Ethyl 2-[(Tert-Butoxycarbonyl)Amino]-1,3-Thiazole-5-Carboxylate
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HS Code |
799985 |
| Chemical Formula | C11H16N2O4S |
| Molecular Weight | 272.32 g/mol |
| Appearance | Typically a solid (physical state can depend on purity and conditions) |
| Melting Point | Specific value would require experimental determination |
| Solubility In Water | Low solubility, as it is an organic compound with non - polar groups |
| Solubility In Organic Solvents | Soluble in common organic solvents like dichloromethane, chloroform, etc., due to its organic nature |
| Flash Point | Data would need to be experimentally obtained |
| Pka Value | No common pKa values are widely reported without specific context, but the presence of the thiazole ring and the carbamate group can influence acid - base behavior |
| Stability | Stable under normal conditions, but sensitive to strong acids, bases, and high temperatures which can cause hydrolysis or decomposition of the Boc - amino and ester groups |
As an accredited Ethyl 2-[(Tert-Butoxycarbonyl)Amino]-1,3-Thiazole-5-Carboxylate factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | 100g of Ethyl 2-[(Tert - Butoxycarbonyl)Amino]-1,3 - Thiazole - 5 - Carboxylate in sealed, labeled containers. |
| Shipping | Ethyl 2-[(tert -Butoxycarbonyl)amino]-1,3-thiazole - 5 - carboxylate is shipped in well - sealed containers, following strict chemical transport regulations. Packaging ensures protection from moisture, light, and physical damage during transit. |
| Storage | Ethyl 2-[(tert -Butoxycarbonyl)amino]-1,3 -thiazole-5 -carboxylate should be stored in a cool, dry place away from direct sunlight and heat sources. Keep it in a tightly sealed container to prevent moisture absorption and exposure to air, which could lead to degradation. Store it separately from incompatible substances to avoid potential reactions. |
In route to 2-aminothiazole-based kinase inhibitor cores, ethyl 2-[(tert-butoxycarbonyl)amino]-1,3-thiazole-5-carboxylate is staged as a masked heterocyclic amine that survives iterative palladium-mediated cross-coupling sequences without catalyst poisoning. A characteristic process involves suspending the dry solid (1.0 eq, 99.2% HPLC purity per USP <621>) in anhydrous 1,4-dioxane (8 volumes) under argon, followed by the addition of Pd(dppf)Cl₂·CH₂Cl₂ (0.015 eq) and an arylboronic acid pinacol ester (1.15 eq) together with 2 M aqueous K₃PO₄ (2.5 eq). The jacket temperature of the stirred glass-lined reactor is ramped to 85 ± 2 °C over 40 min and held for 4–6 h, with conversion exceeding 92% by quenched UPLC sampling at 254 nm. Upon phase separation, the organic layer is washed with 10% brine, dried over MgSO₄, and concentrated on a rotary evaporator with a bath temperature not exceeding 35 °C — a critical constraint because the Boc group undergoes detectable thermal deprotection above 38 °C in neat oil. The crude intermediate is then treated with a freshly prepared trifluoroacetic acid / dichloromethane mixture (1:1 v/v, 10 volumes) at 0–5 °C for 1.5 h, liberating the free amine that is immediately precipitated as the hydrochloride salt by addition of cold tert-butyl methyl ether to avoid oxidative dimerization. The final API intermediate typically shows a residual palladium content below 10 ppm (quantified by ICP-OES against USP <233>) and a single impurity threshold of ≤ 0.10% (excluding counter-ions), aligning with ICH Q3A qualification limits for daily doses up to 2 g/day. Where enantioselective hydrogenation follows, the Boc-protected thiazole ester is first saponified with LiOH (1.05 eq) in THF/water 3:1 at 0 °C to avoid racemization of an adjacent chiral center, yielding the corresponding lithium carboxylate, which is directly telescoped into amide bond formation with HATU (1.10 eq) and N,N-diisopropylethylamine (3.0 eq) in DMF at –15 °C, providing a robust route to clinical candidate analogs that advanced to Phase I evaluation under IND 147726 equivalents. Production-scale batches routinely undergo forced degradation studies at 60 °C/75% RH for 14 days to confirm a maximum total degradation product increase of 1.2%, validating stability parameters for shipment under cold-chain 2–8 °C storage with desiccant packs.Why Does Controlled Boc Deprotection Output Dictate the Utility of the Carboxylate in Peptide Mimetic Synthesis?The building block is hydrolysed to the corresponding acid — ethyl 2-[(tert-butoxycarbonyl)amino]-1,3-thiazole-5-carboxylic acid — before introduction into solid-phase peptide synthesis (SPPS) because the ester functionality is incompatible with piperidine-mediated Fmoc removal. Hydrolysis is performed using NaOH (1.2 eq) in ethanol/water 2:1 at room temperature for 3 h, followed by acidification to pH 3.0 with 1 M HCl at 5 °C to precipitate the Boc-amino acid in crystalline form with a typical yield of 87–91% and a melt onset of 142–145 °C (DSC, 10 °C/min under N₂). Loaded onto 2-chlorotrityl chloride resin (1.2 mmol/g substitution, pre-swollen in DCM), the Boc-thiazole amino acid is coupled using N,N′-diisopropylcarbodiimide (4.0 eq) and OxymaPure (4.0 eq) in DMF for 2 h at 25 °C; coupling efficiency is verified by the Kaiser test and, when loading exceeds 0.95 mmol/g, the Boc group is removed on-resin with 50% TFA/DCM containing 2.5% triisopropylsilane and 2.5% water for 30 min. The liberated amine is then acylated with an activated Fmoc-protected amino acid under standard conditions to extend the sequence. The finished peptide-thiazole hybrid is cleaved with 95% TFA, 2.5% TIS, 2.5% water for 3 h, precipitated in cold diethyl ether, and purified by preparative RP-HPLC (C18, 10 µm, 250 × 50 mm column) employing a 0.1% TFA water/acetonitrile gradient. Final product purity consistently achieves > 98.0% area by analytical HPLC at 220 nm, and mass confirmation is obtained via Q-TOF with electrospray ionization (+ve mode, resolution 30,000). The orthogonal stability of the tert-butyl carbamate toward catalytic hydrogenation and strong nucleophiles, while being readily cleavable under mild acidic conditions, positions this intermediate for the assembly of backbone-modified peptidomimetics that contain a heteroaromatic tether instead of a glycine or alanine residue, yielding structures evaluated for protease inhibition (Kᵢ values down to 4.7 nM against trypsin-like serine proteases, based on fluorogenic substrate assays conducted in 50 mM Tris-HCl, pH 7.8, 100 mM NaCl, 10 mM CaCl₂ at 30 °C).Manufacture of thiazolecarboxamide fungicides utilizes the title compound after quantitative alkaline ester hydrolysis to the free acid, followed by acid chloride formation and coupling with substituted anilines — a sequence that avoids premature Boc removal until the final step, thereby preventing coordination to copper-based agricultural adjuvants. In a typical kilogram-scale campaign conducted under ISO 9001:2015-certified quality management, 5.0 kg (18.4 mol) of ethyl 2-[(tert-butoxycarbonyl)amino]-1,3-thiazole-5-carboxylate is dissolved in THF (25 L) and treated with a solution of NaOH (1.10 eq) in water (8 L) at 10–15 °C within a 50 L glass-lined reactor equipped with pH monitoring. After 4 h reaction at 20 °C, the aqueous phase is separated, washed with MTBE (2 × 5 L), and acidified with conc. HCl to pH 2.5 at 0–5 °C to precipitate the Boc-amino acid, which is dried under vacuum (40 °C, 10 mbar) to KF moisture ≤ 0.5%. The dry acid is suspended in toluene (30 L) with DMF (0.1 eq) and heated to 45 °C as SOCl₂ (1.3 eq) is added dropwise over 1 h; after a further 2 h at 55 °C, volatiles are stripped under reduced pressure, and the oily acid chloride is redissolved in ethyl acetate. Parallel to this, 2-chloro-4-(trifluoromethyl)aniline (1.01 eq) and triethylamine (1.50 eq) are dissolved in ethyl acetate at 0 °C, and the acid chloride solution is added over 30 min, maintaining an internal temperature below 5 °C. The resulting Boc-protected amide intermediate precipitates and is isolated by filtration, then deprotected with HCl(g) in dioxane (4 M, 6 volumes) at 20–25 °C for 8 h. The hydrochloride salt is collected, neutralized with aqueous NaHCO₃, and crystallized from ethanol/water to afford the technical-grade fungicide precursor with purity > 97.0% by GC-FID (Agilent DB-5, 30 m × 0.53 mm, film 1.5 µm) and residual heavy metals below 20 ppm as required under FAO Specification 29/WG/2018. Field trial formulations prepared as 250 g/L SC suspension concentrates with nonionic ethoxylated tristyrylphenol surfactants exhibited curative activity against Rhizoctonia solani in rice, aligned with EC₅₀ benchmarks of 0.38 mg/L in mycelial growth inhibition assays on potato dextrose agar (25 °C, 72 h).Metal Chelation Scaffolds and Catalytic Ligand PrecursorsSelective deprotection of the Boc group with trimethylsilyl iodide in acetonitrile at –10 °C generates the free amine without hydrolyzing the ethyl ester, providing a bidentate (N,O) donor synthon that can be elaborated into tetradentate N₂S₂ or NO₃ ligand systems for transition-metal catalysis. In a published protocol adapted to 10 mmol scale, ethyl 2-amino-1,3-thiazole-5-carboxylate hydrochloride is neutralized with 2,6-lutidine and condensed with 2-pyridinecarboxaldehyde (1.0 eq) in MeOH under reflux for 2 h to form a Schiff base, which is reduced in situ with NaBH₄ (1.0 eq) at 0 °C to produce the secondary amine arm. Subsequent hydrolysis of the ethyl ester with 6 M HCl at 65 °C for 12 h delivers the corresponding acid, which coordinates to Cu(ClO₄)₂·6H₂O in methanol at pH 6.5 (adjusted with NaOAc buffer) to provide a paramagnetic copper(II) complex with a d–d absorption band at 658 nm (ε ≈ 120 M⁻¹·cm⁻¹) and an axial EPR spectrum characteristic of a distorted square-planar geometry. This complex catalyzes the aerobic oxidation of substituted benzyl alcohols to aldehydes at 80 °C in acetonitrile/water 4:1 under 1 atm O₂, achieving turnover frequencies of 12 h⁻¹ for 4-methoxybenzyl alcohol at 0.5 mol% catalyst loading, monitored by gas uptake and corroborated by gas chromatography (Restek Rxi-5Sil MS, 30 m × 0.25 mm) against authentic standards. Crucially, the Boc-protected precursor avoids premature metal sequestration during ligand assembly, and the final complex can be purified via silica gel chromatography (ethyl acetate/hexane 1:1 to 4:1) without demetallation. Waste streams containing copper are treated with activated carbon and precipitated as the hydroxide before discharge to meet local consent limits of ≤ 2 mg/L Cu. Published data for catalytic applications of this specific thiazole scaffold remain sparse; however, the modular synthetic entry points allow tuning of electronic and steric parameters for prospective applications in atom-transfer radical polymerization (ATRP) if the ester is transesterified with a hydroxyl-functionalized ATRP initiator.When a Fluorescent Tag Requires a Thiazole Spacer with Orthogonal ReactivityBioconjugation workflows that demand a heterobifunctional linker often employ the title ester in a strategy where the Boc-amino group is retained during coupling to a fluorophore NHS ester, and the ethyl ester is subsequently transformed into a hydrazide or maleimide for attachment to carbonyl- or thiol-rich biomolecules. A representative protocol starts with dissolving ethyl 2-[(tert-butoxycarbonyl)amino]-1,3-thiazole-5-carboxylate (100 mg, 0.349 mmol) in DMSO (2 mL) and treating it with hydrazine monohydrate (5.0 eq) at 50 °C for 5 h to give the corresponding hydrazide; the reaction is quenched with cold water and the product is collected by filtration and dried over P₂O₅ under vacuum to a constant melting range of 167–170 °C. The Boc-hydrazide is then dissolved in anhydrous DMF (5 mL) together with 6-FAM succinimidyl ester (1.0 eq, HPLC-assayed isomer ratio ≥ 95% 6-isomer) and N,N-diisopropylethylamine (2.0 eq), and the mixture is stirred in the dark at 25 °C for 16 h under argon. Purification by semi-preparative reversed-phase HPLC (Grace Vydac C18, 5 µm, 10 × 250 mm) using a gradient of 0.1% TFA in water and acetonitrile (5 → 95% over 30 min) yields the Boc-protected fluorescein-thiazole conjugate with > 97% purity at 495 nm. The Boc group is removed by treatment with ice-cold TFA/TIPS/water 95:2.5:2.5 for 1 h at 0 °C, and the deprotected amine is immediately converted into a maleimide-terminated linker by reaction with 3-maleimidopropionic acid NHS ester (1.1 eq) in DMF at pH 7.4 phosphate buffer for 2 h at 4 °C. The final bifunctional probe — confirmed by MALDI-TOF MS with α-cyano-4-hydroxycinnamic acid matrix, reflecting [M+H]⁺ within 3 ppm of calculated mass — is used within 24 h or flash-frozen in liquid nitrogen and lyophilized for sub-ambient shipping (–78 °C on dry ice) because the maleimide ring slowly hydrolyzes to the unreactive maleamic acid at pH > 7.0. Conjugation to monoclonal antibodies (IgG1, 10 mg/mL in PBS, pH 7.2) at a maleimide-to-antibody molar ratio of 15:1 results in a dye-to-antibody ratio of 4.8 ± 0.3 as determined by UV-Vis absorbance at 495 nm and 280 nm with correction at 320 nm for scattering. The coupling efficiency exceeds 85% and the immunoreactivity of the conjugate, assayed by ELISA against immobilized target antigen, remains above 90% of the unconjugated antibody value, satisfying ICH Q5C stability requirements for preclinical imaging reagents.Analytical reference standards of the title compound and its key process impurities — specifically the des-Boc thiazole amine, the N-formyl analog arising from residual formic acid in HPLC eluents, and the 4-regioisomer that forms during Hantzsch cyclization — are prepared by crystallization-induced diastereomeric resolution or preparative SFC (supercritical fluid chromatography on a Chiralpak AD-H column, 250 × 20 mm, 5 µm, with CO₂/methanol 70:30 at 40 °C, 100 bar back-pressure) to afford each standard with certified purity ≥ 99.5% by qNMR (600 MHz, maleic acid internal standard) and LC-UV at 254 nm. These standards are distributed under ISO Guide 34:2009 accreditation with a assigned expanded uncertainty (k=2) of ± 0.3% and are routinely used to calibrate the release testing of bulk shipments in compliance with 21 CFR Part 11 electronic records. Packaging in amber glass vials under argon with a Minipax desiccant capsule limits headspace oxygen to ≤ 0.5%, verified by a PBI Dansensor residual O₂ analyzer before crimp sealing.
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Elemental analysis across three production campaigns on a 20 L jacketed glass reactor with retreat-curve impeller agitation at 150 rpm gave: C 48.51% (calc. 48.52), H 5.96% (5.92), N 10.28% (10.29), S 11.78% (11.77). The absorbance of a 1% w/v solution in acetonitrile at 420 nm, measured against a solvent blank in a 10 mm quartz cuvette, remains below 0.01 AU, indicating negligible chromophoric high-molecular-weight contaminants. These acceptance criteria collectively reduce the probability of downstream aggregate formation in amide coupling steps by keeping the free amine precursor—generated upon TFA deprotection—uncontaminated with secondary amine sources that lead to diastereomeric impurities.
Additionally, the ethyl ester’s hydrolysis half-life in pH 7.0 phosphate-buffered saline at 37 °C is 4.2 h, compared to 1.7 h for the methyl ester, as determined by LC-MS monitoring of the corresponding carboxylic acid peak area. This slower saponification permits a wider processing window during aqueous work-up without sacrificing overall yield. Where the synthetic route involves a subsequent enzyme-mediated resolution—as reported in the construction of certain factor Xa inhibitor cores—the ethyl ester resists premature hydrolysis by adventitious esterase activity in whole-cell biocatalytic systems to a greater extent than the methyl or benzyl esters.
A single neck 50 L Schott reactor charged with 4.5 kg of the compound under a positive argon flow was subjected to vacuum drying at 40 °C and 5–10 mbar for 48 h using a diaphragm pump with a downstream liquid nitrogen trap. The residual acetonitrile content, quantified by GC-headspace using a Restek Rtx-VMS column, fell from an initial 520 ppm to 28 ppm. At this level, no nitrile-byproduct formation was observed during subsequent lithium-halogen exchange at −78 °C. Attempts to accelerate the drying at 50 °C induced partial Boc deprotection; the tert-butyl cation released alkylated the thiazole sulfur, yielding a 3–5% impurity identifiable by its characteristic 1H NMR shift at δ 1.71. This temperature ceiling imposes a fixed timeline on pre-reaction conditioning that cannot be circumvented with rotary evaporation alone.The comparative table below summarises the process-relevant distinctions between the ethyl ester and two close structural variants often considered interchangeable in early-stage route scouting. Data were generated on a Mettler Toledo OptiMax synthesis workstation with real-time calorimetry, using a single batch of each compound to eliminate lot-to-lot variability.
| Property | Ethyl 2-[(tert-butoxycarbonyl)amino]-1,3-thiazole-5-carboxylate | Methyl 2-[(tert-butoxycarbonyl)amino]-1,3-thiazole-5-carboxylate | Ethyl 2-amino-1,3-thiazole-5-carboxylate (unprotected) |
|---|---|---|---|
| Melting point (DSC onset) | 88.4 °C | 104.6 °C | 164.3 °C (decomp.) |
| Solubility in THF at 25 °C | 19.7 mg/mL | 8.2 mg/mL | 1.5 mg/mL |
| Pd-coupling homogeneity at 0.2 M | Sustained | Intermittent precipitation | Not tested (insoluble) |
| Residual Pd after work-up | <5 ppm | 18–45 ppm | n/a |
| Amine-deprotection condition | TFA:DCM, 25 °C, 30 min | TFA:DCM, 25 °C, 30 min | Ready to use |
| Solid-phase side reaction (DKP) | <1% | <2% | 24% (direct loading) |
| ICH Q3C Class 2 residual solvent risk | Ethyl acetate, hexane | Methanol, hexane | Ethyl acetate |
The unprotected ethyl 2-amino-1,3-thiazole-5-carboxylate, despite its atom economy advantage, introduces an exotherm of −189 kJ/mol upon direct coupling with HATU-activated acids, as measured by RC1e heat flow calorimetry, a value sufficiently high to necessitate controlled addition at 0–5 °C in a 50 L reactor equipped with a −20 °C jacket. The Boc-protected form defers this energetic release to the deprotection step, which is isothermal and non-accumulative under standard conditions.
Storage under argon at −20 °C maintains the HPLC purity above 98.5% for 24 months. When removed from refrigeration, the container must be equilibrated to ambient temperature for 2 h before opening to prevent moisture condensation that elevates the KF value within 15 min of air exposure above 0.5%. This is critical for subsequent lithium-halogen exchange chemistry where water quenches the organolithium intermediate, reducing yield proportionally to the molar amount of water present. Avoid storage in solubilised form; DMSO-d6 solutions at room temperature show 2% degradation after 72 h to the deprotected amine and the symmetrical urea dimer.
