(S)-Tert-Butyl2-(2-Aminothiazol-4-Yl)Pyrrolidine-1-Carboxylate
Pyrrolidine Pyrrole Thiazole Imidazole Thiophene Pyrazine Piperidine Piperazine Morpholine Phenazine

(S)-Tert-Butyl2-(2-Aminothiazol-4-Yl)Pyrrolidine-1-Carboxylate


    • Product Name (S)-Tert-Butyl2-(2-Aminothiazol-4-Yl)Pyrrolidine-1-Carboxylate
    • Alias (S)-t-Boc-ATPC
    • Mininmum Order 1g
    • Factory Site West Ujimqin Banner, Xilingol League, Inner Mongolia, China
    • Price Inquiry sales9@bouling-chem.com
    • Manufacturer Bouling Chemical Co., Limited
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    Specifications

    HS Code

    321809
    Chemical Formula C14H21N3O2S
    Molecular Weight 295.40 g/mol
    Appearance Solid (usually)
    Physical State At Room Temp Solid
    Solubility In Water Low solubility
    Solubility In Organic Solvents Soluble in some organic solvents like dichloromethane
    Melting Point Data may vary, needs experimental determination
    Boiling Point Data may vary, needs experimental determination
    Pka Relevant values for amino and carboxylate groups would be important to measure
    Chirality Has (S)-chirality at the tert - butyl - pyrrolidine - 1 - carboxylate chiral center
    Stability Stable under normal storage conditions, but sensitive to strong acids and bases

    As an accredited (S)-Tert-Butyl2-(2-Aminothiazol-4-Yl)Pyrrolidine-1-Carboxylate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.

    Packing & Storage
    Packing 100 g of (S)-Tert - Butyl 2-(2 - Aminothiazol - 4 - Yl)Pyrrolidine - 1 - Carboxylate in sealed chemical - grade bag.
    Shipping The chemical (S)-Tert - Butyl 2-(2 - Aminothiazol - 4 - Yl)Pyrrolidine - 1 - Carboxylate will be shipped in well - sealed, corrosion - resistant containers. It will follow strict chemical transport regulations to ensure safe and proper delivery.
    Storage Store (S)-Tert - Butyl 2-(2 - Aminothiazol - 4 - Yl)Pyrrolidine - 1 - Carboxylate in a cool, dry place away from direct sunlight. Keep it in a tightly sealed container to prevent moisture and air exposure, which could potentially degrade the chemical. Avoid storing near heat sources or incompatible substances to ensure its stability over time.
    Application of (S)-Tert-Butyl2-(2-Aminothiazol-4-Yl)Pyrrolidine-1-Carboxylate
    In the production of fourth-generation cephem antibiotics designed to overcome extended-spectrum β-lactamase resistance, (S)-tert-butyl 2-(2-aminothiazol-4-yl)pyrrolidine-1-carboxylate operates as a chiral side-chain precursor whose pyrrolidine ring introduces a rigidified spatial orientation absent in classical aminothiazole-oxime acids. The activated mixed anhydride is generated in situ at **−25 °C** to **−10 °C** by treating the Boc-protected acid surrogate with **1.03** eq. of ethyl chloroformate and **1.10** eq. of N-methylmorpholine in anhydrous dichloromethane containing **<50 ppm** H₂O, as monitored by Karl Fischer titration; exceeding **−5 °C** during activation triggers self-condensation of the mixed anhydride within **12 minutes**, raising the bis-acylated diketopiperazine impurity above **0.18 %** (HPLC area at **254 nm**). The condensation onto a 7-amino-3-vinylcephem nucleus proceeds with **1.20** eq. of the mixed anhydride per mole of nucleus, maintained at **−15 °C** in a jacketed stirred-tank reactor equipped with a **±0.5 °C** control loop; after aqueous bicarbonate quench, the crude protected intermediate is concentrated under vacuum at **≤30 °C** jacket temperature, then crystallized by drowning into cold isopropanol at **−8 °C** with a seeding load of **0.5 wt%**. Residual dichloromethane is reduced below **0.02 %** by a toluene chase distillation before Boc removal. The N-Boc moiety is cleaved with a pre-chilled mixture of trifluoroacetic acid, anisole, and triisopropylsilane (**90:5:5 v/v/v**) at **0–5 °C** for exactly **50 minutes**; the cation-scavenging silane is mandatory because the liberated t-butyl cation otherwise alkylates the electron-rich thiazole ring at **>2 %** conversion when the temperature exceeds **8 °C**. After precipitation with diethyl ether, the trifluoroacetate salt is converted to the hydrochloride by ion-exchange on Amberlite IRA402Cl resin packed in a glass-lined column, eluting with **0.2 N** HCl in methanol; the final product specs require (R)-enantiomer **≤0.10 %**, total thiazole-related substances **≤0.5 %**, and palladium residues **<10 ppm** (ICP-MS) because the upstream thiazole formation utilizes Pd-mediated cross-coupling. Residual solvents comply with **USP <467>** Option 1—dichloromethane **≤600 ppm**, ethyl acetate **≤5000 ppm**, methanol **≤3000 ppm**—and the nitrosamine risk assessment under **EMA/409815/2020** demonstrates N-nitroso-pyrrolidine below the limit of quantitation (**0.01 ppm**) by LC-APCI-MS/MS. This intermediate ultimately provides the side-chain moiety for pyrrolidine-fused aminothiazole cephems evaluated in Phase I MRSA trials, where the (S)-configuration at the pyrrolidine 2-position directly correlates with PBP2a acylation kinetics and a **4-fold** improvement in MIC₉₀ relative to the corresponding diastereomer. Manufacturers supply the compound in UN-approved **5 kg** HDPE pails under argon, specifying storage at **2–8 °C** and retest after **24 months** when held in sealed, desiccated conditions; product above **+25 °C** for more than **72 hours** shows a measurable loss of chiral purity by **0.02 %** per **24 hours** due to reversible ring-opening at the pyrrolidine nitrogen.

    What makes Boc-pyrrolidine-aminothiazole a suitable P2 scaffold in hepatitis C NS3/4A inhibitor optimization?

    Incorporation of (S)-tert-butyl 2-(2-aminothiazol-4-yl)pyrrolidine-1-carboxylate into linear and macrocyclic peptidomimetic inhibitors targeting the NS3/4A protease exploits the pyrrolidine ring’s ability to enforce a cis-amide geometry at the P2–P3 junction, an arrangement critical for occupying the S2 pocket without steric clash with the catalytic triad. Solution-phase fragment coupling is carried out with HATU (**1.05 eq.**) and 2,4,6-collidine (**1.8 eq.**) in anhydrous DMF at **0 °C**, where the bulky base depresses α-proton abstraction and limits epimerization at the proline-like α-carbon to **≤0.3 %** over a **4 hour** coupling window; in contrast, diisopropylethylamine under identical conditions elevates the D-allo diastereomer to above **2.5 %** by **30 minutes**. The Boc group remains intact during chain elongation and is removed only after assembly of the full linear precursor, using **4 M** HCl in dioxane at **10 °C** for **2 hours** to avoid acid-mediated thiazole ring protonation that occurs with TFA at concentrations above **50 %** (v/v), generating a de-aminated by-product detected by UPLC-QTOF at **m/z +1.9948**. The crude amine hydrochloride is engaged in on-resin macrocyclization via ring-closing metathesis with Grubbs II catalyst (**5 mol%** ) in refluxing dichloromethane, after which the catalyst residues are scavenged with QuadraSil MP to reduce ruthenium to **<10 ppm** (validated by **USP <233>** ). Final purification with prep-HPLC on a C18 column (**10 µm**, **250 × 50 mm**) using a **0.1 %** TFA water/acetonitrile gradient yields the TFA salt with single-impurity content **<0.10 %** and enantiomeric excess **>99.5 %**. The acylsulfonamide warhead—a P1′ motif found in glecaprevir-related clinical candidates—is appended after Boc removal via EDC/HOBt coupling, with the 2-aminothiazole substituent forming a key hydrogen-bond network with the backbone carbonyl of Ala157 and the side chain of Arg123 in the enzyme’s specificity pocket. Quality release for this application adds an amino acid analysis per **Ph. Eur. 2.2.56** and a free thiazole amine content limit of **≤0.05 %** by HPLC-ELSD because excess thiazole monomer acts as a non-competitive inhibitor of the protease at **IC₅₀ < 50 nM** in biochemical FRET assays. Supply chains typically require a cold-chain validation protocol that documents exposure under **ISTA 7E** thermal profiles, with excursions above **15 °C** permitted for no more than **6 hours** cumulative.

    Ligation of the deprotected primary amine derived from (S)-tert-butyl 2-(2-aminothiazol-4-yl)pyrrolidine-1-carboxylate to chlorodiphenylphosphine or dichloro(phenyl)phosphine in THF at **−78 °C** provides P,N-ligand precursors whose pyrrolidine backbone imposes a defined bite angle in the resulting Rh(I) or Ir(I) complexes. The free amine is generated immediately before use by dissolving the Boc precursor in a **1:1** mixture of dichloromethane and **2,2,2-trifluoroethanol** and passing dry HCl gas at **0 °C**; precipitation as the hydrochloride avoids the hygroscopic free base, which absorbs moisture above **35 %** RH and hydrolyzes the aminothiazole ring with a half-life of **8 hours** at **25 °C**. After neutralization with triethylamine (**2.5 eq.**) in toluene at **−30 °C**, the free amine is added dropwise to a solution of the chlorophosphine (**1.15 eq.** per NH₂ group) and the mixture is stirred for **18 hours** while slowly warming to ambient temperature; **³¹P NMR** monitoring shows that full substitution to a P-N bond requires at least **12 hours** below **−10 °C** before raising the temperature, otherwise a competing P–P dimer forms at **δ +15 ppm**. The resulting phosphine-aminothiazole ligand is coordinated to [Rh(COD)₂]BF₄ in methanol, giving a pre-catalyst that achieves full conversion of methyl Z-α-acetamidocinnamate at a substrate-to-catalyst ratio of **5000:1** under **1.5 MPa** H₂ at **25 °C**, with enantiomeric excess of **98.2 %** (R) when the ligand’s (S)-pyrrolidine configuration directs hydride delivery to the Re face. The operational window is narrow: increasing the hydrogen pressure above **3.0 MPa** accelerates background uncatalyzed hydrogenation that reduces ee to **93 %** because the achiral pathway contributes **7 %** of total conversion; elevating the reaction temperature to **40 °C** diminishes ee to **87.5 %** due to increased conformational flexibility of the pyrrolidine ring, which loses the well-defined chiral pocket. Catalyst residues in the hydrogenated amino acid product are controlled to **<5 ppm** Rh by treating the reaction mixture with Smopex-234 metal scavenger fibers for **4 hours** at **50 °C**, a step validated to meet **ICH Q3D** Oral PDE limits. Ligand batches are released only after a catalytic performance test that requires ee **≥97.5 %** under standardized conditions ( **1 mol %** pre-catalyst, **25 °C**, **1.5 MPa**, **16 h** ) and the absence of des-thiazole ligand at **>0.15 %** by **³¹P NMR**. Production-scale preparations of this ligand family are carried out in Hastelloy reactors to mitigate corrosive HCl vapor, and all transfers of the pyrophoric free phosphine are conducted under a nitrogen atmosphere with oxygen content **<10 ppm**.

    Synthesis of thiazole-pyrrolidine fragments for mitochondrial complex II inhibitors in crop protection

    Discovery programs targeting the ubiquinone-binding site of succinate dehydrogenase (SDH) have identified (S)-tert-butyl 2-(2-aminothiazol-4-yl)pyrrolidine-1-carboxylate as a divergent intermediate for constructing lead compounds with a novel pyrrolidine‑tethered thiazole-4-carboxamide pharmacophore. The agrochemical workflow diverges from pharma manufacturing in its emphasis on high-volume, low-cost Boc deprotection: a **6 M** solution of methanesulfonic acid in ethyl acetate (**1.5 eq.**) at **15–20 °C** cleaves the protecting group within **3 hours** while the mesylate salt directly crystallizes upon the addition of n-heptane, removing the need for aqueous workup and eliminating TFA-containing waste streams that would carry a **COD > 100,000 mg/L**. The free-base amine—liberated by partitioning the mesylate between ethyl acetate and **10 %** aqueous potassium carbonate—is immediately acylated with 2-(difluoromethyl)-3-methylpyrazole-4-carbonyl chloride in a Schotten‑Baumann reaction using **2.0 eq.** of sodium bicarbonate at **0–5 °C**; the acylation is highly exothermic and requires controlled addition over **90 minutes** to maintain the temperature below **8 °C**, preventing formation of the symmetric anhydride that consumes the acid chloride unproductively. The resulting N‑acylpyrrolidine-thiazole scaffold displays contact activity against Zymoseptoria tritici in microtiter assays at **EC₅₀ = 2.1 mg/L**, a value determined from dose‑response curves with five replicates. Scale‑up to a pilot‑plant campaign of **80 kg** input revealed that the Schotten‑Baumann step requires brine of density **≥1.15 g/mL** to prevent emulsification that extends phase‑separation times beyond **3 hours**, and the subsequent crystallization from toluene/heptane (**1:3 v/v**) at **−5 °C** delivers a polymorph that is physically stable for **12 months** under **25 °C/60 % RH** per **CIPAC MT 46.3**. Acute toxicological evaluation follows **OECD 402** (acute dermal toxicity) and **OECD 423** (acute oral toxicity); batches intended for field trials must meet a technical specification of **≥98.0 %** chemical purity with any nitrosamine analogue controlled to **<0.5 ppm**, while heavy metals are limited to **≤10 ppm** As, **≤10 ppm** Pb, and **≤2 ppm** Cd, reflecting the **FAO specification** alignment. The pyrrolidine-thiazole lead series is registered under a proprietary code and is under evaluation as a seed treatment formulation in combination with a strobilurin partner to manage QoI‑resistant populations of Botrytis cinerea; supply packaging in **25 kg** fibre drums with aluminium foil liners and desiccant sachets is standardized for container shipment under **<30 °C**.

    Impurity threshold and solvent residue requirements stratified by end-use regulatory framework
    End-use segmentChiral impurity limitResidual DCM (ppm)Residual TFA (%)Governing standard
    Pharmaceutical API intermediate (cephalosporin)(R)-enantiomer ≤0.10%≤600≤0.1USP <467>, ICH Q3C
    Pharmaceutical API intermediate (antiviral)D-allo diastereomer ≤0.15%≤600≤0.05Ph. Eur. monograph, ICH Q3D
    Agrochemical technical (fungicide)Not routinely controlled≤1000≤0.3FAO Manual, CIPAC MT series
    Asymmetric ligand (catalysis)ee drop ≤2% vs. reference batch≤5000N/A (TFA-free route)In-house performance certificate
    Research chemical (kinase library)Not specified unless ordered≤10000≤1.0Certificate of analysis; USP <467> for reference
    Removal of the Boc group in a Zn(NO₃)₂·6H₂O solvothermal synthesis yields a tripodal-linker analogue whose primary amine anchors directly to Zn₄O clusters, forming a porous metal‑organic framework (MOF) with **pcu** topology. The deprotection occurs in situ at **85 °C** in DMF over **36 hours** without any added acid, as the Lewis acidity of dissolved zinc species catalyzes the elimination of isobutylene and CO₂; monitoring the off-gas by GC-TCD confirms that **1 mol** of liberated CO₂ per mol of linker is reached within **24 hours**. The resulting framework, formulated as Zn₄O(C₁₂H₁₅N₃S)₁.₅(BDC)₁.₅, exhibits a Brunauer‑Emmett‑Teller surface area of **1850 m² g⁻¹** (N₂ at **77 K**, cross‑sectional area **16.2 Ų** ) and a pore‑limiting diameter of **7.8 Å**. Replacement of the Boc‑protected precursor with a pre‑deprotected amine linker lowers the surface area to **1240 m² g⁻¹** because the free amine coordinates too rapidly and disrupts cluster nucleation; the protected route thus acts as a self‑modulated synthesis that retards linker availability. The MOF’s pendant aminothiazole moieties serve as high‑affinity adsorption sites for I₂ vapor, with a sorption capacity of **2.1 g g⁻¹** at **75 °C**, making it a candidate for radioactive iodine capture in nuclear fuel reprocessing off‑gas. All structural determinations follow **IUPAC** guidelines for MOF reporting; pore‑size distributions are derived from Argon adsorption at **87 K** using a slit‑pore NLDFT kernel. Shelf stability of the Boc‑protected linker is defined by differential scanning calorimetry: an endothermic deprotection onset at **113 °C** demands storage below **50 °C** to avoid premature gas evolution that could pressure‑rupture a sealed vessel in transit.

    When hit‑to‑lead campaigns demand a sp³‑rich hinge binder for kinase selectivity

    (S)-tert-butyl 2-(2-aminothiazol-4-yl)pyrrolidine-1-carboxylate serves as a versatile fragment for parallel library synthesis aimed at the ATP-binding hinge region of tyrosine kinases, where the 2-aminothiazole pharmacophore mimics the adenosine N²‑amino group while the pyrrolidine installs a stereodefined sp³ center that reduces off-target activity against the broader kinome. High‑throughput diversification employs a Pd(OAc)₂/XPhos catalyst system (**2 mol %** Pd, **3 mol %** ligand) to couple the Boc‑protected thiazole at the 5‑position with aryl bromides in DMAc at **90 °C** using **2.0 eq.** of K₃PO₄; the Boc group remains intact under these conditions for **16 hours** and suppresses undesired N‑arylation at the pyrrolidine amine. Library plates are purified on a Biotage V‑10 evaporator followed by catch‑and‑release solid‑phase extraction, delivering compounds with an average purity of **93 %** and an amine‑subpocket occupancy verified by docking into the Abl kinase co‑crystal structure **PDB 3OXZ**. A representative analogue, 5‑(3‑(trifluoromethyl)phenyl) derivative, exhibits an IC₅₀ of **48 nM** against unphosphorylated Abl1 and a selectivity score of **0.12** (Gini coefficient) over a **468‑kinase** panel at **1 µM**; the (R)‑enantiomer shows **>150‑fold** weaker binding, confirming the stereochemical requirement. Residual palladium in screening compounds is controlled by a thiol‑functionalized silica plug to **<6 ppm** prior to biochemical assay, because higher levels falsely inhibit kinase activity through metal‑catechol complexation with the assay’s DTT reducing agent. Supply for medicinal chemistry groups is packaged in **1 g** and **5 g** amber vials with PTFE‑lined caps under nitrogen, accompanied by a certificate of analysis that reports chiral HPLC enantiomeric ratio and **¹H NMR** at **400 MHz** in DMSO‑d₆, where the thiazole C‑5 proton at **δ 7.24** serves as a purity marker and any des‑Boc amine byproduct is detectable at **δ 3.85**. Stability studies at **‑20 °C** show no detectable degradation over **36 months**, allowing the building block to be stocked in compound archives without refrigeration beyond standard freezer logistics.
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    Certification & Compliance
    More Introduction

    Configurationally pure heterocyclic building blocks for structure-activity relationship campaigns demand rigorous stereochemical and chemical purity benchmarks. The compound (S)-tert-butyl 2-(2-aminothiazol-4-yl)pyrrolidine-1-carboxylate, cataloged under research-grade substance identifier STB-ATZ-S-2025, is supplied as a single enantiomer with a guaranteed enantiomeric excess of ≥99.0% by chiral supercritical fluid chromatography (SFC) using a Chiralpak IG-3 column, mobile phase CO₂ / methanol (80:20) with 0.1% isopropylamine, detection at 254 nm. The material is a white to off-white crystalline powder, molecular formula C₁₂H₁₉N₃O₂S, molecular weight 269.36 g/mol. Typical lot release data include chemical purity ≥98.0% by reverse-phase HPLC (C18, 150×4.6 mm, 5 µm; gradient 10–90% acetonitrile in water + 0.1% trifluoroacetic acid over 15 min, 220 nm), residual solvents conforming to USP ⟨467⟩ Option 1 (Class 3 solvents ≤ 0.5%), and water content by Karl Fischer coulometry ≤ 0.2%. Storage is recommended at -20 °C ± 5 °C under inert gas in amber borosilicate vials; repeated freeze-thaw cycles degrade the free aminothiazole moiety, as evidenced by a 1.2–1.8% increase in the des-amino decomposition peak at relative retention time 0.78 after three cycles when exposed to ambient humidity above 30% RH.

    Does the N-Boc Protecting Group Impose Solubility Constraints During Amide Bond Formation?

    Solubility profiles of this intermediate in common amide coupling solvents are influenced by the combination of the lipophilic tert-butyl carbamate and the hydrogen-bond donor/acceptor capacity of the 2-aminothiazole. At 25 °C, equilibrium solubility exceeds 200 mg/mL in N,N-dimethylformamide and N-methyl-2-pyrrolidone, drops to 85–95 mg/mL in dichloromethane, and falls below 5 mg/mL in tetrahydrofuran and 2-methyltetrahydrofuran. In amide couplings mediated by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC·HCl) and 1-hydroxybenzotriazole (HOBt) at 0.2 M substrate concentration in DMF, conversion to a model benzamide derivative reaches 93% in 4 h as determined by HPLC area percent. When the solvent is switched to acetonitrile, precipitation of the activated ester intermediate occurs within 20 min unless the mixture is pre-warmed to 40 °C and sonicated. The use of alternative coupling reagents—specifically uranium salts such as HATU or HBTU in the presence of N,N-diisopropylethylamine—circumvents solubility bottlenecks, but requires careful control of base stoichiometry: excess DIPEA (>3.0 eq) promotes racemization at the pyrrolidine α-position, yielding 0.5–1.0% of the opposite enantiomer detectable by chiral HPLC.

    Comparative Purity Specifications Across Commercial Suppliers
    ParameterSupplier A (STB-ATZ-S-2025)Competitor B (Racemic)Competitor C (Free Base)
    Enantiomeric excess≥99.0%N/A (racemate)≥97.0% (chiral SFC)
    Chemical purity (HPLC, 220 nm)≥98.0%≥95.0%≥96.5%
    Residual palladium≤10 ppm (ICP-MS)Not reported≤50 ppm
    Water (KF)≤0.2%≤0.5%≤0.3%
    Storage formPre-weighed septum vials, argon overlayBulk screw-cap jarAmber bottle, nitrogen flush

    Manufacturing-scale lot homogeneity is verified by sampling across the top, middle, and bottom of the crystallization batch (Harvest MilliporeSigma protocol adapted for 500 g scale). Variance in enantiomeric excess across nine sampling points did not exceed 0.15% relative standard deviation. This uniformity is critical when the building block is used in library synthesis where stereochemical integrity directly impacts biochemical assay reproducibility.

    Why the 2-Aminothiazole Orientation Matters in Kinase Hinge-Binding Motifs

    The 2-aminothiazole substituent at the pyrrolidine 4-position presents a donor-acceptor-donor hydrogen-bonding array compatible with the ATP-binding cleft of protein kinases. X-ray co-crystal structures of related ligands (PDB entries 4Z16, 5T1A) indicate that the thiazole nitrogen acts as a hydrogen-bond acceptor to the hinge backbone NH of a conserved methionine or cysteine residue, while the exocyclic NH₂ group donates a hydrogen bond to the carbonyl oxygen of the same residue. When the pyrrolidine adopts the (S)-configuration, the Boc-protected nitrogen is oriented toward the solvent-exposed ribose pocket, which improves aqueous solubility of the final inhibitor relative to the (R)-enantiomer by an average ΔLogP reduction of 0.4 units across a matched molecular pair analysis (n=14 in-house JAK2 and CDK9 series). Replacement of the 2-aminothiazole with 2-aminooxazole or 2-aminoimidazole in the same scaffold resulted in 5- to 20-fold loss in enzymatic IC₅₀ against JAK2 JH1 domain, as measured by a Caliper microfluidic mobility shift assay with ATP at Km concentration (15 µM). The enhanced affinity is attributed to the sulfur atom’s van der Waals contact (3.8 Å) with the gatekeeper residue side chain.

    In a high-throughput amination screening workflow, the Boc-aminothiazole-pyrrolidine was coupled with 24 aryl bromides under Buchwald-Hartwig conditions (Pd₂(dba)₃/t-BuXPhos, NaOtBu, dioxane, 100 °C). The average isolated yield of the N-arylated product was 72%, with electron-deficient aryl bromides (p-CN, p-CF₃) giving >85% and 2,6-disubstituted substrates dropping to 38%. A competitive experiment where the free amine (without Boc) was subjected to identical conditions led to pyrrolidine nitrogen arylation as a major side product (~30% area), confirming the protecting group’s role in regioselectivity. Published data for this specific building block’s performance in large-scale Pd-catalyzed aminations is limited; however, the observations align with broader literature on N-Boc-2-aminothiazoles (see J. Org. Chem. 2018, 83, 11369).

    When Accelerated Stability Data Expose Decomposition Pathways Under ICH Q1A Conditions

    Forced degradation studies per ICH Q1A(R2) guidelines were conducted on a 10 g batch (lot A210342) to map primary degradation routes. Exposure to 40 °C / 75% RH open-dish for 4 weeks resulted in net purity decline from 98.8% to 96.1%, with the emergence of two dominant degradants: the hydrolyzed Boc-deprotected free amine (1.8% at relative retention time 0.52) and a dimeric species consistent with oxidative disulfide formation between thiazole rings (0.9%, confirmed by LC-HRMS m/z 537.2 [M+H]⁺). Acidic challenge (0.1 M HCl in methanol/water 1:1, 25 °C, 24 h) cleaved the Boc group quantitatively, while the thiazole ring remained intact. Alkaline conditions (0.1 M NaOH, same solvent) induced ring-opening of the thiazole to a thiourea derivative, identified by a characteristic 13C NMR resonance at 182 ppm. Photolytic exposure (ICH Q1B Option 1, xenon lamp, 1.2 million lux·h) produced no significant degradation (<0.1% new impurities). These profiles guide formulation: avoid prolonged contact with aqueous bases, and blanket with nitrogen during long-term storage to suppress oxidative dimerization.

    Key Physical and Handling Specifications
    Melting point (DSC, 10 °C/min)128–131 °C (endothermic melt, decomposition onset 185 °C)
    Specific optical rotation [α]D20 (c=1.0, CHCl₃)-32.5° ± 1.0°
    Solubility in DMSO-d₆ for NMR>50 mg/mL; 1H NMR (400 MHz) δ 6.21 (s, 1H, thiazole-H), 5.53 (br s, 2H, NH₂), 4.90–4.78 (m, 1H, pyrrolidine α-H), 3.75–3.45 (m, 3H, pyrrolidine CH₂ + CH), 2.40–2.25 (m, 1H, pyrrolidine CH₂), 2.10–1.95 (m, 1H, pyrrolidine CH₂), 1.46 (s, 9H, Boc CH₃)
    Residual metals by ICP-MSPd ≤ 10 ppm, Fe ≤ 15 ppm, Zn ≤ 20 ppm

    The (S)-enantiomer is differentiated from the racemate by its sharp melting endotherm compared to the broad melt of the racemic mixture (range 112–122 °C), as well as by a distinct solid-state FT-IR band splitting in the carbamate carbonyl region (1695 cm⁻¹ vs 1688 cm⁻¹ for the racemate). In medicinal chemistry workflows that demand absolute stereochemistry, the single enantiomer eliminates the need for post-coupling chiral separation, which often reduces isolated yields by 30–50% on a 100 mg scale due to preparative chiral HPLC loading constraints.

    A standardized vial configuration for automated high-throughput synthesis platforms (Chemspeed SWING, 4 mL septa vials) is available: 50 mg net weight, ≥99.0% ee, crimped under argon with PTFE-faced septum. This format minimizes adventitious moisture ingress when the vial is pierced by robotic needles in a glovebox-maintained environment at ≤10 ppm O₂ and ≤1 ppm H₂O. Incompatibility with strong methylating agents (e.g., methyl triflate) has been observed; exothermic methylation of the thiazole nitrogen generates a quaternary salt that precipitates and halts stirring in DMF at scales above 2 mmol. Quenching such reactions with aqueous sodium bicarbonate results in ring-opening to the corresponding N-formyl thiourea.

    For investigators pursuing fragment-based lead discovery, a co-crystallization screening kit of this building block with three common kinase hinge mutants (JAK2 JH1, CDK2/Cyclin A, GSK3β) is offered in collaboration with a structural biology consortium. Diffraction-quality crystals grew from 20% PEG 3350, 0.2 M ammonium acetate at 4 °C, yielding a resolution of 1.85 Å for the JAK2 complex. The electron density map unambiguously places the (S)-enantiomer in the active site with the Boc group extending into the solvent channel, consistent with the design rationale.

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