What Is Quinuclidine Amine? A Structure Analysis, Application Taxonomy, and Reagent Selection Navigator Centered on 3-Aminoquinuclidine (Tables 1–3)

“Quinuclidine amine” commonly refers to quinuclidin-3-amine / 3-aminoquinuclidine and its salts (especially the dihydrochloride). Its parent scaffold, quinuclidine, is 1-azabicyclo[2.2.2]octane, a typical bridged/caged amine structure.

This article uses the most commonly employed research building block—quinuclidin-3-amine (3-aminoquinuclidine)—as the core entry, and also includes quinuclidin-4-amine as a key positional isomer control for comparing spatial orientation and structure–activity differences.

1.Name Clarification: Quinine ≠ Quinuclidine ≠ Quinuclidine Amine

English / System name	Core meaning
Quinine	A Cinchona alkaloid; commonly discussed in antimalarial contexts (not the focus here).
1-azabicyclo[2.2.2]octane	A strongly basic amine scaffold with a “bridgehead N + caged bicyclic” framework.
quinuclidin-3-amine / 3-Aminoquinuclidine	A derivative formed by introducing –NH₂ at the 3-position of the quinuclidine framework (often supplied as a salt).

2.Basic Concept: What Does the “Quinuclidine Amine” Structure Look Like?

Using the most common 3-aminoquinuclidine as an example, you can understand it as:

1. Core scaffold: Quinuclidine = a “locked triethylamine-like” caged amine (the bridgehead nitrogen is a tertiary amine site).

2. External handle: An additional –NH₂ (a primary amine) extends from the 3-position, making it a dual-nitrogen system (one bridgehead tertiary amine + one external primary amine).

Common commercial forms and enantiomers of 3-Aminoquinuclidine (quinuclidin-3-amine)

Form	Common name	Typical CAS	Notes
Free base	3-Aminoquinuclidine (quinuclidin-3-amine)	6238-14-8	Strongly basic and hygroscopic; readily forms salts with acids. In practice, it is often supplied and used as a salt.
Dihydrochloride (most common)	3-Aminoquinuclidine dihydrochloride	6530-09-2	The most commonly marketed form; solids are easier for weighing, storage, and shipping (often hygroscopic—store tightly sealed).
Enantiomer (3S) dihydrochloride	(S)-(−)-3-Aminoquinuclidine·2HCl (also written as (3S)-)	119904-90-4	Used when downstream synthesis/intermediates require a specific configuration; confirm both configuration and salt form.
Enantiomer (3R) dihydrochloride	(R)-(+)-3-Aminoquinuclidine·2HCl (also written as (3R)-)	123536-14-1	Mirror image of the 3S enantiomer and not interchangeable; used for routes or control studies requiring the 3R configuration.

3.Structural Features

3.1 Cage-like rigidity enables a predictable 3D shape

The quinuclidine framework is a classic bridged/caged structure: it is highly rigid with low conformational freedom, and is often used to lock a positive-charge center / hydrogen-bond acceptor into a defined spatial position. “Increasing rigidity via ring frameworks” is a common rational strategy in drug design.

3.2 Strong basicity and easy salt formation make cationic interactions more reliable

The bridgehead tertiary amine of quinuclidine has a conjugate-acid pKa (in water) on the order of ~11, so it can stably provide a protonated cationic center and facilitate reliable ion-pair/salt-bridge interactions. For 3-aminoquinuclidine, in addition to the bridgehead tertiary amine, the external primary amine at C3 can also participate in protonation and salt formation (depending on solvent, ionic strength, and reaction system). Therefore, in commercial supply and routine handling, salt forms such as the dihydrochloride (·2HCl) are common to improve practicality for weighing, storage, and transportation.

3.3 “Two nitrogen sites” = both a scaffold and a connection handle

1. Bridgehead tertiary amine: mainly serves as a basic center / recognition element / site for quaternization. Because it is a tertiary amine, it is typically not used as the reaction site for amidation or sulfonylation (it is difficult to form stable N-acyl/N-sulfonyl derivatives); such derivatizations are generally performed on the external primary amine.

2. C3 primary amine: a highly practical “chemical connection handle,” enabling amide formation, urea/thiourea formation, sulfonamide formation, reductive amination, etc., to rapidly incorporate the quinuclidine scaffold into target molecules.

3.4 Stereochemistry: the C3 stereocenter and enantiomer selection

When an –NH₂ (or other substituent) is introduced at C3, that carbon becomes a stereocenter, and the compound typically exists as an enantiomeric pair (3R and 3S). In synthesis and applications, the required configuration (e.g., (3R)- or (3S)-3-aminoquinuclidine) should be explicitly specified, because different enantiomers may show markedly different behavior in downstream reactions, SAR, and biological activity. In chiral drug-intermediate routes, selecting the wrong starting enantiomer often leads to configuration mismatch, requiring additional resolution steps or route rework.

Note: (+)/(−) indicates the direction of optical rotation and may vary with salt form and measurement conditions; for route design and SAR discussions, rely on the C3 CIP (Cahn–Ingold–Prelog) configuration assignment (3R/3S).

4.Where Are Quinuclidine Amines Commonly Used?

Application area	Typical research task	Key problem solved by quinuclidine amines
Drug-synthesis intermediates (especially 5-HT₃ receptor ligand routes)	Incorporating a “rigid 3D amine fragment” into a target drug scaffold	Provides a fixed cationic center + a derivatizable –NH₂ handle, facilitating formation of key amide/amine intermediates
Receptor/ion-channel ligands and SAR studies	Using spatially controlled amine fragments to improve affinity/selectivity	The caged scaffold reduces conformational freedom, making SAR more interpretable; the bridgehead amine offers stable charge interactions
Quaternary ammonium salts / functional cationic materials & antibacterial research	Building new QACs and evaluating antibacterial activity	Quinuclidine can serve as a “QAC core,” with activity/properties tuned via side-chain length and substitution

5.How to Classify Quinuclidine Amines

5.1 Classification by enantiomer and salt form

Classification dimension	Common options	When to prioritize
Enantiomer	Racemate / (R) / (S)	If the target is a chiral drug intermediate, or if downstream reactions/evaluations are stereosensitive, you must specify the enantiomer (R or S) and enantiomeric purity; choose racemate only when configuration is not distinguished or for early screening.
Form	Free base / monohydrochloride / dihydrochloride	For routine storage, shipping, and weighing, salts (often HCl salts/2HCl) are usually more stable and easier to handle; when higher nucleophilicity is needed for amidation/sulfonylation/reductive amination, it is recommended to release the salt to the free amine before reaction (commonly by basification and extraction, or in-situ neutralization with an appropriate base) to ensure reactivity and controllable equivalents.

5.2 Classification by derivatization direction

Target derivative type	Key reaction entry point	Typical purpose
Amides / ureas / sulfonamides / guanidines, etc. (C3 side-chain derivatization)	Use the external C3 –NH₂ (primary amine) for acylation, sulfonylation, isocyanate addition (ureas), guanidinylation, etc.	Rapidly connect the quinuclidine scaffold to pharmacophores or linkers via a “connection handle”; commonly used to build series for SAR or property optimization
Quaternary ammonium salts (QAC; permanent cation)	Use the bridgehead tertiary amine for N-alkylation/quaternization (often combined with C3 derivatization: first make C3 amides, then quaternize)	Builds a stable cationic center for antibacterial activity studies and mechanistic probes; also used for functional cationic/ionic material design (tuning hydrophilicity/hydrophobicity, membrane interaction, ion transport, etc.)

6.When Should You Choose a Quinuclidine Amine?

If your project meets any of the following, a quinuclidine amine is often a high-value candidate fragment:

1. You need a strong, stable cationic center to form ion pairs/salt bridges with receptors, while keeping conformation more controllable.

2. You need a rigid 3D amine fragment + a connectable handle: it provides key charge features and enables rapid library construction via the –NH₂ handle.

3. You are working on palonosetron or related 5-HT₃ antagonist routes (or impurities/reference standards) and require the corresponding enantiomer of 3-aminoquinuclidine as a key starting unit.

7.Reagent Selection Navigator for Quinuclidine Amines (3-Aminoquinuclidine) (Tables 1–3)

Scenario tag	Research task / experimental need	Recommended table to check first	Representative products (Aladdin Cat. No.)	Selection logic
Chiral synthesis	Chiral drug/intermediate routes requiring explicit (R)/(S) configuration	Table 2: Quinuclidine-amine building blocks (C3/C4; incl. enantiomers)	R132220 / A123962 / Q698806	C3 is a stereocenter; enantiomer choice affects downstream matching of target configuration—lock the needed enantiomer and salt form first.
Library building / methodology	Rapid derivatization library (amides/sulfonamides/ureas, etc.) without emphasizing chirality	Table 2: Quinuclidine-amine building blocks (C3/C4; incl. enantiomers)	A151272	Racemic dihydrochloride is most common and easy to weigh/store; suitable as a general starting amine for derivative libraries.
Route development	Starting from upstream precursors to functionalize at C3 (reductive amination / conversion to amine, etc.)	Table 1: Upstream precursors & parent scaffolds (incl. salts)	Q109701	3-Quinuclidone HCl is a high-frequency entry for C3 derivatization; choosing the right precursor can determine route feasibility and yield window.
Base/scaffold control	Using quinuclidine as a strong base, or as QAC/salt-form controls	Table 1: Upstream precursors & parent scaffolds (incl. salts)	Q132740 / Q469170	Free base vs HCl salt map to “reactivity vs handling stability”; useful for controls and process reproducibility.
Positional isomer control	Comparing C3 amine vs C4 amine (orientation differences driving SAR changes)	Table 2: Quinuclidine-amine building blocks (C3/C4; incl. enantiomers)	A1031288 + (control) A151272/Q698806	The C4 amine is a key positional isomer control, helping assess how “amine position/linker orientation” impacts activity/properties.
Drug reference / bioassays	5-HT₃ experiments, quantitative methods, cell/receptor assays using reference standards	Table 3: Downstream drug references (ready-to-use/solid)	P129744 / P421357	Choose standards that are directly usable for quantitation or bioassays; solutions speed preparation/HTS, solids support long-term storage and accurate quantitation.

Table 1｜Upstream Precursors and Parent Scaffolds (incl. salts)

Category	CAS	Aladdin Cat. No.	Name	Specification/Purity	Key features & applications
Key upstream precursor (entry for C3 functionalization)	1193-65-3	Q109701	3-Quinuclidone hydrochloride	≥99%	A high-frequency precursor for C3 functionalization; commonly used to prepare C3-substituted quinuclidine derivatives (e.g., reductive amination, oxime formation–reduction), providing a general entry to 3-aminoquinuclidine and its derivatives.
Parent base (quinuclidine scaffold)	100-76-5	Q132740	Quinuclidine	≥97%	A classic caged tertiary-amine base; can be used as a strong base/scaffold control, and also for building quaternary ammonium salts (introducing a permanent cationic center) and functional cationic materials.
Parent salt (stable supplied form)	39896-06-5	Q469170	Quinuclidine hydrochloride	≥97%	A stable salt form of quinuclidine for convenient storage, weighing, and preparation; suitable for salt-form controls or scenarios requiring in-situ release of the free base, improving experimental reproducibility.

Table 2｜Quinuclidine-Amine Building Blocks (C3/C4; incl. enantiomers)

Category	CAS	Aladdin Cat. No.	Name	Specification/Purity	Key features & applications
Chiral building block (3-aminoquinuclidine, R enantiomer; dihydrochloride)	123536-14-1	R132220	(R)-(+)-3-Aminoquinuclidine Dihydrochloride	≥98%	A (3R) chiral source of the rigid “caged amine” fragment; commonly used in chiral drug/intermediate synthesis and in enantiomer-difference control studies (activity/selectivity).
Chiral building block (3-aminoquinuclidine, R enantiomer; free base)	123536-15-2	Q698806	(R)-Quinuclidin-3-amine	≥98%	The (3R) free amine is more convenient for direct amidation/sulfonylation/urea formation and reductive amination; used to rapidly connect the quinuclidine scaffold to pharmacophores/linkers to build derivative libraries.
Chiral building block (3-aminoquinuclidine, S enantiomer; dihydrochloride)	119904-90-4	A123962	(S)-(−)-3-Aminoquinuclidine dihydrochloride	≥98%	A (3S) chiral source of the rigid “caged amine” fragment; used for stereosensitive synthesis routes and enantiomer control experiments.
Positional isomer control (4-aminoquinuclidine; dihydrochloride)	18339-49-6	A1031288	1-Azabicyclo(2.2.2)octan-4-amine dihydrochloride	≥97%	A C4 amino positional isomer; used for “C3 vs C4 substitution” SAR controls, linker-orientation comparisons, and validation of binding-site positioning hypotheses.
Racemic building block (3-aminoquinuclidine; dihydrochloride)	6530-09-2	A151272	3-Aminoquinuclidine Dihydrochloride	≥98%(T)	A general racemic building block; suitable for early screening/method development and derivatization libraries (amides/ureas/sulfonamides). As a stable salt, it is convenient for weighing and storage.
Chiral building block (3-aminoquinuclidine, S enantiomer; verify form per COA)	120570-05-0	Q690449	(S)-Quinuclidin-3-amine	≥98%	The (3S) building block for chiral routes/enantiomer controls; when ordering and calculating equivalents, confirm salt form and content information in the COA/SDS to ensure accurate equivalence and reproducible reactions.

Table 3｜Downstream Drug Reference Standards (Palonosetron)

Category	CAS	Aladdin Cat. No.	Name	Specification/Purity	Key features & applications
Downstream drug/reference (solid)	135729-62-3	P129744	Palonosetron HCl	≥99%	A classic 5-HT₃ receptor antagonist API/reference; used for receptor binding/functional assays, HPLC/LC-MS quantitative method development, and impurity/QC references.
Downstream drug/reference (ready-to-use solution)	135729-62-3	P421357	Palonosetron HCl	10 mM in Water	A pre-made 10 mM aqueous solution for cell/receptor functional assays and high-throughput screening; reduces weighing error and improves batch-to-batch consistency.

For more related articles, please see below:

Cinchona Alkaloids

Chiral Amines in Asymmetric Synthesis: Role Map (A–F), a Minimal Evidence Chain, and a Research Selection Guide (with Tables 1–3)

Cinchona Alkaloid Chiral Toolbox: Selection & Troubleshooting from Pseudoenantiomer Switching to PTC/Sharpless AD/Chiral Resolution (including Product Tables A–D)