4-Aminoisoxazole (CAS 108511-97-3, also 1,2-oxazol-4-amine or isoxazol-4-amine) is the simplest aminated isoxazole: a five-membered ring bearing a primary amine at the 4-position, with the molecular formula C₃H₄N₂O and a molecular weight of only 84.08 g/mol. That small size is the molecule’s commercial argument. Unlike heavily substituted heterocyclic building blocks, 4-aminoisoxazole introduces an isoxazole ring into a target molecule with minimal steric footprint, while the 4-amino group provides a reactive handle for acylation, sulfonylation, reductive amination and amide-bond formation. In medicinal chemistry, this combination has made the compound a recurring reactant in two specific and high-value discovery areas: the design of hydroxyethylene-based HIV-1 protease inhibitors containing a heterocyclic P1–P2 amide-bond isostere, and the synthesis of pyrimidine derivatives that act as selective Janus kinase 3 (JAK3) inhibitors. The market for 4-aminoisoxazole is not a tonnage market. It is a research-to-pilot specialty chemical supplied at ≥95% purity in milligram-to-gram packages, with catalogue pricing that reflects its research-scale status: 100 mg to 250 mg quantities from Japanese and international suppliers are priced in the tens of thousands of yen, and 1 g quantities exceed ¥100,000 at reference-grade suppliers. A note on CAS numbers is necessary here: the CAS number 36216-80-5, sometimes associated with “4-aminoisoxazole” in informal searches, actually corresponds to 1,2-benzisoxazol-3-amine, a fused benzisoxazole used in antipsychotic synthesis. The correct CAS for 4-aminoisoxazole is 108511-97-3, and its hydrochloride salt is 108511-98-4. For buyers, the qualifying question is therefore not simply “what does a gram cost” but “which supplier can deliver the correct molecule, at the specified purity, with analytical data that confirms the 4-amino substitution pattern rather than a positional isomer.”
Core Application Fields and Demand Architecture
Demand for 4-aminoisoxazole concentrates in three functional arenas where the 4-amino substitution on an unsubstituted isoxazole ring provides a combination of reactivity and steric economy that alternative building blocks cannot replicate: JAK3 inhibitor discovery, HIV-1 protease inhibitor design, and custom synthesis for medicinal chemistry programs.
In JAK3 inhibitor discovery, 4-aminoisoxazole serves as a reactant in the synthesis of pyrimidine derivatives that act as selective Janus kinase 3 inhibitors. JAK3 is a protein tyrosine kinase involved in cytokine and growth-factor signalling, and selective JAK3 inhibition is a pursued strategy in autoimmune and inflammatory disease research. The 4-amino group of the isoxazole can be incorporated into the kinase inhibitor scaffold through amide or amine linkages, while the isoxazole ring contributes hydrogen-bonding geometry and metabolic stability. The commercial significance of this application is tied to the intensity of JAK3 medicinal chemistry programs rather than to any single clinical candidate, and demand is therefore project-driven and fragmented across research groups.
In HIV-1 protease inhibitor design, 4-aminoisoxazole is used in the synthesis of hydroxyethylene-based inhibitors containing a heterocyclic P1–P2 amide-bond isostere. Protease inhibitors rely on transition-state mimetics to block viral maturation, and the P1–P2 amide-bond isostere is a critical structural element that determines binding affinity and metabolic stability. The isoxazole ring can serve as a compact, metabolically robust isostere component, and the 4-amino group provides a point of attachment for further elaboration. This segment is smaller than JAK3 discovery in current volume, but it is strategically durable because HIV protease inhibitor research continues to seek new scaffolds against resistant viral strains.
Custom synthesis and medicinal chemistry programs form the third arena. 4-Aminoisoxazole is catalogued as a heterocyclic building block and a key intermediate for pharmaceutical and agrochemical synthesis, and suppliers offer it both as a catalogue item and as a custom-synthesis starting point. A program that begins with a 100 mg qualification lot may later require gram quantities under a locked specification, and the supplier’s ability to follow that transition without changing the analytical method or impurity profile is part of the product’s value.
Regulatory Profile: A Research-Scale Heterocycle with an Irritant Classification and Inventory-Listing Sensitivity
4-Aminoisoxazole is not a CMR substance and is not on the SVHC Candidate List. Its regulatory identity is defined by a handling-hazard classification, by inventory-listing status in key markets, and by the analytical specifications that determine whether the material is the correct positional isomer.
The hazard profile is that of a solid irritant. GHS classification for 4-aminoisoxazole is GHS07 (Warning), consistent with the irritant profile typical of heterocyclic amines. For the hydrochloride salt, the classification is similarly irritant in nature. These are handling hazards—skin, eye and respiratory irritation—rather than carcinogenicity, mutagenicity or reproductive toxicity classifications, and the required precautions are standard for a fine-chemical solid: avoid dust generation, wear protective gloves and eye protection, and use in a well-ventilated area.
Inventory status is a qualification checkpoint. 4-Aminoisoxazole is a research-scale specialty chemical, and its listing status on inventories such as TSCA and REACH registries depends on the specific supplier and the volume placed on the market. Buyers in the United States and the European Union should confirm that the supplier’s inventory position supports the intended use, particularly if the material is intended for process development rather than laboratory research. For Russian and EAEU buyers, the compound is imported at research and pilot scale, and the practical documentation expectations are a Certificate of Analysis reporting identity and purity, a Russian-language SDS, and confirmation that the material is the 4-amino isomer rather than the 5-amino or 3-amino positional isomer.
The analytical specification is where the regulatory and quality dimensions converge. 4-Aminoisoxazole is commonly supplied at ≥95% purity, and the positional isomer—5-aminoisoxazole—has different biological activities and different reactivity. A lot that contains a significant proportion of the 5-amino isomer will behave differently in coupling reactions and may introduce an impurity that is difficult to purge. Suppliers that report lot-specific HPLC and NMR data, and that confirm the 4-amino substitution pattern, give the medicinal chemist a defensible basis for use.
Global Supply Structure and Manufacturer Differentiation
Global supply of 4-aminoisoxazole is fragmented and research-oriented. The supplier landscape includes catalogue and research-chemical companies such as Fluorochem, BenchChem, AKSci, Aladdin, Capot and a cohort of specialty producers, alongside custom-synthesis houses serving medicinal chemistry programs. There is no single dominant manufacturer exercising capacity control, and availability is measured in milligrams to grams rather than in kilograms. Purity specifications are typically ≥95%, with some suppliers offering 97% or 98% material, and package sizes range from 50 mg to 5 g or larger on custom order.
Differentiation operates on three axes. The first is isomeric purity and analytical depth. Suppliers that provide lot-specific NMR and HPLC data, and that explicitly confirm the 4-amino substitution pattern, reduce the risk of a positional-isomer impurity that could compromise a coupling reaction or a biological assay. The second axis is scale-up and custom-synthesis capability. A supplier that can follow a program from a 100 mg catalogue purchase to gram or tens-of-gram custom quantities, with a locked specification and consistent impurity profile, is more valuable than a catalogue vendor that cannot support the later stage. The third axis is documentation and language support. For Russian and EAEU buyers, a Russian-language SDS and a Certificate of Analysis that reports the lot-specific purity are baseline expectations, because the material is imported and the buyer’s incoming QC must be able to qualify it without re-characterizing every lot.
Regional Demand Dynamics
Demand for 4-aminoisoxazole follows the geography of medicinal chemistry and biotech R&D rather than the geography of chemical manufacturing.
North America and Europe are the principal demand centres, reflecting the concentration of JAK3 inhibitor discovery, HIV protease inhibitor research and contract research organizations in these regions. Demand is project-driven and small in absolute mass: a single medicinal chemistry group may purchase 100 mg to a few grams at a time, and a program that advances may require tens of grams. Buyers in these regions place weight on lot-specific analytical data and on the supplier’s ability to confirm the correct positional isomer.
Asia-Pacific, and China in particular, is the manufacturing and stock-holding hub for 4-aminoisoxazole. Chinese suppliers offer the compound as a catalogue item and as a custom-synthesis starting point, and the region’s demand is growing as domestic drug-discovery research expands. For Russian and EAEU buyers, China is the most accessible source of supply, and the practical qualification task centres on verifying the Certificate of Analysis and confirming the 4-amino substitution pattern.
Russia and the EAEU form a small, import-dependent contour. Demand comes from pharmaceutical R&D and medicinal chemistry groups, and supply is sourced from Chinese and international catalogue vendors. There is no meaningful domestic production of 4-aminoisoxazole, and the practical constraint is availability at the required purity and package size rather than regulatory restriction.
Future Outlook and Strategic Imperatives
The commercial trajectory of 4-aminoisoxazole is tied to the therapeutic areas it enables rather than to its own market size. JAK3 inhibitor discovery remains an active area of immunology and inflammation research, and the isoxazole scaffold continues to appear in medicinal chemistry patent literature and preclinical programs. HIV protease inhibitor research provides a second demand stream that is connected to the search for new scaffolds against resistant viral strains. Custom synthesis adds a service layer that grows with every program that chooses the 4-aminoisoxazole building block.
Three structural forces will shape the supply landscape. First, analytical transparency and isomeric confirmation will remain the primary differentiators. As programs mature, the building block’s purity and positional-isomer profile directly affect the purity of the final inhibitor, and buyers will increasingly require lot-specific NMR and HPLC data rather than a nominal 95% figure. Second, the transition from catalogue to custom scale will separate suppliers that can support a program’s growth from those that can only fill a small-pack order. Third, documentation and language support will matter more in import-dependent markets such as Russia and the EAEU, where the buyer’s incoming QC carries the qualification burden.
For Russian and EAEU buyers, the strategic implication is that 4-aminoisoxazole procurement should be treated as a specification-and-documentation decision rather than a price comparison. A lot that contains the 5-amino positional isomer, or a shipment that arrives without a Russian-language SDS and lot-specific analytical data, can cost more in lost synthesis time than the price difference between two suppliers. The lowest-risk source is the one that can confirm the 4-amino substitution pattern, provide lot-specific HPLC and NMR data, and support the program as it scales.
Shanghai XinChem Co., Ltd. (XinChem)
As a world-leading supplier of organic chemicals, Shanghai XinChem Co., Ltd. (XinChem) offers 4-aminoisoxazole (CAS 108511-97-3) in research-grade and custom-synthesis specifications, serving medicinal chemistry groups, JAK3 inhibitor discovery programs, HIV protease inhibitor researchers and pharmaceutical process development organizations. Our material is supplied with lot-specific analytical data, confirmed 4-amino substitution and the documentation support that heterocyclic building-block qualification requires at both catalogue and scale-up stages.
Technical and Quality Advantages
Lot-Specific HPLC and NMR Data: 4-Aminoisoxazole is supplied with a Certificate of Analysis reporting identity and purity by HPLC and NMR for the specific lot, rather than a generic catalogue specification. For JAK3 and HIV protease programs, where the building block’s impurity profile affects downstream coupling and biological activity, lot-level data allows the buyer to qualify the material against the program’s actual requirements.
Positional-Isomer Confirmation: The material is controlled for the 4-amino substitution pattern, with analytical data that distinguishes it from the 5-amino and 3-amino isomers. This specification is more informative than a headline HPLC percentage, because a positional isomer can behave differently in coupling reactions and introduce a downstream impurity that is difficult to purge.
Purity at the ≥95% Threshold with Scale-Up Continuity: Material is available at ≥95% purity (HPLC), consistent with the research-grade specification used across the specialty supplier market, and can be supplied in custom-synthesis quantities under a locked specification. A program that begins with a 100 mg qualification lot can later scale without changing the analytical method or the impurity profile.
Regulatory and Documentation Support: Safety data sheets are available in English and Russian, with documentation covering the GHS07 irritant classification and the inventory-listing position relevant to the destination market. For EAEU buyers, the Russian-language SDS and Certificate of Analysis support incoming qualification.
Packaging and Logistics Flexibility
4-Aminoisoxazole is available in sealed 100 mg, 250 mg, 1 g and 5 g containers for research and medicinal chemistry use, and in larger package sizes for custom-synthesis and process-development quantities. For Russia and EAEU destinations, XinChem arranges logistics with appropriate customs and transport documentation, including Russian-language SDS and Certificate-of-Analysis support, to reduce clearance friction for a building block that is sourced internationally at research scale.
Application Support and Supply Reliability
XinChem’s technical team assists with grade selection for JAK3 inhibitor and HIV protease inhibitor discovery, with coupling and amide-formation strategy for the 4-amino handle, and with the analytical and documentation requirements that heterocyclic building-block qualification demands. Supply schedules accommodate both catalogue-scale qualification orders and custom-synthesis volumes, with stock held for the package sizes most commonly requested in medicinal chemistry programs.
Why Choose XinChem
Expertise: Deep experience in heterocyclic amines and medicinal chemistry building blocks, with application knowledge spanning JAK3 inhibitor discovery, HIV protease inhibitor research and custom synthesis.
Consistency: Lot-specific control of identity, HPLC purity and positional-isomer composition—the parameters that determine whether 4-aminoisoxazole incorporates cleanly into a target inhibitor or introduces a purification burden.
Compliance Readiness: Documentation structured around the GHS07 irritant classification, inventory-listing positions and EAEU documentation expectations, with Russian-language SDS support.
Responsiveness: Direct technical and commercial access, with order structures from 100 mg qualification quantities to custom-synthesis volumes.
Contact us now to discuss your 4-aminoisoxazole requirements and request a specification sheet or qualification sample.
Website: www.xinchem.com
Email: sales1@xinchem.com
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Post time: Nov-01-2026