[1,2,4]Triazolo[4,3-a]pyridine-3-carboxylic acid 98% Purity Fused Heterocyclic Building Block Kinase Inhibitor and Drug Discovery Research Key Interme

Product Overview

[1,2,4]Triazolo[4,3-a]pyridine-3-carboxylic acid (CAS 5543-08-8) is a high‑purity fused heterocyclic building block featuring a triazole ring fused to a pyridine ring with a carboxylic acid functionality at the 3‑position. The molecular formula is C₇H₅N₃O₂ with a molecular weight of 163.13 g/mol. It has a topological polar surface area (TPSA) of 67.49 Ų, a calculated LogP of 0.43 indicating moderate hydrophilicity, and contains one hydrogen bond donor and four hydrogen bond acceptors. The compound appears as an off‑white to pale yellow crystalline powder with a melting point of 166‑167 °C. It is soluble in polar organic solvents such as dimethyl sulfoxide and dimethylformamide. Supplied at ≥98.0% purity as determined by HPLC, this research‑grade reagent is manufactured under strict quality control to ensure batch‑to‑batch consistency. It is intended exclusively for scientific research purposes and is not for human consumption or clinical use.

Synthetic Process

The synthesis of [1,2,4]triazolo[4,3-a]pyridine-3-carboxylic acid typically involves the construction of the fused triazolopyridine core via cyclocondensation of 2‑hydrazinylpyridine derivatives with appropriate carbonyl compounds. A representative synthetic route is described below:

• Step 1 – Preparation of Hydrazinylpyridine Intermediate: 2‑Hydrazinylpyridine is prepared through the reaction of 2‑halopyridine with hydrazine hydrate under reflux conditions.

• Step 2 – Cyclocondensation: The 2‑hydrazinylpyridine derivative undergoes cyclization with an appropriate dicarbonyl compound (such as ethyl glyoxylate or glyoxylic acid) to form the fused triazolo[4,3-a]pyridine ring system. Oxidative cyclization using hypervalent iodine reagents such as PhI(OAc)₂ can also be employed to facilitate the N–N bond formation.

• Step 3 – Hydrolysis: The ester intermediate (ethyl [1,2,4]triazolo[4,3-a]pyridine-3-carboxylate) is hydrolyzed to the corresponding carboxylic acid using lithium hydroxide (LiOH·H₂O) in aqueous conditions.

• Step 4 – Purification: The crude product is purified by recrystallization from ethanol or methanol, or by flash column chromatography on silica gel (eluting with ethyl acetate‑hexane or dichloromethane‑methanol mixtures) to achieve ≥98% purity.

• Quality Control: The final product is rigorously characterized by HPLC analysis (purity ≥98.0%), ¹H‑NMR, ¹³C‑NMR, and mass spectrometry to confirm structural identity and purity.

Mechanism of Action / Application Principles

As a synthetic building block, [1,2,4]triazolo[4,3-a]pyridine-3-carboxylic acid serves as a versatile precursor for:

• Kinase Inhibitor Synthesis: The triazolopyridine scaffold is a privileged structure in medicinal chemistry, serving as a bioisostere of purine bases. It enables potent binding to a variety of biological targets including kinases, with applications in oncology and inflammatory disease research. For example, triazolopyridine-based spleen tyrosine kinase (Syk) inhibitors have demonstrated significant efficacy in preclinical models of rheumatoid arthritis, showing dose‑dependent reduction in paw swelling and pro‑inflammatory cytokine levels.

• Drug Discovery Programs: The scaffold's ability to serve as a hydrogen bond acceptor and donor enables favorable interactions with biological targets. The carboxylic acid group allows for the introduction of diverse substituents through amidation and esterification, facilitating the rapid generation of compound libraries.

• Anticancer Research: Triazolopyridine derivatives have been explored as inhibitors of various kinases involved in cancer progression, including EGFR and ERK pathway targets, with some analogs demonstrating IC₅₀ values in the low micromolar range against cancer cell lines.

• Fragment‑Based Drug Discovery: The compact, rigid structure with a molecular weight of 163 g/mol makes this scaffold an excellent candidate for fragment‑based drug discovery campaigns targeting protein‑protein interactions and enzyme active sites..

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