7-Chloroquinaldine (7-Chloro-2-methylquinoline, CAS 4965-33-7, C₁₀H₈ClN, MW 177.63 g/mol) is a quinoline heterocyclic building block and key pharmaceutical intermediate for antimalarial drug synthesis. The 7-chloro position is specifically critical for antimalarial activity through two mechanisms: (1) Ion trapping — the electron-withdrawing chlorine fine-tunes the quinoline pKa, optimizing the weak-base character that drives selective accumulation in the acidic digestive vacuole of Plasmodium falciparum (pH ~5.2). The neutral form passively diffuses across membranes; once protonated in the acidic vacuole, the charged drug is trapped and concentrated 100–1000x relative to plasma. (2) Heme binding — the chlorine substituent enhances pi-stacking interactions between the quinoline ring and ferriprotoporphyrin IX (FPIX, “free heme”) released during hemoglobin digestion. The drug-heme complex inhibits heme polymerase (heme detoxification protein, HDP), preventing the parasite from neutralizing the toxic heme. SAR studies show that removing or relocating the 7-chloro group reduces antimalarial potency by 10–100x — confirming its essential pharmacophoric role. The 2-methyl (quinaldine) group adds metabolic stability by blocking CYP450 oxidation at C2. UPOR Biotech supplies 7-chloroquinaldine at ≥99% GC (pharma intermediate grade) with full characterization data (COA, MSDS, GC chromatogram, 1H NMR, FTIR, stability data).

The quinoline scaffold in chloroquine analogs operates through a multi-step antimalarial mechanism that has made it one of the most successful drug classes in history. (1) Passive diffusion and ion trapping — the neutral, lipophilic form of the 4-aminoquinoline crosses the parasite plasma membrane, erythrocyte cytoplasm, parasitophorous vacuole membrane, and digestive vacuole membrane. Inside the acidic digestive vacuole (pH ~5.2), the weakly basic quinoline nitrogen (pKa ~8.1 for chloroquine, ~9.7 for the side-chain tertiary amine) becomes protonated. The charged form cannot cross back through the lipid membrane, achieving 100–1000x intralysosomal concentration vs plasma. (2) Heme binding and detoxification inhibition — P. falciparum digests up to 75% of host erythrocyte hemoglobin, releasing large quantities of ferriprotoporphyrin IX (FPIX, heme) that is toxic to the parasite. Normally, the parasite detoxifies heme by polymerizing it into inert hemozoin crystals via heme polymerase (HDP). Chloroquine binds FPIX with Kd ~10⁻⁷ M, forming a cytotoxic drug-heme complex that inhibits HDP. (3) Membrane disruption and oxidative stress — the accumulating FPIX-chloroquine complex intercalates into the vacuolar membrane, causing lipid peroxidation, loss of ion gradients, and oxidative parasite death. The 7-chloro group enhances both ion trapping (pKa modulation) and heme binding (pi-stacking), while the 4-amino side chain provides additional FPIX binding contacts and modulates drug accumulation. This scaffold has been validated in >200 FDA-approved drugs and continues to drive antimalarial discovery for artemisinin-resistant strains. UPOR Biotech’s 7-chloroquinaldine provides the core quinoline scaffold for new-generation chloroquine analog programs.

Quinoline intermediates including 7-chloroquinaldine are extensively used across multiple kinase inhibitor programs because the quinoline core is a privileged adenine bioisostere for the kinase ATP-binding pocket. Key programs include: (1) Type II kinase inhibitors (DFG-out conformation) — the flat quinoline ring occupies the adenine-binding hinge region via hydrogen bonding to the kinase backbone (typically Met or Cys hinge residue), while the 7-chloro substituent projects into the hydrophobic allosteric back pocket that is accessible only in the DFG-out (inactive) conformation. This Type II binding mode confers high selectivity for targets including B-Raf V600E (melanoma), VEGFR2/PDGFR (angiogenesis), and c-Kit (GIST). (2) 4-Anilinoquinoline EGFR inhibitors — 7-chloroquinaldine is a direct precursor for 4-anilinoquinoline scaffolds via nucleophilic aromatic substitution or Buchwald-Hartwig coupling at C4. These compounds target EGFR including T790M and C797S resistance mutants in NSCLC, and serve as second- and third-generation EGFR TKI leads. (3) Multitarget quinoline kinase inhibitors — the quinoline scaffold’s planarity and hydrogen-bonding versatility enable simultaneous engagement of multiple kinases (e.g., c-Met + VEGFR2 or ALK + ROS1), a strategy for overcoming acquired resistance in GIST, NSCLC, and melanoma. (4) Fluorescent kinase probes — the intrinsic quinoline fluorescence (ex ~350 nm, em ~430 nm, quantum yield 0.3–0.6) enables development of environment-sensitive turn-on probes for kinase activity assays, binding-site occupancy measurements, and HTS screening formats. UPOR Biotech provides 7-chloroquinaldine at ≥99% GC suitable for demanding kinase medicinal chemistry programs. Custom library synthesis and scaffold diversification at C4, C5, C6, and C8 available.

The 2-methyl (quinaldine) group provides a built-in metabolic stability upgrade through three synergistic mechanisms. (1) CYP450 oxidation blockade at C2 — the C2 position of quinoline is the primary site of cytochrome P450-mediated oxidation, particularly by CYP1A2 and CYP3A4. In unsubstituted quinoline, this pathway accounts for >60% of metabolic clearance, producing a 2-quinolone metabolite. The methyl group sterically blocks access of the CYP450 heme-iron-oxo species to the C2 C-H bond, dramatically reducing oxidative metabolism. (2) Prevention of reactive quinoline-imine formation — unsubstituted quinoline at C2 can undergo sequential CYP450 oxidation to form a quinoline-imine (quinolinium) reactive intermediate. This electrophilic species can covalently modify proteins (forming quinoline-protein adducts via Michael addition of Cys/Lys residues), which is mechanistically linked to idiosyncratic hepatotoxicity observed with some quinoline drugs. The 2-methyl group eliminates this bioactivation pathway entirely by blocking the initial C2 oxidation step. (3) Electronic modulation of quinoline pKa — the electron-donating methyl group at C2 slightly increases the quinoline nitrogen pKa (by ~0.3–0.5 pKa units), enhancing the ion-trapping efficiency in acidic compartments (parasite food vacuole, tumor lysosomes). This synergizes with the 7-chloro electron-withdrawing effect for optimal antimalarial pharmacology — balancing accumulation, target engagement, and clearance. Together, the 2-methyl + 7-chloro substitution pattern (quinaldine scaffold) represents an optimized pharmacophore that medicinal chemists use as a starting point for programs requiring both potency and drug-like PK properties. UPOR Biotech’s 7-chloroquinaldine provides this optimized scaffold as a single, well-characterized intermediate — no need to introduce the 2-methyl group separately in a multi-step synthesis.

Every shipment of 7-chloroquinaldine includes a complete documentation package: COA (GC purity ≥99.0% pharma intermediate or ≥98.0% research grade, full impurity profile with individual impurity identification — including 7-chloroquinoline, 2-methylquinoline, and 5-chloro regioisomer — and quantification, heavy metals ≤10 ppm with Pb ≤2 ppm / As ≤1 ppm / Hg ≤1 ppm / Cd ≤1 ppm / Pd ≤5 ppm / Ni ≤5 ppm, residual solvents per USP <467> / EP <5.4> / ICH Q3C, loss on drying, residue on ignition, melting point range), MSDS (GHS-compliant, 16-section format with hazard classification, safe handling, and emergency procedures), GC Chromatogram (signed and dated, with integration table showing retention times, peak areas, and area% for main peak and all impurities), 1H NMR Spectrum (300 or 400 MHz, CDCl₃, with peak assignments: 2-CH₃ singlet ~δ 2.72, aromatic protons δ 7.2–8.1), FTIR Spectrum (ATR, with principal band assignments: C=N ~1595 cm⁻¹, C-Cl ~750 cm⁻¹, aromatic C-H ~3050 cm⁻¹), BSE/TSE-Free Statement, Non-GMO Statement, Allergen Statement, HALAL Certificate, KOSHER Certificate, ISO 22000 + HACCP, ISO 9001:2015, FDA Facility Registration, Stability Data (25°C/60%RH real-time 24-month and 40°C/75%RH accelerated 6-month per ICH Q1A), and Complete Lot Traceability from raw material procurement through synthesis, purification, QC release, and packaging. Free sample (100 mg – 1 g) available for qualified B2B buyers for analytical evaluation and method development. MOQ: 100 g (research grade) / 1 kg (pharma intermediate grade). All documents provided in English. Custom synthesis and process R&D support available for quinoline scaffold diversification — including C4 amination/arylation, cross-coupling, C8 hydroxylation, and nitrogen-directed C-H activation strategies.