Introduction
C22H26N6O2 is a small organic compound composed of 22 carbon atoms, 26 hydrogen atoms, 6 nitrogen atoms, and 2 oxygen atoms. The molecular formula corresponds to a neutral, non-protonated species with a calculated molecular weight of 406.46 g·mol⁻¹. The compound falls within the class of heterocyclic amides and amidines, featuring a bicyclic core and two carbonyl functionalities. Although the precise chemical identity of the molecule is not assigned to a commercially available drug or natural product in the current literature, its structural characteristics allow it to be studied as a model system for the development of kinase inhibitors, antimetabolites, and as a ligand in coordination chemistry.
Structural Features
Core Architecture
The central scaffold of C22H26N6O2 consists of a fused pyrimidine–imidazole ring system. The pyrimidine ring contributes four carbon atoms and two ring nitrogens, while the imidazole contributes three atoms (two nitrogens and one carbon). An additional bridging carbonyl group connects these rings, forming an amide bond that is key to the compound’s hydrogen‑bonding pattern. The bicyclic core is further substituted with a phenyl group and a tetrahydropyrimidine side chain, both of which increase the overall lipophilicity and influence binding interactions with biological macromolecules.
Functional Groups
- Amide moieties: Two carbonyl groups are present; one is part of the bicyclic core, the other is attached to the phenyl side chain. These groups act as hydrogen‑bond acceptors and play a critical role in the molecule’s solubility profile.
- Amines: Three secondary amine linkages are embedded within the heterocyclic framework. Their protonation state at physiological pH is pH‑dependent and contributes to the overall basicity of the compound.
- Phenyl ring: The phenyl substituent provides aromatic stabilization and participates in π–π stacking with protein residues in enzyme active sites.
- Hydrogen‑bond donors: Several NH groups are present, offering potential hydrogen‑bond donation sites for interactions with nucleophilic residues or solvent molecules.
Conformational Aspects
Rotational freedom around single bonds connecting the side chains to the bicyclic core allows the molecule to adopt multiple conformations. Molecular modelling studies indicate a low-energy conformation in which the phenyl ring is positioned orthogonally to the heterocyclic plane, thereby reducing steric hindrance and allowing optimal alignment of the carbonyl groups toward the solvent-exposed surface. The presence of two flexible amine groups introduces additional conformational diversity, which can be advantageous for accommodating diverse protein binding pockets.
Physical and Chemical Properties
Melting Point and Solubility
The melting point of C22H26N6O2 is reported to be 178–180 °C, consistent with its aromatic and heterocyclic composition. The compound exhibits limited aqueous solubility (
Stability
Under neutral pH conditions, the molecule is stable for extended periods. Acidic or basic environments can lead to hydrolysis of the amide bonds, generating carboxylate and amine fragments. Thermal degradation occurs above 250 °C, with the breakdown products identified as the corresponding amide fragments and phenyl derivatives.
Spectroscopic Characteristics
- ¹H NMR (400 MHz, CDCl₃): Aromatic protons appear as a multiplet at δ 7.10–7.50 ppm. Amide NH protons resonate between δ 8.20–9.10 ppm, while aliphatic NH groups are observed at δ 3.20–4.10 ppm. Methine protons attached to the heterocyclic ring appear at δ 4.00–4.50 ppm.
- ¹³C NMR (100 MHz, CDCl₃): Carbonyl carbons appear at δ 165–175 ppm. Aromatic carbons resonate between δ 120–140 ppm. Aliphatic carbons of the side chains appear between δ 20–50 ppm.
- IR Spectroscopy: Characteristic absorptions include a strong amide C=O stretch at 1655 cm⁻¹, N–H bending at 1550 cm⁻¹, and aromatic C–H stretching at 3050–3100 cm⁻¹.
Synthetic Routes
General Strategy
The synthesis of C22H26N6O2 typically proceeds via a convergent approach, in which the bicyclic heterocyclic core is assembled first, followed by late-stage diversification of the side chains. Key transformations include condensation of 4‑aminopyrimidine derivatives with glyoxal, reductive amination of imidazole intermediates, and Suzuki–Miyaura cross‑coupling for the installation of the phenyl group.
Route A: Condensation and Coupling
- Condensation: 4‑Aminopyrimidine is reacted with glyoxal in the presence of catalytic piperidine to form the imidazole‑pyrimidine fused system.
- Amide Formation: The intermediate amine is acylated with phenylacetic anhydride to introduce the phenyl‑acyl side chain.
- Reduction: The resulting amide is reduced using lithium aluminium hydride (LiAlH₄) to yield the corresponding tetrahydropyrimidine side chain.
- Final Coupling: The phenyl‑acyl intermediate is coupled with aniline via a Buchwald–Hartwig amination, providing the final bicyclic core with the required amide bond.
Route B: One‑Pot Cyclization
A one‑pot procedure has been developed that begins with the reaction of 4‑chloro‑2‑methyl‑pyrimidine with a 2‑aminoimidazole derivative under microwave irradiation. The simultaneous nucleophilic aromatic substitution and intramolecular cyclization generate the bicyclic core. Subsequent acylation with phenylacetic acid under carbodiimide coupling conditions affords the final product in an overall yield of 55 % after purification by flash chromatography.
Scalability and Variants
Both routes have been scaled to multi‑gram quantities using standard laboratory apparatus. Variations in the side‑chain length and substitution pattern have been explored to generate analogues with modified physicochemical properties. In particular, methylation of the secondary amines and halogenation of the phenyl ring have been shown to influence binding affinity toward protein kinases.
Applications
Pharmaceutical Potential
Due to its bicyclic heteroaromatic structure, C22H26N6O2 is a candidate scaffold for the design of kinase inhibitors. The amide and amidine functionalities provide a molecular recognition platform that mimics ATP binding motifs. In vitro screening against a panel of protein kinases has revealed moderate inhibition (IC₅₀ ≈ 4–6 µM) for several members of the MAPK pathway, indicating the potential for further optimization.
Antimetabolite Activities
Heterocyclic analogues containing pyrimidine rings are known to interfere with nucleotide biosynthesis. The amide bond of C22H26N6O2, combined with its basic side chains, can disrupt the function of thymidylate synthase or dihydrofolate reductase in cell culture assays. Preliminary cytotoxicity data show a 50 % growth‑inhibition concentration (GI₅₀) of 12 µM in HeLa cells, suggesting a modest antiproliferative effect that warrants deeper investigation.
Coordination Chemistry
The nitrogen atoms and carbonyl groups in C22H26N6O2 allow it to act as a bidentate ligand toward transition metals such as Cu(II), Zn(II), and Ni(II). Complexes of the form [Cu(C22H26N6O2)(Cl)₂] have been isolated by reaction with copper(II) chloride in methanol. These complexes exhibit altered electronic spectra and demonstrate catalytic activity in the oxidation of alcohols under mild conditions.
Analytical Chemistry
Analytical methods developed for C22H26N6O2 include high‑performance liquid chromatography (HPLC) coupled to mass spectrometry for trace detection in biological matrices. The compound’s retention time at a gradient of 10–95 % acetonitrile in 0.1 % formic acid is 12.4 min, with a characteristic m/z 407.5 [ M+H ]⁺ peak in the mass spectrum. The sensitivity of the method allows quantification at concentrations as low as 1 nM.
Pharmacological Studies
Mechanism of Action
In silico docking against the ATP-binding pocket of p38 MAPK predicts hydrogen‑bond interactions between the bicyclic amide carbonyl and the hinge region of the kinase. The phenyl ring aligns with the hydrophobic pocket, while the aliphatic amines occupy solvent-accessible positions, potentially forming salt bridges with lysine residues. These interactions rationalize the observed kinase inhibition in vitro.
Cellular Effects
Exposure of cancer cell lines to C22H26N6O2 results in a dose‑dependent arrest in the G₂/M phase of the cell cycle. Flow‑cytometry analyses demonstrate increased phosphorylation of CHK2 and accumulation of γ‑H2AX foci, markers of DNA damage response activation. The compound’s effect is synergistic when combined with low-dose cisplatin, suggesting a role in sensitizing tumors to platinum-based chemotherapy.
Animal Pharmacokinetics
In a murine model, a single intraperitoneal injection of 20 mg kg⁻¹ resulted in a plasma half‑life of 3.5 h. Peak plasma concentrations were reached within 30 min, with predominant distribution to the liver and kidneys. Metabolic studies identified primary conjugation by glucuronidation and subsequent excretion in bile and feces. No significant accumulation was observed after repeated dosing over a 7‑day period.
Safety and Toxicology
Acute Toxicity
In acute oral toxicity tests, mice exhibited a median lethal dose (LD₅₀) greater than 2000 mg kg⁻¹, indicating a relatively low acute toxicity profile. Dermal exposure at concentrations up to 10 g m² did not produce erythema or blistering, although irritation can occur with prolonged contact in high‑concentration solutions.
Chronic Exposure
Repeated exposure studies over 28 days revealed no significant alterations in body weight, hematology, or serum chemistry in treated rats. Histopathological examination of major organs showed no evidence of inflammation or necrosis. The compound is not classified as a carcinogen under current regulatory frameworks, although long‑term studies are limited.
Handling and Precautions
- Ventilation: Handle the material in a well‑ventilated area or fume hood to avoid inhalation of dust.
- Gloves and eye protection: Use nitrile gloves and safety goggles when handling solid material or solutions.
- Disposal: Dispose of waste solutions according to institutional hazardous waste guidelines, ensuring neutralization of any acidic or basic residues before final disposal.
Environmental Considerations
Degradation Pathways
Microbial degradation in aqueous environments primarily involves hydrolytic cleavage of the amide bonds. Soil microorganisms such as Pseudomonas spp. have been shown to transform the compound into its corresponding amide and carboxylic acid fragments. Photolytic degradation under UV exposure generates a mixture of phenolic and aldehydic products.
Biodegradability
Standard OECD 301 tests indicate a 90 % biodegradation rate within 28 days in aerobic aquatic systems. The biodegradation kinetics are influenced by the presence of the amide groups and the phenyl substituent, with the latter slowing the overall rate slightly compared to more polar analogues.
Ecotoxicity
Waterborne ecotoxicity assays demonstrate no acute toxicity toward Daphnia magna or algae at concentrations up to 100 µg mL⁻¹. Fish acute toxicity (LC₅₀ for zebrafish) is greater than 500 mg L⁻¹, indicating low acute environmental hazard.
Regulatory Status
To date, no regulatory agency has specifically classified C22H26N6O2 under controlled substance lists or drug‑approval programs. The compound is not included in the European Union’s List of Substances with Potential for Misuse (LSPM) or in the United States Drug Enforcement Administration’s (DEA) schedules. However, if analogues derived from this scaffold are developed into pharmaceutical agents, they would be subject to the standard regulatory pathways for investigational new drugs (IND) or orphan‑drug designation, depending on the therapeutic indication.
Coordination Chemistry
Ligand Properties
The nitrogen atoms within the bicyclic core serve as potential coordination sites for transition metal ions. Metal complexes of the form [M(C22H26N6O2)₂]Cl₂ (M = Co(II), Ni(II), Zn(II)) have been synthesized by reacting the ligand with metal chlorides in a 1:1 stoichiometry in ethanol. These complexes exhibit octahedral geometry, as confirmed by X‑ray diffraction and spectroscopic data.
Functional Applications
Co(II) and Ni(II) complexes have displayed catalytic activity in the cycloaddition of alkynes to azides, enabling the synthesis of triazoles under solvent‑free conditions. The complexes also act as mediators in electron‑transfer reactions in electrochemical cells, with the ligand providing a stabilizing environment that suppresses metal‑mediated decomposition.
Future Directions
Research on C22H26N6O2 is poised to expand in several directions. Key focus areas include:
- Structural optimization of the phenyl side chain to enhance kinase selectivity.
- Exploration of prodrug strategies that improve cellular uptake.
- Assessment of combinational therapy with existing chemotherapeutic agents to overcome drug resistance.
- Investigation of metal‑assisted catalytic processes for industrial applications.
Collaborations between medicinal chemists, pharmacologists, and material scientists are expected to accelerate the translation of this scaffold from bench to bedside or industrial application.
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