Views: 0 Author: Site Editor Publish Time: 2026-03-18 Origin: Site
In the sophisticated landscape of 2026 pharmaceutical manufacturing, 5-Methyl-4-isoxazolecarboxylic acid (CAS 42831-50-5) has transitioned from a niche intermediate to a cornerstone of modern immunology. While historically recognized in pharmacopeias as "Leflunomide Impurity D," its role in the contemporary industry is far more proactive. It serves as the primary high-purity scaffold for the synthesis of Leflunomide and its active metabolite, Teriflunomide—two essential disease-modifying antirheumatic drugs (DMARDs) utilized in the treatment of rheumatoid arthritis and multiple sclerosis.
The global surge in autoimmune research has placed a premium on this specific isoxazole derivative. In 2026, the industry standard has moved beyond simple "technical grade" material. Manufacturers now require an "Ultra-Pure" grade to ensure that final APIs meet the microscopic 0.1% impurity thresholds mandated by 2026 global health authorities. At EASTFINE, we have optimized our production to meet these exact specifications, providing a bridge between raw chemical synthesis and life-saving pharmaceutical applications.
5-Methyl-4-isoxazolecarboxylic acid (C5H5NO3) is a white to pale-yellow crystalline solid. Its structural signature is the five-membered isoxazole ring, characterized by adjacent nitrogen and oxygen atoms. The carboxylic acid group at the 4-position and the methyl group at the 5-position create a specific electronic density that is vital for the biological lock-and-key mechanism in human DHODH (dihydroorotate dehydrogenase) inhibition.
Molecular Weight: 127.10 g/mol
Melting Point: 144°C – 149°C
pKa Value: 2.85± 0.25
Boiling Point: 289.5°C (at 760 mmHg)
The fundamental precursor for the production of Teriflunomide, used extensively for relapsing-remitting multiple sclerosis.
A versatile building block for the creation of novel COX-2 inhibitors and advanced anti-fibrotic drug candidates.
Used by global QC laboratories to validate the purity of immunosuppressant batches through high-resolution HPLC profiling.
Achieving the requisite purity for CAS 42831-50-5 requires a mastery of heterocyclic cyclization, specifically to avoid the persistent "Isomer Contamination" of the 3-methyl variant.
Traditional batch processing often resulted in fluctuating yields and a higher carbon footprint. In 2026, EASTFINE has fully transitioned to Microchannel Continuous Preparation Technology.
We initiate a controlled reaction of 2-ethoxymethylacetoacetate with hydroxylamine hydrochloride in a specialized micro-reactor.
By managing the residence time to within seconds and maintaining a highly specific pH gradient, we achieve a cyclization efficiency of over 96%.
This process virtually eliminates the 3-methyl-isoxazole-4-carboxylic acid impurity, delivering a "Pharma-Ready" intermediate that requires significantly less downstream purification.
As a substituted organic acid with biological activity precursors, CAS 42831-50-5 must be handled with rigorous industrial hygiene as per 2026 GHS Revision 11 mandates.
Classified as a Category 2 Skin Irritant and Category 2A Eye Irritant. Prolonged contact can lead to localized chemical burns.
While not acutely toxic by inhalation, the fine crystalline dust can cause respiratory tract irritation (STOT SE 3).
If exposed to high heat (>200°C), the molecule decomposes to release toxic nitrogen oxides (NOx) and carbon monoxide.
All weighing and charging must occur within a HEPA-filtered laminar flow hood or a closed-loop powder transfer system.
EASTFINE provides this product in a granulated crystalline form to minimize aerosolization.
Store in a cool, dry, and well-ventilated area. In 2026, we recommend 2°C – 8°C for long-term storage to preserve the integrity of the carboxylic acid group.
Nitrile or Butyl rubber gloves (minimum 0.11 mm thickness).
If working outside an enclosure, an N95 or P3 particulate respirator is mandatory.
Chemical safety goggles are the baseline; a face shield is required during large-scale solvent dissolutions.
| Property | EASTFINE 2026 Standard | GHS / Safety Requirement |
|---|---|---|
| Assay (HPLC) | ≥ 99.0% | N/A |
| Appearance | White Crystalline Powder | N/A |
| GHS Signal Word | WARNING | Mandatory Labeling |
| Flash Point | 140.3°C | Combustible Solid |
| Storage Class | 11 | Flammable/Combustible Solids |
| Incompatibility | Strong Oxidizing Agents | Separate Storage Required |
In the competitive chemical economy of 2026, your choice of supplier determines your operational efficiency. EASTFINE Precision Chemistry is a recognized leader in the pharmaceutical and agrochem intermediate sector.
Our 2026 continuous flow technology ensures that isomeric impurities are kept below 0.05%, drastically reducing your API refinement costs.
Our microchannel process reduces solvent waste by 35% compared to traditional methods, aligning with global 2026 ESG targets.
We provide a comprehensive "Molecular Passport" with every batch, including HPLC traces, 1H-NMR spectra, and heavy metal analysis.
With 30 years of export experience, we ensure that your 5-Methyl-4-isoxazolecarboxylic acid arrives in vacuum-sealed, moisture-proof packaging, ready for immediate use in your reactor.
CAS 42831-50-5 is an indispensable molecule in the modern fight against autoimmune disorders. By implementing the 2026 safety standards and sourcing from a technical pioneer like EASTFINE, you ensure that your pharmaceutical production is safe, compliant, and scientifically superior.
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