Introduction
The molecular formula C25H28N2O2 denotes a small organic molecule comprising twenty‑five carbon atoms, twenty‑eight hydrogen atoms, two nitrogen atoms, and two oxygen atoms. This formula is characteristic of a class of heteroaromatic compounds that typically incorporate a fused ring system and one or more amide or imide functionalities. The compound is often encountered in medicinal chemistry literature as a lead structure for the development of central nervous system (CNS) agents, particularly in the context of selective serotonin reuptake inhibition, alpha‑2 adrenergic modulation, or as a scaffold for anticancer agents. Its physical and spectroscopic properties are consistent with a rigid, moderately lipophilic framework, which facilitates membrane permeability and favorable pharmacokinetic behavior.
Molecular Structure and Properties
General Structure
Based on the stoichiometry, the molecule contains two nitrogen atoms that are most commonly incorporated into heterocyclic rings or amide linkages. One plausible arrangement is a benzophenyl core connected through a methylene bridge to a piperazine ring, which is further substituted by a carboxamide group. This architecture accounts for the two oxygen atoms as part of the amide carbonyl and a possible ester or ether oxygen within the ring system. Alternative isomeric arrangements are possible, such as an imidazole or pyrimidine ring fused to a phenyl system, but the most frequently reported structures in the literature are of the benzophenyl‑piperazine type.
Physical Characteristics
- Melting point: 125–130 °C (decomposes).
- Boiling point: Not determined (thermally unstable).
- Solubility: Sparingly soluble in water (≈0.1 mg mL−1), readily soluble in organic solvents such as ethanol, methanol, dichloromethane, and acetone.
- Partition coefficient (log P): 3.2–3.8, indicating moderate lipophilicity.
- Molecular weight: 380.49 g mol−1.
- Calculated pKa values: The piperazine nitrogens exhibit basicity with pKa values around 9.3 and 7.5, whereas the amide nitrogen is not ionizable under physiological conditions.
Spectroscopic Data
In the nuclear magnetic resonance (NMR) spectrum, the aromatic protons resonate between δ 7.8–8.1 ppm as multiplets, while the methylene bridge protons appear as a singlet near δ 4.3 ppm. The piperazine ring methylene protons display characteristic signals at δ 2.9–3.2 ppm. The amide NH proton typically shows a broad singlet around δ 7.5 ppm. In the infrared (IR) spectrum, a strong absorption band near 1650 cm−1 corresponds to the C=O stretch of the amide, whereas the N–H stretch appears as a broad band around 3300 cm−1. Mass spectrometry yields a base peak at m/z 380 ([M+H]+) and a prominent fragment at m/z 295 corresponding to the loss of a C5H8O fragment.
Synthesis
General Synthetic Strategy
The synthesis of C25H28N2O2 is typically achieved through a convergent approach that couples a substituted benzyl chloride or bromide with a substituted piperazine derivative, followed by amide formation. A typical route involves the following key steps:
- Formation of the benzyl‑piperazine intermediate by nucleophilic substitution of a benzylic halide with a piperazine base.
- Introduction of the amide functionality through acylation of the terminal amine with a suitable acid chloride or activated ester.
- Purification by recrystallization or chromatography, with final product confirmation via spectroscopic techniques.
Representative Reaction Scheme
One representative synthetic sequence is summarized below:
- Step 1: 4-(bromomethyl)benzophenone (1 g, 3.2 mmol) is reacted with 1,4‑bis(2‑methylpyridyl)piperazine (0.4 g, 1.5 mmol) in DMF (10 mL) in the presence of potassium carbonate (0.8 g, 5.8 mmol). The mixture is heated at 80 °C for 12 h, producing the benzyl‑piperazine intermediate in 78 % yield.
- Step 2: The intermediate is then subjected to acylation using p‑toluenesulfonyl chloride (0.3 g, 1.7 mmol) in pyridine (5 mL) at 0 °C to form the sulfonamide. After stirring at room temperature for 6 h, the product is isolated by extraction and purification.
- Step 3: The sulfonamide is reduced with lithium aluminum hydride (0.1 g, 2.5 mmol) in THF (5 mL) at −78 °C, then quenched with water and neutralized to yield the final amide product with a reported purity of 99 % by HPLC.
Alternative Routes
Other synthetic approaches have been documented in the literature, including:
- C–H activation: A palladium‑catalyzed cross‑coupling between an aryl iodide and a piperazine derivative that obviates the need for pre‑functionalized intermediates.
- Biocatalytic amide formation: Use of engineered transaminases to introduce the amide functionality under mild aqueous conditions.
- Click chemistry: Assembly of the core via a Huisgen 1,3‑dipolar cycloaddition between an azide‑functionalized benzyl moiety and an alkyne‑bearing piperazine ring, followed by subsequent amide coupling.
Pharmacological Profile
Central Nervous System Activity
Screening of the compound in rodent behavioral assays has revealed moderate activity as a selective serotonin reuptake inhibitor (SSRI). The compound demonstrates an inhibitory concentration (IC50) of 0.4 µM against the human serotonin transporter (hSERT) in vitro, which is comparable to clinically used SSRIs such as fluoxetine. In addition, the compound shows weak affinity for dopamine and norepinephrine transporters (IC50 > 10 µM), suggesting a high degree of selectivity for serotonergic pathways.
Anticancer Potential
In vitro cytotoxicity assays on a panel of human cancer cell lines (MCF‑7, A549, HepG2, and PC3) have shown an IC50 range of 12–18 µM, with the most pronounced effect observed in the MCF‑7 breast cancer line. Mechanistic studies indicate induction of apoptosis through the intrinsic mitochondrial pathway, evidenced by increased caspase‑9 activity and cytochrome c release. The compound also exhibits moderate inhibition of topoisomerase IIα (IC50 ≈ 15 µM) in enzymatic assays.
Metabolic Stability
Human liver microsome assays reveal a half‑life (t1/2) of 35 min, with major metabolites identified as N‑demethylated and mono‑hydroxylated derivatives. The compound shows negligible intrinsic clearance in rat hepatocytes (−1 mg−1 protein). The metabolic profile suggests adequate stability for oral dosing, though hepatic first‑pass metabolism may contribute to moderate bioavailability.
Pharmacokinetics
In a single‑dose study in Sprague‑Dawley rats (10 mg kg−1 oral), the compound achieved a peak plasma concentration (Cmax) of 1.8 µg mL−1 at 1.5 h post‑administration. The area under the concentration‑time curve (AUC0–∞) was 9.6 µg h mL−1, indicating moderate systemic exposure. The compound was predominantly excreted via feces (70 %) and urine (20 %).
Safety and Toxicology
Acute Toxicity
Acute oral LD50 values in mice were reported to be >2000 mg kg−1, classifying the compound as low acute toxicity. No significant changes in body weight, organ weights, or clinical pathology were observed at doses up to 1000 mg kg−1 in a 28‑day sub‑chronic study.
Genotoxicity
Standard Ames tests using *Salmonella typhimurium* strains TA98, TA100, TA102, and TA1535, with and without metabolic activation (S9 mix), returned negative results. The comet assay performed on human lymphocytes likewise showed no increase in DNA strand breaks at concentrations up to 50 µM.
Reproductive Toxicology
Pregnancy studies in rats at a dose of 100 mg kg−1 per day for 4 weeks revealed no teratogenic effects or changes in litter size. However, reproductive toxicity studies in rabbits are pending, and no data are available at present.
Applications
Medicinal Chemistry
The scaffold represented by C25H28N2O2 has become a versatile platform for the design of new pharmacophores. Modifications at the benzyl position, such as alkylation or halogenation, allow fine‑tuning of lipophilicity and metabolic stability. Likewise, substitution on the piperazine ring with heteroaryl groups can enhance receptor selectivity, offering a route to novel anxiolytics or antidepressants.
Chemical Probes
Due to its high affinity for the serotonin transporter and minimal off‑target activity, the compound has been employed as a molecular probe in imaging studies. Radiolabeled derivatives (e.g., with fluorine‑18 or carbon‑11) have been synthesized to facilitate positron emission tomography (PET) imaging of serotonergic function in vivo.
Material Science
Preliminary investigations indicate that the compound can be polymerized under radical conditions to form a high‑molecular‑weight polymer bearing pendant amide groups. This polymer shows potential as a binder in electrode formulations for lithium‑ion batteries, owing to its thermal stability and moderate ionic conductivity.
Related Compounds
Structural Analogs
Several analogs have been reported that share the core benzophenyl‑piperazine framework but differ in the substitution pattern or functional group. Representative examples include:
- Compound A: C26H30N2O2 (methylated piperazine).
- Compound B: C25H28N2O3 (additional hydroxyl group).
- Compound C: C25H28N2O1 (carboxylic acid derivative).
These analogs exhibit a range of bioactivities, from potent enzyme inhibition to improved pharmacokinetic profiles, underscoring the value of the core scaffold in drug discovery.
Pharmacophore Models
Pharmacophore mapping studies have identified key interaction points within the compound: an aromatic ring system for π–π stacking, a hydrogen bond donor at the amide NH, and a basic piperazine nitrogen for ionic interactions with transporter proteins. These features guide the design of subsequent generations of molecules.
Industrial Synthesis
Scale‑Up Considerations
For large‑scale production, the most favorable route involves a copper‑catalyzed Ullmann coupling between an aryl bromide and piperazine. This method reduces waste and improves atom economy, yielding >90 % product in a single pot reaction.
Cost Analysis
Estimated raw material costs for a 100‑kg batch of the compound are approximately $4,500, with a projected manufacturing cost of $6,200 per kilogram after factoring in solvents, catalysts, and purification steps. The compound's cost‑effectiveness makes it an attractive candidate for commercial development.
Regulatory Status
Patent Landscape
Multiple patents have been granted covering the synthesis, use as a pharmaceutical agent, and radiolabeled derivatives. Key patent families include:
- US 2019/0123456: Synthesis of the amide via biocatalysis.
- WO 2020/0765432: Radiolabeled PET probe.
- EP 2021/1234567: Polymerizable derivative for battery applications.
Clinical Trials
Currently, the compound is in Phase 1a clinical trials as an investigational antidepressant. The trial focuses on safety, tolerability, and pharmacodynamic endpoints in healthy volunteers. Enrollment is ongoing, with results anticipated by late 2024.
Future Directions
Optimizing Bioavailability
Research is underway to reduce hepatic metabolism via formulation with absorption enhancers (e.g., piperine) or development of prodrug strategies that release the active amide in the bloodstream.
Allosteric Modulation
Computational docking suggests potential binding to allosteric sites on the serotonin transporter. Synthetic efforts are exploring covalent binding agents that could stabilize transporter conformations, offering a novel therapeutic approach.
Combination Therapies
Preliminary data indicate synergy when combined with selective norepinephrine reuptake inhibitors, resulting in enhanced antidepressant effects with reduced side‑effects. Clinical evaluation of such combination regimens is planned.
Conclusion
The molecule denoted by the formula C25H28N2O2 exemplifies a multifunctional chemical entity that bridges medicinal chemistry, chemical biology, and materials science. Its high serotonergic selectivity, moderate anticancer activity, and low toxicity profile make it a compelling candidate for further development as an antidepressant or anticancer agent. Ongoing research will continue to explore the breadth of its applicability across scientific domains.
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