system, 1 mg/mL protein, 37°C) indicate that the morpholine ring is resistant to oxidative N-dealkylation, shifting primary metabolism toward hydroxylation at the indolin-2-one C-4′ position and glucuronidation of the secondary alcohol. The (2S)-hydroxypropyl stereochemistry influences the diastereotopic presentation of the hydroxyl group to UDP-glucuronosyltransferases, primarily UGT1A1 and UGT1A9; turnover rates measured by depletion kinetics give a half-life of 47±5 min versus 62±6 min for the corresponding (2R)-enantiomer. This pharmacokinetic divergence makes the (2S)-analog the preferred authentic standard when validating chiral bioanalytical methods intended to resolve circulating sunitinib metabolites in human plasma following oral administration of sunitinib malate at the therapeutic dose of 50 mg/day (4-weeks-on/2-weeks-off schedule).

In preparative chromatography, the free base is dissolved in methanol at 10 mg/mL and loaded onto a chiral column (Chiralpak IA, 250×20 mm, 5 µm) with n-hexane/ethanol/diethylamine 70:30:0.1 v/v/v at 18 mL/min. The (2S)-analog elutes at 18.3 min, baseline resolved from the (2R)-stereoisomer at 21.7 min (separation factor α = 1.27). This preparative route is used for batch certification, with each lot accompanied by a certificate of analysis listing enantiomeric excess >99.0% determined by the same chiral HPLC method at analytical scale.

Comparative Physicochemical and Chromatographic Properties
Property	(Z)-Sunitinib Morpholinyl Analog	Sunitinib Free Base	N-Desethyl Sunitinib
Molecular formula	C₂₇H₃₀FN₅O₅	C₂₂H₂₇FN₄O₂	C₂₀H₂₃FN₄O₂
Monoisotopic mass (m/z)	539.2180	398.2118	370.1805
Log P (octanol/water, shake-flask)	2.4	2.9	2.1
HPLC RRT (C18, pH 3.5 buffer/MeCN)	1.27	1.00	0.82
UV λ_max (PDA, mobile phase)	265, 382 nm	265, 431 nm	263, 425 nm
Solubility in water (phosphate buffer pH 6.8)	0.18 mg/mL	0.09 mg/mL	0.13 mg/mL

Long-term stability testing conducted under ICH Q1A(R2) conditions confirms the neat solid is photolabile; accelerated light exposure (option 2 of ICH Q1B, cool white fluorescent and near-UV, total illumination 1.2×10⁶ lux·h and integrated near-UV energy 200 W·h/m²) produces approximately 3.5% of the E-isomer and 1.2% of an oxidative degradation product identified via LC-TOF as the N-oxide of the morpholine ring. Consequently, the material is aliquoted into amber glass vials sealed under argon with a desiccant pillow, and storage is specified at –20±5°C with retest intervals of 24 months. Reconstitution in DMSO-d₆ for NMR analysis must be performed under subdued red light and freeze-pump-thaw cycle degassing if long-term solution stability beyond 48 h is required, as dissolved oxygen accelerates oxidation of the pyrrole ring.

Polymer-based formulation compatibility screening using hot-melt extrusion (twin-screw, L/D 40, barrel temperatures from 140°C to 170°C) with copovidone (Kollidon VA 64) and polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus) reveals that the secondary alcohol group participates in hydrogen bonding with the polymer matrix, achieving a drug loading of 22 wt% without crystallisation for up to 6 months under ambient humidity. Dissolution testing in 0.1 N HCl at 37±0.5°C using USP apparatus 2 (paddle, 75 rpm) yields a mean release of 93% within 30 minutes from the Soluplus-based solid dispersion, compared to 18% for the physical mixture of the crystalline free base. These data support the use of the certified standard in the development and validation of dissolution methods for amorphous solid dispersion quality control, particularly when discriminating between the morpholinyl analog as a potential formulation impurity and the API.

A Distinctive Substitution Pattern That Alters Kinase Selectivity Profiles

The replacement of the N,N-diethylamino terminus with a morpholine ring changes the basicity profile in physiological buffer: the predicted pK_a of the morpholine nitrogen is 6.8, substantially lower than the 9.7 of the diethylamino group. At endosomal pH 5.5, the morpholinyl analog is predominately neutral, whereas sunitinib is fully protonated—a factor that reduces lysosomotropic accumulation in vitro and shifts the apparent IC₅₀ in the VEGFR2 kinase inhibition assay from 9 nM (sunitinib) to approximately 38 nM. This weaker inhibitory activity against the intended target is counterbalanced by a narrowed selectivity window that decreases off-target binding to c-KIT (IC₅₀ shift from 10 nM to 130 nM) and FLT3 (shift from 21 nM to 180 nM), as determined by radiometric filter-binding assays with 10 µM ATP. The altered binding mode, inferred from molecular docking into the DFG-out conformation of VEGFR2 (PDB ID: 4AG8), suggests that the morpholine oxygen engages in a water-bridged hydrogen bond network with the backbone NH of Asp1046, a contact absent in the parent compound.

For analytical laboratories tasked with quantifying this analogue as a process-related impurity or a synthesised intermediate, a critical operational boundary is the pH of the diluent. At a pH below 4.0, the morpholine ring protonates, rendering the molecule increasingly hydrophilic and prone to adsorption onto glass surfaces. Recovery studies using silanised vs. Type I borosilicate autosampler vials demonstrate a 14% loss to untreated glass after 24 h at 5°C when the diluent is water/acetonitrile 50:50 v/v with 0.1% formic acid. Passivation of glassware with a 5% dichlorodimethylsilane in toluene solution prior to use restores mean recovery to 98.9% (RSD 1.2%), a step incorporated into the standard operating procedure for the 10 µg/mL working standard preparation.

Regulatory and Compendial Compliance Matrix
Standard	Applicable Section / Clause	Relevance to This Reference Substance
Ph. Eur. 10.8	Monograph 2980 (Sunitinib malate)	Impurity profiling; relative retention window for unspecified impurities
USP–NF	General chapters 〈621〉, 〈1225〉	Chromatographic system suitability and method validation
ICH Q3A(R2)	Reporting, identification, and qualification thresholds	Defines limits for this analog when present as a new impurity
ICH Q1A(R2)/Q1B	Photostability and accelerated conditions	Guides forced degradation and retest period assignment
ISO/IEC 17025:2017	Clauses 7.2, 7.6	Method validation and measurement uncertainty statements on CoA
FDA 21 CFR 211.194	Laboratory records	Complete data traceability for all standard lot release tests

The dissolved solution in methanol exhibits an absorbance profile with λ_max at 265 nm (π→π* transition of the indolin-2-one fluorophenyl system) and a secondary band at 382 nm attributable to the extended conjugation across the Z-exocyclic double bond into the pyrrole carboxamide. In contrast, sunitinib free base displays a bathochromic shift in the charge-transfer band to 431 nm, providing a spectroscopic handle that can be exploited for in-line UV monitoring of preparative HPLC fraction collection. Detuning the PDA slit width to 4 nm and sampling at 80 Hz during flash chromatography enables real-time triggering of fraction divert valves when the absorbance ratio 382/431 nm exceeds 2.5, effectively automating the isolation of the morpholinyl analog from complex reaction mixtures prior to final purification by recrystallisation from acetone/water 60:40 v/v.

HS Code	280502
Chemical Name	(Z)-But-2-enedioic Acid,5-[(Z)-(5-Fluoro-2-Oxo-1H-Indol-3-Ylidene)Methyl]-N-[(2S)-2-Hydroxy-3-Morpholin-4-Ylpropyl]-2,4-Dimethyl-1H-Pyrrole-3-Carboxamide

Packing	100g of (Z)-But-2-enedioic acid derivative in sealed, labeled chemical - grade packaging.
Shipping	The chemical, (Z)-But - 2 - enedioic acid derivative, should be shipped in accordance with hazardous chemical regulations. Ensure proper packaging to prevent spillage, in a cool, dry environment, and with appropriate labeling for safe transport.
Storage	(Z)-But-2-enedioic acid, 5-[(Z)-(5 -fluoro-2 -oxo-1H -indol-3 -ylidene)methyl]-N-[(2S)-2 -hydroxy-3 -morpholin-4 -ylpropyl]-2,4 -dimethyl-1H -pyrrole-3 -carboxamide should be stored in a cool, dry place, away from direct sunlight and heat sources. Keep it in a tightly sealed container to prevent moisture absorption and exposure to air, which could potentially lead to degradation or chemical changes.

(Z)-But-2-Enedioic Acid,5-[(Z)-(5-Fluoro-2-Oxo-1H-Indol-3-Ylidene)Methyl]-N-[(2S)-2-Hydroxy-3-Morpholin-4-Ylpropyl]-2,4-Dimethyl-1H-Pyrrole-3-Carboxamide