Buy 4-ANPP despropionyl fentanyl Cas 21409-26-7
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4-ANPP, also known as 4-anilino-N-phenethylpiperidine (4-ANPP), 4-aminophenyl-1-phenethylpiperidine, or despropionyl fentanyl,[3] is a direct precursor to fentanyl and acetylfentanyl. It is commonly found as a contaminant in samples of drugs containing fentanyl, which may include samples represented by the supplier as heroin or other opioids.[4] It is not psychoactive and is present only as a result of improper chemical purification.
4-ANPP is useful in the synthesis of pharmaceuticals, primarily fentanyl and related analogs. Paul Janssen (founder of Janssen Pharmaceutica) first synthesized fentanyl in 1960 using a similar method, with Benzylfentanyl as an intermediate.[5] The following synthesis, developed by an individual under the pseudonym of Siegfried, involves the reductive amination of N–phenethyl-4-piperidinone (NPP) with aniline to make to 4-ANPP. This product is reacted with propionyl chloride or acetyl chloride to form either fentanyl or acetylfentanyl.
See also
4-ANPP is a synthetic organic compound primarily known as an immediate precursor and impurity related to fentanyl and fentanyl analogues. It is formally named 4-anilino-N-phenethylpiperidine and is also called despropionyl fentanyl. Structurally, it is a piperidine derivative with the molecular formula C19H24N2 and is very closely related to the fentanyl scaffold.
Its main use is in the chemical synthesis of fentanyl-type opioids. Because of this central role, it is regulated in many countries as a controlled drug precursor.
In practice, 4-ANPP often appears as an impurity or by-product in illegally produced fentanyl and can be detected in seized drug samples and sometimes in biological specimens. Analytical and forensic laboratories use highly pure 4-ANPP as a reference or calibration standard to identify and quantify fentanyl-related substances during chemical and toxicological analyses.
4-ANPP
An analytical reference standard categorized as an opioid and a precursor in the synthesis of fentanyl and other opioids; has been found as an impurity in illicit fentanyl preparations; regulated as a Schedule II compound in the United States; intended for research and forensic applications CAS Number: 21409-26-7 Synonyms: 4-Aminophenyl-1-phenethylpiperidine|4-Anilino-N-phenethylpiperidine|Despropionyl fentanyl Storage Temperature: -20°C Shipping Temperature: -20°C
Technical Parameters
Basic Identity
| Product Name | 1-phenethyl-N-phenylpiperidin-4-amine |
|---|---|
| CAS | 21409-26-7 |
| Synonyms | despropionylfentanyl despropionylfentanyl dihydrochloride |
| Molecular Formula | C19H24N2 |
| Molecular Weight | 280.4 g/mol |
Structural Identifiers
| SMILES | C1CN(CCC1NC2=CC=CC=C2)CCC3=CC=CC=C3 |
|---|---|
| InChI | InChI=1S/C19H24N2/c1-3-7-17(8-4-1)11-14-21-15-12-19(13-16-21)20-18-9-5-2-6-10-18/h1-10,19-20H,11-16H2 |
| InChIKey | ZCMDXDQUYIWEKB-UHFFFAOYSA-N |
Commercial & Availability
| Standard Pack Sizes | 10 mg / 50 mg / 100 mg / Bulk Custom |
|---|---|
| Availability | In Stock |
| Custom Synthesis | Available on request |
1-Phenethyl-N-Phenylpiperidin-4-Amine (4-ANPP): Fentanyl Precursor, Metabolite, and Forensic Marker
1-Phenethyl-N-phenylpiperidin-4-amine (CAS 21409-26-7), also known as 4-anilino-N-phenethylpiperidine (4-ANPP), despropionylfentanyl, and N-phenyl-1-(2-phenylethyl)-4-piperidinamine, is a synthetic piperidinamine belonging to the phenethylamine chemical class [1]. It is structurally related to the potent opioid analgesic fentanyl and is exclusively recognized as the immediate chemical precursor to fentanyl, acetylfentanyl, and related fentanyl analogs, as well as a minor hydrolytic metabolite of multiple fentanyl-based substances . As a controlled Schedule II substance in the United States and an internationally regulated precursor under the United Nations Convention against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, 4-ANPP occupies a critical intersection in pharmaceutical synthesis, forensic toxicology, and illicit drug intelligence, where its dual role as a synthetic building block and a biological metabolite necessitates rigorous chemical characterization for research, regulatory compliance, and analytical verification [2].
- [1] Wikipedia contributors. 4-ANPP. Wikipedia, The Free Encyclopedia. Last edited 2021-02-19. Accessed 2026. View Source
- [2] United Nations Commission on Narcotic Drugs (CND). Decision 60/12: Inclusion of NPP and 4-ANPP in Table I of the 1988 Convention. March 2017. Accessed 2026. View Source
Why Fentanyl Analogs Cannot Substitute for 1-Phenethyl-N-Phenylpiperidin-4-Amine in Research and Forensic Workflows
Attempting to substitute 4-ANPP with other fentanyl-related piperidinamines—such as norfentanyl (a primary metabolite), N-phenethyl-4-piperidinone (NPP, an earlier-stage precursor), or acetylfentanyl—is fundamentally flawed because 4-ANPP holds a unique position as both the immediate synthetic precursor to fentanyl and a hydrolysis product detectable across multiple biological matrices [1]. Critically, unlike fentanyl, acetylfentanyl, or most piperidinamine opioids that act as mu-opioid receptor agonists with measurable binding affinity and psychoactive potency, 4-ANPP is pharmacologically inactive and does not produce a specific pharmacological effect on the body [2]. This pharmacological inertness, combined with its distinctive occurrence pattern—elevated concentrations in illicit fentanyl preparations due to incomplete purification versus trace levels as a minor metabolite following pharmaceutical administration—provides forensic and regulatory specificity that no active opioid analog can replicate [3]. Simply put, no other fentanyl congener or metabolite simultaneously functions as a DEA-designed precursor, a metabolic biomarker with diagnostic ratios, and a synthesis-route-specific impurity marker; generic substitution therefore risks analytical misidentification, regulatory non-compliance, and loss of critical forensic intelligence.
- [1] Shanks K. Drug Primer: 4-ANPP. Axis Forensic Toxicology Blog. Updated 2024. Accessed 2026. View Source
- [2] Drug Primer: 4-ANPP. Axis Forensic Toxicology. 2024. Stating 4-ANPP is pharmacologically inactive and does not produce any specific effect on the body. View Source
- [3] Laraia N, et al. 4-ANPP: The potential caution flag for illicit fentanyl. J Anal Toxicol. 2026. DOI: 10.1093/jat/bkaf111. PMID: 41495478. View Source
Quantitative Differentiation Evidence for 1-Phenethyl-N-Phenylpiperidin-4-Amine (4-ANPP) Versus Closest Analogs
Elevated 4-ANPP Concentrations Discriminate Illicit Fentanyl from Pharmaceutical Fentanyl Source
In a large-scale study evaluating 32,723 forensic and 1,015 clinical cases positive for fentanyl, 4-ANPP blood concentrations demonstrated statistically significant elevation in postmortem (predominantly illicit) sources compared to clinical (presumed pharmaceutical) sources. Most clinical 4-ANPP concentrations (69%) were below 0.50 ng/mL, compared to only 20% of forensic cases [1]. This concentration difference provides a quantitative basis for forensic distinction that is not achievable using the active compound fentanyl alone, whose blood concentrations overlap substantially between licit and illicit use scenarios.
4-ANPP as the Highest-Prevalence Fentanyl-Related Compound in Forensic Casework, Surpassing Active Opioid Analogs
In LC-MS/MS forensic casework analyte screening covering multiple fentanyl-related compounds, 4-ANPP (the pharmacologically inactive precursor/metabolite) was the single most prevalent compound detected, surpassing even the potent active opioid fentanyl analogs furanylfentanyl and carfentanil. This paradox—an inactive compound outnumbering active drug species—underscores 4-ANPP’s unique value as a sentinel biomarker that remains detectable even when parent drugs are cleared or absent [1].
| Evidence Dimension | Detection rate (% of cases positive) across multiple fentanyl-related compounds in forensic blood/serum/urine casework |
|---|---|
| Target Compound Data | 4-ANPP detected in 56.1% of cases [1]. |
| Comparator Or Baseline | Furanylfentanyl: 44.5% of cases; Carfentanil: 25.2% of cases [1]. |
| Quantified Difference | 4-ANPP detection rate is 11.6 percentage points (1.26-fold) higher than furanylfentanyl and 30.9 percentage points (2.23-fold) higher than carfentanil. |
| Conditions | Forensic casework samples (blood, serum/plasma, urine) analyzed via LC-MS/MS across 1,563 postmortem cases investigating fentanyl analogs and novel synthetic opioids [1]. |
Why This Matters
Procurement of 4-ANPP analytical reference standards is essential because its uniquely high prevalence in forensic casework makes it a universal marker for fentanyl-related drug exposure screening, whereas active analogs like furanylfentanyl or carfentanil are less frequently detected and therefore inadequate as broad-spectrum screening targets.
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4-ANPP, also known as 4-anilino-N-phenethylpiperidine (4-ANPP), 4-aminophenyl-1-phenethylpiperidine, or despropionyl fentanyl,[3] is a direct precursor to fentanyl and acetylfentanyl. It is commonly found as a contaminant in samples of drugs containing fentanyl, which may include samples represented by the supplier as heroin or other opioids.[4] It is not psychoactive and is present only as a result of improper chemical purification. Order 4-Anilino-N-phenethylpiperidine (4-ANPP) Precursor
4-ANPP is useful in the synthesis of pharmaceuticals, primarily fentanyl and related analogs. Paul Janssen (founder of Janssen Pharmaceutica) first synthesized fentanyl in 1960 using a similar method, with Benzylfentanyl as an intermediate.[5] The following synthesis, developed by an individual under the pseudonym of Siegfried, involves the reductive amination of N–phenethyl-4-piperidinone (NPP) with aniline to make to 4-ANPP. This product is reacted with propionyl chloride or acetyl chloride to form either fentanyl or acetylfentanyl. Order 4-Anilino-N-phenethylpiperidine (4-ANPP) Precursor
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4-ANPP, also known as 4-anilino-N-phenethylpiperidine (4-ANPP), 4-aminophenyl-1-phenethylpiperidine, or despropionyl fentanyl,[3] is a direct precursor to fentanyl and acetylfentanyl. It is commonly found as a contaminant in samples of drugs containing fentanyl, which may include samples represented by the supplier as heroin or other opioids.[4] It is not psychoactive and is present only as a result of improper chemical purification. Buy 4-Anilino-N-phenethylpiperidine (4-ANPP)
4-ANPP is useful in the synthesis of pharmaceuticals, primarily fentanyl and related analogs. Paul Janssen (founder of Janssen Pharmaceutica) first synthesized fentanyl in 1960 using a similar method, with Benzylfentanyl as an intermediate.[5] The following synthesis, developed by an individual under the pseudonym of Siegfried, involves the reductive amination of N–phenethyl-4-piperidinone (NPP) with aniline to make to 4-ANPP. This product is reacted with propionyl chloride or acetyl chloride to form either fentanyl or acetylfentanyl. Order 4-Anilino-N-phenethylpiperidine (4-ANPP) Precursor
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Technical Information
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1.Pease, J.P., LePine, A.J., and Smith, C.M.Methods for preparing fentanyl and fentanyl intermediatesPatent Application PublicationUS 2013/0281702 A1(2013) 2.Watanabe, S., Vikingsson, S., Roman, M., et al.In vitro and in vivo metabolite identification studies for the new synthetic opioids acetylfentanyl, acrylfentanyl, furanylfentanyl, and 4-fluoro-isobutyrylfentanylAAPS J.19(4)1102-1122(2017) 3.Labroo, R.B., Paine, M.F., Thummel, K.E., et al.Fentanyl metabolism by human hepatic and intestinal cytochrome P450 3A4: Implications for interindividual variability in disposition, efficacy, and drug interactionsDrug Metab. Dispos.25(9)1072-1079(1997) 4.Melent’ev, A.B., Kataev, S.S., and Dvorskaya, O.N.Identification and analytical properties of acetyl fentanyl metabolitesJ. Anal. Chem.70(2)216-224(2015) 5.Steuer, A.E., Williner, E., Staeheli, S.N., et al.Studies on the metabolism of the fentanyl-derived designer drug butyrfentanyl in human in vitro liver preparations and authentic human samples using liquid chromatography-high resolution mass spectrometry (LC-HRMS)Drug Test Anal.9(7)1085-1092(2017)
4-ANPP (Item No. 18810) is an analytical reference material categorized as an opioid metabolite and a precursor in the synthesis of fentanyl (Item Nos. ISO60197 | 22659 | 14719) and other opioids. 1, 2, 3, 4, 5 4-ANPP is a metabolite of acetyl fentanyl (Item Nos. ISO60128 | ISO00128), butyryl fentanyl (Item Nos. 19734 | 14728), furanyl fentanyl (Item Nos. 19633 | 18705), acrylfentanyl (Item Nos. 23060 | 19312), and fentanyl. 1, 2, 3, 4 It has also been found as an impurity in illicit fentanyl preparations. 6 4-ANPP is regulated as a Schedule II compound in the United States.
4-ANPP (N-phenyl-1- (2-phenylethyl) -4-piperidinamine), a new opioid drug, classified as piperidinamine, synthesized as an intermediate between fentanyl from N-phenethyl-4-piperidone. 4-ANPP is a metabolite of acetylfentanil, butyrylfentanyl, furanylfentanil, acrylfentanyl and fentanyl. 4-ANPP is produced on modern chemical equipment, by professionals who know their business, which makes it clean and of high quality.
| Synonyms |
|
| IUPAC | N-phenyl-1-(2-phenylethyl)-4-piperidinamine |
| Formula | C19H24N2 |
| Molecular weight | 280.4 g/mol |
| CAS | 21409-26-7 |
| Appearance | Powder |
| Purity | ≥ 98% |
4-ANPP and other chemicals sold on this website are designed and must be used strictly for research and forensic medical examination.
Adverse properties of have not been studied.
Storage conditions of this chemical: in a cool and dry place. The stability of this chemical compound can last up to 2 years, under the right storage conditions.
4-Anilino-N-phenethylpiperidine (4-ANPP) Precursor
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