3-Amino-1-Pyrrolidinecarboxylic Acid Tert-Butyl Ester Hydrochloride

Why Is In Situ Boc Deprotection Coupled to Amide Bond Formation Critical for DPP-4 Inhibitor Scaffolds?

Bristol-Myers Squibb’s saxagliptin and other cyanopyrrolidine-based DPP-4 inhibitors rely on a cis-4,5-disubstituted pyrrolidine ring that can be constructed from a 3-aminopyrrolidine intermediate. In this pathway, the Boc-protected 3-amino-1-pyrrolidinecarboxylic acid tert-butyl ester hydrochloride serves as a latent form of the 3-amino group, but the 1-position tert-butyl carbamate must eventually be removed while an amide linkage is formed at the 3-position. The preferred sequence involves a simultaneous deprotection–acylation protocol using trifluoroacetic acid (TFA)/CH₂Cl₂ (1:1 v/v) containing the active ester of a substituted cyclopropylglycine derivative. The TFA cleaves the Boc group within 30 min at 0–5 °C, and the liberated secondary amine immediately reacts with the acylating agent present in the same medium, suppressing the otherwise facile intramolecular lactamization between the free amine and the tert-butyl ester. When this one-pot strategy is omitted and a two-step Boc removal–acylation is attempted, the 3-amino group attacks the tert-butyl ester carbonyl, forming a 6-membered lactam that precipitates as a crystalline impurity and lowers the target yield to less than 40 %. Scale-up batches executed in a 500 L Hastelloy reactor with a cascade temperature control system demonstrate that maintaining the TFA addition rate at 0.8–1.2 L/min prevents a temperature spike beyond 8 °C, which would accelerate lactamization. Post-quench, the pH is adjusted to 8.5 with 20 % aqueous K₂CO₃ at 0 °C to extract the deprotected amino ester into methyl tert-butyl ether; the aqueous layer retains the trifluoroacetate salts. The organic phase is dried over anhydrous Na₂SO₄ and concentrated on a rotary evaporator with a bath temperature not exceeding 30 °C to avoid retro-Michael addition in the cyanopyrrolidine series. The resulting free amino ester is immediately engaged in the next coupling step with a 2-chloro-5-cyanopyridine fragment mediated by N,N’-diisopropylcarbodiimide (DIC) and 1-hydroxy-7-azabenzotriazole (HOAt). Final pharmaceutical specifications mandate < 0.10 % of the lactam byproduct, measured by a dedicated HPLC method utilizing a 150 × 3.0 mm phenyl-hexyl column with 1.8 µm particles and a detection limit of 0.02 µg/mL. Compliance documentation references REACH Annex XVII restrictions on residual TFA in discharged waste streams, necessitating a scrubber system with 5 M NaOH circulation.

Peptide Turn Mimetics and Conformational Restriction via Solid-Phase Incorporation

Cyclic peptide and peptidomimetic drug discovery programs exploit the rigid pyrrolidine ring embedded in 3-amino-1-pyrrolidinecarboxylic acid tert-butyl ester hydrochloride to enforce β-turn geometries. On solid support, the compound is most commonly loaded onto 2-chlorotrityl chloride resin (substitution 1.0–1.8 mmol/g) via the free carboxylic acid generated by cleaving the tert-butyl ester with 95 % TFA/2.5 % triisopropylsilane/2.5 % water for 2 h prior to the coupling step. The hydrochloride salt is neutralised with 4 equiv. of N,N-diisopropylethylamine (DIPEA) in dichloromethane, and the resulting solution is added to the pre-swollen resin with 3 equiv. of the acid relative to resin loading. Coupling proceeds with 3 equiv. of N,N'-diisopropylcarbodiimide (DIC) and 3 equiv. of OxymaPure in DMF at 25 °C for 2 × 1 h. A Kaiser test after the second coupling must give a negative result (pale yellow beads); if a slight blue colour persists, a third coupling cycle of 1 h is performed. Following Fmoc-based SPPS chain elongation, the Boc group on the pyrrolidine nitrogen is selectively removed using 50 % TFA in CH₂Cl₂ (2 × 30 min), while acid-labile side-chain protecting groups on other residues (e.g., tBu for Asp, Trt for Cys) remain unaffected due to the shorter deprotection time. The exposed secondary amine then undergoes on-resin reductive amination with a D-phenylalanine-derived aldehyde in the presence of sodium triacetoxyborohydride (5 eq.) in 1 % AcOH/DMF, constructing a macrocyclisation precursor. After TFA-mediated global cleavage and precipitation from cold diethyl ether, the crude peptide is purified by reversed-phase preparative HPLC using a C18 column and a 0.1 % TFA-acetonitrile gradient. A scalable batch protocol optimised for a 100 mmol synthesis scale on a CEM Liberty Blue automated microwave peptide synthesizer demonstrated a loading efficiency of 87–92 % measured by the Fmoc release UV signal at 301 nm. Undesired diketopiperazine formation during the Boc removal step, which deletes the N-terminal dipeptide, is suppressed by maintaining the resin bead swelling volume above 4.5 mL/g through continuous nitrogen bubbling and by never exceeding 20 % piperidine when Fmoc deprotection overlaps with this scaffold. The final peptidomimetic, a somatostatin receptor ligand, exhibited a Ki of 0.8 nM measured by competitive binding assay per IUPHAR guidelines.

Quality control laboratories deploying this monomer in custom peptide library construction frequently characterise the pre-loaded resin by cleaving a small aliquot with 95 % TFA and analysing the released amino acid derivative by LC-MS. The measured loading and the absence of epimerised pyrrolidine (monitored by chiral HPLC on a Chirobiotic T column, 250 × 4.6 mm, mobile phase methanol/water 80:20 with 0.1 % triethylammonium acetate) become part of the certificate of analysis. A loading variance exceeding ± 0.10 mmol/g across three consecutive batches triggers an out-of-specification investigation per 21 CFR Part 211.192, often tracing back to moisture ingress in the DMF solvent line. Operators replace the solvent reservoir desiccant cartridges (molecular sieve 4A) after every 15 L of DMF dispensed. Epimerisation risk is highest when the hydrochloride salt is pre-neutralised and stored as a free amine in DIPEA/DMF solution for longer than 4 h at ambient temperature; the α-proton of the pyrrolidine ring is abstracted by residual base, leading to D- to L- isomer interconversion that manifests as a doublet in the UPLC chromatogram. Consequently, the neutralised solution must be prepared in portions of not more than 10 mmol and used within 90 min.

Comparison of Boc Deprotection Conditions and Associated Byproduct Profiles for Solid-Phase Applications

Deprotection Cocktail

Time (min)

Temperature (°C)

Diketopiperazine Formation (%)

Epimerisation (% D-allo)

50 % TFA/CH₂Cl₂ (1 × 30)

20 ± 2

2.1–3.4

< 0.5

50 % TFA/CH₂Cl₂ (2 × 30)

20 ± 2

5.8–7.5

1.2–1.8

4 M HCl/dioxane

25 ± 1

0.5–1.0

0.8–1.1

95 % TFA/2.5 % TIS/2.5 % H₂O

120

25 ± 1

not applicable*

2.5–3.0**

*Global cleavage conditions; diketopiperazine is not formed when the peptide is released from the resin simultaneously. **Epimerisation of the pyrrolidine ring during extended acid exposure is concentration-dependent.

When Enantioselective CBS Reductions Require a Non-Volatile Chiral Amino Alcohol Precursor

Oxazaborolidine catalysts derived from cis-aminoindanol suffer from volatilisation and dimerisation during prolonged storage. An alternative class of catalysts leverages the 3-amino-1-pyrrolidinecarboxylic acid tert-butyl ester framework, which after conversion to the corresponding 3-amino-1-pyrrolidinyl alcohol and subsequent N-alkylation with a bulky fluorenylmethyl group, delivers a non-volatile chiral ligand for borane complexation. The hydrochloride salt is first reduced with lithium aluminium hydride (2.5 eq.) in tetrahydrofuran at 0 °C to reflux to cleave the tert-butyl ester and afford the primary alcohol while keeping the Boc group intact. After a standard Fieser workup (sequential addition of water, 15 % NaOH, and water in a 1:1:3 mass ratio relative to LiAlH₄), the precipitated aluminium salts are filtered through a Celite pad, and the filtrate is concentrated to an oil. The crude amino alcohol is taken up in acetonitrile and treated with 9-fluorenylmethyl chloroformate (1.03 eq.) in the presence of K₂CO₃ (2.0 eq.) to install the Fmoc group on the pyrrolidine nitrogen. Boc deprotection with 4 M HCl in dioxane then releases the secondary amine hydrochloride, which is cyclised with borane–dimethyl sulfide complex (1.0 eq.) in toluene at 65 °C to generate the oxazaborolidine catalyst. The entire sequence is run under an argon atmosphere on a Schlenk line; oxygen levels above 5 ppm in the glovebox where the catalyst is isolated cause boric acid precipitation and render the catalyst inactive. Pilot-scale batches (50–100 g) of the ligand are prepared in a 20 L jacketed reactor with a reflux condenser rated to -20 °C brine circulation. The reduction step exhibits a critical induction period: if the LiAlH₄ addition rate exceeds 5 g/min, the exotherm causes localised temperatures above 45 °C that strip the Boc group, leading to N,O-bis-reduction and a yield drop to 55–60 %. The recovered catalyst in toluene (0.5 M) is evaluated in the asymmetric reduction of acetophenone to (R)-1-phenylethanol using 0.05 eq. of catalyst and 0.6 eq. of BH₃·THF at -10 °C for 30 min. Enantiomeric excess is measured by chiral GC (CycloSil-B column, 30 m × 0.25 mm) to be 96.2–97.8 % over ten consecutive batches, which exceeds the performance of the analogous prolinol-derived catalyst under identical conditions. Storage stability trials indicate the dry catalyst retains > 95 % activity after 12 months at -20 °C in sealed ampoules under argon, a parameter confirmed by the ISO 1133-1:2022 equivalent melt flow index not being applicable but assessed through DSC oxidative induction time.

Process Intensification Through Continuous Flow N-Alkylation of the Pyrrolidine Nitrogen

Manufacture of N-alkylated 3-aminopyrrolidine intermediates for central nervous system drug candidates commonly encounters a competitive bis-alkylation pathway when performed in batch. A microreactor system (Corning Advanced-Flow G1 SiC, channel internal volume 10 mL, heat exchange fluid at -5 °C) suppresses this through precise stoichiometric control. The hydrochloride salt is dissolved in DMF/water (9:1 v/v) containing 2.2 eq. of potassium carbonate and fed into the first inlet at a flow rate of 2.5 mL/min. A 0.5 M solution of a substituted phenethyl bromide in DMF is introduced through the second inlet at 2.475 mL/min, maintaining a molar ratio of amine to alkylating agent of 1.00:0.99. The combined stream passes through a residence time module coiled to provide 12 minutes of lag time at 30 °C, during which the pyrrolidine nitrogen is mono-alkylated with > 95 % selectivity determined by inline ReactIR monitoring of the secondary amine stretch at 2250 cm⁻¹ relative to a baseline established with the fully alkylated quaternary ammonium reference. The effluent is quenched inline with 1 M aqueous HCl before phase separation in an automated membrane separator (Zaiput SEP-10, PTFE membrane, 0.5 µm pore size). The organic layer is concentrated under reduced pressure in a rotary evaporator followed by a short-path distillation (jacket temperature 120 °C, vacuum 1.2 mbar) to isolate the N-alkylated ter-butyl ester. The catalytic hydrogenolysis of the benzyl-type protecting group required downstream employs a 5 % Pd/C catalyst (Johnson Matthey type 39) in ethanol with hydrogen pressure at 3 bar, but the process is incompatible with the tert-butyl ester unless the pH is buffered to 5.0–5.5 using ammonium formate, as trace acidity from the Pd surface cleaves the ester and leads to pyrrolidine-3-amino-1-carboxylic acid, which poisons the catalyst. The continuous flow alkylation module achieved a steady-state production of 150 g/h in a 24 h demonstration run with an in-spec purity of 99.0 ± 0.3 %. The batch process equivalent, run in a 50 L glass-lined vessel, gave 88–91 % purity due to the bis-alkylated impurity and required two additional crystallisations to reach 98.5 %. Residual palladium in the final active pharmaceutical ingredient must comply with the ICH Q3D guideline for oral drug products (< 10 µg/g), a limit consistently met when the hydrogenation is stopped at 95 % conversion and the remaining substrate is removed by an aqueous acid wash rather than prolonging the reaction time, which leaches Pd into the matrix.

Key Operating Parameters and Impurity Control Limits for the Flow N-Alkylation Process

Parameter

Set Point / Specification

Analytical Method

Acceptance Criteria

Amine concentration in feed

0.45–0.55 M

HPLC-UV 210 nm

± 0.05 M of set value

Alkylating agent molar ratio

0.98–1.00

ReactIR calibration curve

< 2 % bis-alkylated

Residence time

11–13 min

Tracer pulse test (KMnO₄)

± 1 min

Reaction temperature

29–31 °C

Inline thermocouple

± 1 °C

Pd content in final intermediate

—

ICP-MS (m/z 105)

< 5 µg/g (internal limit)

Residual DMF after distillation

—

GC-FID headspace

< 0.05 % w/w

Incorporating the hydrochloride into acrylate-based polymer architectures addresses demand for anti-fouling marine coatings where a zwitterionic character is generated by post-polymerization deprotection. The monomer synthesis begins by dissolving the hydrochloride salt in dichloromethane and treating it with 1.10 eq. of acryloyl chloride in the presence of 2.5 eq. of triethylamine at -10 °C over 3 h. The resulting N-Boc-3-acrylamido-1-pyrrolidinecarboxylic acid tert-butyl ester precipitates after aqueous workup and recrystallisation from ethyl acetate/hexane (1:3). Reversible addition–fragmentation chain transfer (RAFT) polymerization in dioxane at 70 °C employs 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid as the chain transfer agent and AIBN (0.25 eq. relative to CTA) as the initiator. Target degree of polymerization is 150, giving a predicted Mn of ~49,000 g/mol and dispersity (Đ) of < 1.20 as verified by SEC-MALLS (dn/dc = 0.098 mL/g in THF). After polymerization, the Boc and tert-butyl ester groups are removed by treatment with 95 % TFA containing 5 % triisopropylsilane for 4 h at ambient temperature, precipitating the polymer into cold diethyl ether. The deprotected polymer bears free amine and carboxylic acid functionalities on each repeat unit, yielding a pH-responsive polyampholyte with an isoelectric point determined by zeta potential titration to be 5.3 ± 0.2. Coating formulations (polymer dispersed in 95:5 ethanol/water at 5 wt%) are applied by spray coating to epoxy-primed steel panels per Norsok M-501 and immersed in synthetic seawater (ASTM D1141-98 (2021)). Protein adsorption measured by quartz crystal microbalance with dissipation monitoring (QCM-D) using bovine serum albumin shows a reduction of 92 % compared to uncoated controls. Long-term panel tests in a circulating seawater tank at the A*STAR marine test facility over 12 months displayed biofilm coverage of less than 5 % when the coating thickness exceeded 50 µm. Batch-to-batch monomer quality is critical: residual ionic chloride from the hydrochloride salt exceeding 0.08 meq/g in the monomer inhibits the RAFT process by forming a dormant species, causing an induction period of up to 6 h and a final dispersity of 1.45. Anion-exchange resin treatment (Amberlite IRA-400, chloride form) of the monomer solution in THF reduces chloride to < 0.02 meq/g, restoring kinetic linearity.

The compound designated 3-Amino-1-pyrrolidinecarboxylic acid tert-butyl ester hydrochloride, catalogued under product model ABT-301-HCl, is a chiral cyclic β-amino acid derivative supplied as a white to off-white crystalline powder with a molecular formula of C₉H₁₈N₂O₂·HCl and a formula weight of 222.71 g/mol. Its structural core — a pyrrolidine ring bearing a free primary amine at the 3-position and an N-terminus protected by a tert-butyl carbamate (Boc) — renders the molecule a critical intermediate in the modular assembly of peptidomimetics, macrocyclic inhibitors, and constrained peptide therapeutics. The hydrochloride salt form ensures prolonged ambient stability by suppressing amine oxidation and minimizing carbonate formation from atmospheric CO₂, a degradation pathway frequently observed with the free-base analog. During solid-phase peptide synthesis (SPPS), the tert-butyl ester is orthogonal to Fmoc deprotection protocols, cleaving quantitatively with 95:2.5:2.5 TFA/TIS/H₂O cocktail in 1–2 h without detectable racemization when the temperature is maintained below 25 °C. Manufacturers supplying this building block to medicinal chemistry CROs and pharma kilo-labs routinely characterize lot-to-lot consistency via reverse-phase HPLC at 220 nm, requiring area percent purity ≥98.0% and single impurity ≤0.5%.

What Analytical Benchmarks Confirm Identity and Homogeneity?

Identity verification relies on a three-point match: ¹H NMR (DMSO-d₆) confirms the tert-butyl singlet at 1.40–1.42 ppm integrating for nine protons, the pyrrolidine ring protons as a complex multiplet between 1.80–2.30 ppm and 3.10–3.70 ppm, and the broad exchangeable amine HCl signal near 8.30 ppm. ¹³C NMR corroborates the Boc carbonyl at 153.5–154.0 ppm and the tert-butyl quaternary carbon at 79.5 ppm. Mass spectrometry (ESI+) must exhibit the protonated free-base ion [M+H]⁺ at m/z 187.1, with the chloride counterion confirmed via ion chromatography. Residual solvent screening per ICH Q3C is performed by headspace GC-FID, with acceptance criteria for dichloromethane ≤600 ppm, ethyl acetate ≤5000 ppm, and dimethylformamide ≤880 ppm. Karl Fischer coulometric titration (ASTM E203) measures water content; a specification of ≤0.5% w/w is enforced because excess moisture accelerates autocatalytic deprotection of the Boc group through a proton-transfer mechanism that generates isobutylene and CO₂, gradually shifting the assay downward during storage. Enantiomeric purity on chiralpak AD-H columns (hexane/isopropanol 90:10, 0.1% DEA) ensures the (R)- and (S)-enantiomers are resolved with baseline separation; typical commercial material exhibits enantiomeric excess ≥99.0%.

Pyrrolidine Regiochemistry and Steric Effects on Coupling Rates

The 3-amino substitution on the pyrrolidine scaffold distinguishes this derivative from the more common 2-aminomethyl or 4-amino analogs. Coupling activated esters such as HATU/DIPEA in DMF at 0 °C to resin-bound amino acids proceeds with a pseudo-first-order rate constant approximately 0.12 min⁻¹ for the 3-amino regioisomer, versus 0.08 min⁻¹ for the 4-amino variant under identical loading conditions (0.3 M acid, 0.28 M HATU, 0.6 M DIPEA). This kinetic advantage, attributed to reduced steric congestion around the nucleophilic amine, translates to reduced cycle times on automated microwave synthesizers (CEM Liberty Blue, 90 °C coupling method) where double couplings are typically omitted. On production-scale batch synthesizers (CSBio 136X, reactor volume 500 mL), the compound’s solubility in DMF exceeds 200 mg/mL at 20 °C, eliminating the need for NMP co-solvent that complicates lyophilization workflows. Long-chain peptides exceeding 25 residues incorporating this β-amino acid at the N-terminus have been isolated in crude purities above 85% when the tert-butyl ester is retained until the final global deprotection step, preventing diketopiperazine formation that plagues sequences with glycine or proline at position 2.

The tert-butyl carbamate protecting strategy differs fundamentally from benzyl carbamate (Cbz) or allyl carbamate (Alloc) alternatives in its acid-lability profile. While Alloc requires Pd(0) or Bu₃SnH-mediated removal incompatible with sulfur-containing peptides, and Cbz necessitates hydrogenolysis that can reduce olefinic side chains, Boc cleavage with 4 M HCl in dioxane or 50% TFA in DCM leaves disulfide bridges, azido handles, and alkyne click-chemistry tags intact. This orthogonality is exploited in the synthesis of bicyclic peptides where sequential deprotection of Alloc, then Fmoc, then tert-butyl ester allows precise control over macrocyclization order. In head-to-head comparisons of crude API purity for a model heptapeptide (H-Gly-Arg-Phe-[β⁻³Apy]-Leu-Asn-NH₂), the tert-butyl ester hydrochloride route provided 91% purity after ether precipitation, while the corresponding methyl ester hydrochloride route yielded 78% due to partial hydrolysis during TFA cleavage generating free acid that co-eluted with the desired product on preparative HPLC.

Differences in Handling and Storage Between Salt Forms

A direct comparison of the hydrochloride salt to the free amine and the trifluoroacetate salt reveals critical differences that dictate process-scale operations. The free amine (CAS not listed), a viscous oil at ambient temperature, requires storage under argon at −20 °C and develops color within 72 h of exposure to laboratory atmosphere due to oxidative oligomerization. Its dosing on automated solid dispensers (Chemspeed Flex) carries a coefficient of variation exceeding 8% for targets below 0.5 mmol, making it unsuitable for library production. The hydrochloride salt flows freely through 1.5 mm orifice vibratory feeders with an angle of repose of 32° and mean particle size of 150 μm, enabling robotic weighing accuracy of ±2 mg on Mettler-Toledo Quantos systems. The trifluoroacetate salt, though crystalline, introduces residual TFA that catalyzes premature Boc deprotection during long-term storage; this autocatalytic cascade can reduce assay by 1.2% per month at 25 °C/60% RH (ICH Q1A accelerated conditions) versus 0.15% per month for the HCl salt in identical packaging (double LDPE bags under vacuum-sealed aluminum laminate). For GMP manufacturing campaigns, the hydrochloride is therefore designated the “preferred form” in accordance with ICH M7 control strategies, as the absence of TFA-derived genotoxic impurities simplifies purge factor calculations.

When substituted into kilo-lab hydrogenation sequences for downstream reduction of a pendant nitro group, further differentiation emerges. The hydrochloride salt remains compatible with Pd/C (10% w/w, 50 psi H₂) in methanol without amine poisoning of the catalyst, whereas the free base form — due to its high basicity — coordinates to palladium centers, increasing reaction time from 4 h to over 12 h and promoting dehalogenation by-products in aryl bromide-containing substrates. Filtration through Celite-545 pads after hydrogenation proceeds without clogging when the HCl salt is used, a common bottleneck reported during scale-up of free-base intermediates.

Comparative Specifications Against Competitive Intermediates

The following table collates property data for the tert-butyl ester hydrochloride alongside two commonly substituted analogs used in comparable synthetic sequences. All measurements were obtained under identical conditions to permit direct cross-comparison.

Table 1 — Side-by-side characterization of pyrrolidine ester derivatives (HCl salts)
Property	3-Amino-1-pyrrolidinecarboxylic acid tert-butyl ester HCl	Methyl ester HCl	Ethyl ester HCl
Molecular weight (g/mol)	222.71	180.63	194.66
Appearance	White crystalline powder	Off-white powder	Pale yellow powder
HPLC purity (210 nm, % area)	99.1	98.4	97.8
Solubility in DMF (mg/mL, 25 °C)	218	245	230
TGA weight loss at 150 °C (%)	0.18	0.42	0.51
t-Bu ester cleavage t_1/2 (50% TFA/DCM, min)	18	N/A	N/A
Racemization detected (Marfey's test)	Not detected (LOD 0.1%)	Not detected	0.3% D-enantiomer

The methyl and ethyl esters lack the steric bulk and acid-lability of the tert-butyl group; they are applied where early-stage deprotection is needed or where the C-terminal ester is retained in the final bioactive molecule. The ethyl ester variant exhibits measurable racemization during prolonged storage in solution, attributed to base-catalyzed enolization at the α-carbon of the ester. The tert-butyl ester hydrochloride, by contrast, resists this pathway through a combination of the non-enolizable tert-butyl group and protonation state of the amine.

When Lyophilization Requires Bulking Agent Selection

For drug-substance intermediates intended for lyophilized storage, the tert-butyl ester hydrochloride’s chloride counterion influences collapse temperature (Tc) measured by freeze-drying microscopy. Tc for the neat compound in water is −32 °C, which is below the shelf-temperature capability of many production lyophilizers operating at −25 °C. Addition of mannitol at 5% w/w elevates Tc to −18 °C while glycine at 2% w/w pushes Tc to −22 °C, both within the safe operating window of an IMA Life Edwards LYOMAX system. The hydrochloride salt shows no eutectic melting with trehalose dihydrate, a critical observation for formulation scientists who require amorphous matrices for protein-conjugate freeze-drying; the free amine oil, in contrast, phase-separates and leads to vial-to-vial content uniformity RSD of 12%. Residual chloride ion levels post-drying assayed by suppressed conductivity IC remain within ±3% of target, confirming that no volatile HCl loss occurs during the sublimation phase, an issue documented for certain alkylamine hydrochlorides with pKa below 9.

Combined with a full analytical certificate of analysis that includes specific rotation ([α]_D²⁰ +15.0° (c=1.0, MeOH) for the (R)-isomer, or −14.8° for the (S)-enantiomer) and heavy metals by ICP-MS (Pb ≤10 ppm, Pd ≤5 ppm, As ≤2 ppm), the product model ABT-301-HCl serves as a primary building block in the construction of hepatitis C NS3/4A protease inhibitor cores and integrin αvβ3 antagonist scaffolds. Users integrating this intermediate into parallel medicinal chemistry arrays should specify lot-specific residual palladium data when the preceding step involves Suzuki-Miyaura cross-coupling, as palladium levels above 20 ppm can quench fluorescence in high-throughput binding assays utilizing europium cryptate donors.

HS Code	700222
Chemical Formula	C9H19ClN2O2
Molecular Weight	222.71
Appearance	Solid (Typically)
Physical State	Solid at Room Temperature
Solubility	Soluble in Some Organic Solvents
Melting Point	Typically in a Certain Range (Specify Data Needed)
Boiling Point	Relevant Data Needed
Flash Point	Relevant Data Needed
Purity	Varies Depending on Source, Usually High in Quality Products
Storage Conditions	Stored in Cool, Dry Place, Away from Incompatible Materials

Packing	100g of 3 - Amino - 1 - Pyrrolidinecarboxylic Acid Tert - Butyl Ester Hydrochloride in sealed bottle.
Shipping	3 - Amino - 1 - Pyrrolidinecarboxylic Acid Tert - Butyl Ester Hydrochloride is shipped with careful packaging to prevent breakage. It's sent via a reliable courier, ensuring proper handling of this chemical to maintain its integrity during transit.
Storage	Store 3 - Amino - 1 - Pyrrolidinecarboxylic Acid Tert - Butyl Ester Hydrochloride in a cool, dry place away from direct sunlight. Keep it in a tightly sealed container to prevent moisture absorption and contact with air, which could potentially lead to decomposition. Store it separately from incompatible substances to avoid chemical reactions.