Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester

Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester is a Boc-protected asymmetric diamine that serves as a key synthetic intermediate in medicinal chemistry, bioconjugation, and polyamine research. Chemically, Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester is a selectively protected spermidine derivative (N⁴-Boc-spermidine), where the central secondary amine of the natural polyamine spermidine has been masked with a tert-butoxycarbonyl group, leaving the two terminal primary amines free for selective derivatization. In organic synthesis, Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester functions as a Boc-protected spermidine building block for the construction of polyamine-containing peptides, polyamine-drug conjugates, and macrocyclic polyamine derivatives with applications spanning antimicrobial, anticancer, and gene delivery research. Its value lies in the ability to perform sequential, chemoselective transformations at the two primary amines while the central Boc-protected nitrogen remains inert, then later deprotect the Boc group under mild acidic conditions to reveal the secondary amine for a third orthogonal functionalization or to regenerate the native spermidine scaffold—a strategy of critical importance for the precise assembly of complex, polyfunctional target molecules where regiochemical control is paramount.

Product Parameters

Product Advantages

1.Trifunctional Building Block with Chemoselective Reactivity

Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester features three distinctly reactive nitrogen centers: two terminal primary amines and one Boc-protected tertiary amine. The two primary amines exhibit similar intrinsic nucleophilicity yet differ in their steric accessibility due to the asymmetric spacer lengths (C4 vs. C3), enabling finely tuned chemoselective acylations, reductive aminations, or conjugate additions under optimized conditions. Meanwhile, the Boc-protected nitrogen remains completely inert, serving as a latent secondary amine that can be unveiled under acidic conditions after the primary amines have been functionalized.

2. Boc Protection Enables Orthogonal Synthetic Strategies

The tert-butoxycarbonyl (Boc) protecting group in Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester is among the most widely adopted amine protecting groups in organic synthesis. It provides excellent stability under basic, nucleophilic, and hydrogenolytic conditions, yet undergoes clean, quantitative cleavage under mild acidic conditions—typically 20–50% trifluoroacetic acid (TFA) in dichloromethane or 4M HCl in dioxane—without affecting ester, ether, amide, or carbamate functionalities elsewhere in the molecule. This orthogonality is indispensable for the convergent assembly of complex, polyfunctional architectures.

3. Directly Derived from the Natural Polyamine Spermidine

As N⁴-Boc-spermidine, Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester is the direct Boc-protected derivative of spermidine—an endogenous polyamine found in all living cells that plays essential roles in cell growth, proliferation, and nucleic acid stabilization. Spermidine-derived compounds have been extensively investigated for their autophagy-inducing, neuroprotective, and anti-aging properties, as well as for the construction of polyamine-drug conjugates that exploit the polyamine transport system (PTS) for selective cellular uptake. The availability of the Boc-protected form enables the systematic exploration of spermidine's therapeutic potential through controlled chemical modification.

4.Versatile Intermediate for Polyamine-Drug Conjugates

The two free primary amines of Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester can be selectively conjugated to drug payloads, fluorescent probes, targeting ligands, or PEG chains, while the central Boc group remains intact. Subsequent Boc deprotection reveals the secondary amine, which can be further functionalized or protonated under physiological conditions to restore the cationic polyamine character of the spermidine scaffold—a critical feature for DNA/RNA binding, cellular uptake via the polyamine transport system, and endosomal escape in gene delivery applications.

5.Gateway to Macrocyclic and Supramolecular Architectures

Through sequential derivatization of the three nitrogen centers, Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester serves as a precursor to a diverse array of macrocyclic polyamines, cryptands, and cage-like structures. These nitrogen-rich macrocycles find application as metal-chelating agents for diagnostic imaging (MRI contrast agents, PET radiopharmaceuticals), as anion receptors in supramolecular chemistry, and as scaffolds for the construction of enzyme mimetics and catalytic antibodies.

Synthetic Route

The synthesis of Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester has been documented in the literature via selective Boc protection of spermidine.

A representative synthetic approach involves the reaction of spermidine (N-(3-aminopropyl)butane-1,4-diamine) with di-tert-butyl dicarbonate (Boc₂O) under carefully controlled stoichiometric conditions. The key challenge lies in achieving selective mono-Boc protection at the central secondary amine (N⁴ position) while leaving the two terminal primary amines unaffected. This selectivity is typically achieved by exploiting the differential nucleophilicity and steric accessibility of the three nitrogen atoms in spermidine. Under optimized conditions—often employing low temperatures (0 °C), slow addition of Boc₂O (approximately 1.0 equivalent), and the presence of a mild base such as triethylamine or N,N-diisopropylethylamine (DIEA) in a suitable solvent (dichloromethane, methanol, or dioxane/water mixtures)—the secondary amine reacts preferentially due to its higher nucleophilicity compared to the ammonium ion forms of the primary amines at neutral pH. The reaction progress is monitored by TLC (visualized with ninhydrin or potassium permanganate stain), and the crude product is purified by silica gel column chromatography or recrystallization to afford Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester with typical purity exceeding 97%.

The product is characterized by ¹H NMR spectroscopy, where the diagnostic tert-butyl singlet appears at approximately δ 1.44 ppm (9H), and the methylene protons adjacent to the carbamate nitrogen resonate in the region of δ 3.10–3.30 ppm. High-resolution mass spectrometry confirms the molecular ion [M+H]⁺ at m/z 246.2176 (calculated) and 246.2172 (measured).

Storage Conditions

Store Carbamic acid, N-(4-aminobutyl)-N-(3-aminopropyl)-, 1,1-dimethylethyl ester at –20 °C in a tightly sealed container under an inert atmosphere of nitrogen or argon. The compound should be protected from light and moisture at all times. Allow the sealed package to equilibrate to ambient temperature before opening to prevent moisture condensation. The free primary amine groups are susceptible to oxidation and to absorption of atmospheric carbon dioxide (forming carbamate salts), which can compromise purity and reactivity; therefore, storage under anhydrous, inert conditions is essential for maintaining long-term integrity. The Boc protecting group is stable under recommended storage conditions but is susceptible to thermal deprotection at elevated temperatures (above ~150 °C). Adherence to the storage recommendations specified in the Certificate of Analysis is essential for preserving product quality throughout its documented shelf life.

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