Organic Process Research & Development最新文献

A novel synthetic route was developed to synthesize 6-keto estradiol (2), an intermediate in the synthesis of fulvestrant and analogues. Using norandrostenedione as a starting material, the target 2 was obtained through five step reactions including esterification, hydroxylation, oxidation, enzyme-catalyzed dehydrogenative aromatization, and enzyme-catalyzed reduction. In hydroxylation, phthalic anhydride (PA)/H₂O₂/pyridine was developed as a catalytic system to give the desired 6a and 6b in 90% yield under mild conditions. The enzyme 3-ketosteroid-Δ¹-dehydrogenase (Δ¹-KstD) was utilized for the dehydrogenative aromatization of the A ring in 7, while 17β-hydroxysteroid dehydrogenases (17β-HSDs) were employed for the stereoselective reduction of 17-keto in 8. The related impurities and process parameters were studied in detail. In addition, the scale-up of this synthetic route was successfully executed on a 300.00 g scale, yielding 159.04 g of 6-keto estradiol (2) with a purity of 99.6% and an overall yield of 50% in five steps. Other notable features of this synthetic route included high yields, mild reaction conditions, and inexpensive and commercially available starting materials.

Representative oligonucleotides (oligos), a 21-mer siRNA strand and a 16-mer ASO-like gapmer, were synthesized by Nanostar Sieving, a membrane-assisted liquid phase oligo synthesis (LPOS) method, at a 10 mmol scale and 20 mM concentration in a single solvent. This process is the first total LPOS beyond 10-mer, i.e., the reagents and intermediates remain in the liquid phase from the very first reaction to isolation. At all times during the synthesis of the full-length product, the concentration of oligos within the Nanostar-10 reactor remained roughly constant. Both sequences were synthesized four times, twice using membrane sheets clamped flat in circular cells and twice using scalable spiral wound modules. Cleavage and deprotection continued to maintain the oligo in the liquid phase until the final lyophilization, when yields were calculated from the optical density, adjusting for chromatographic and mass spectral purity. Synthetic process mass intensities approaching those of solid phase oligo synthesis (SPOS) were achieved.

Six nucleophilic aromatic substitution (S_NAr) reactions were efficiently scaled to 10–20 g batch sizes in water without the use of organic solvents or surfactants. Each reaction reached completion within 6 h through simple heating above the melting points of the reactants. The workup involved filtration with pure water, eliminating the need for organic extraction. This streamlined, solvent- and surfactant-free protocol consistently delivered high-purity crystalline products in excellent yield, offering a significantly more sustainable alternative to traditional S_NAr methods that rely on polar aprotic solvents or aqueous surfactant additives.

Attenuated total reflection Fourier transform infrared (ATR-FTIR) is a widely used process analysis technique (PAT) in industrial crystallization, which is generally considered to have no response to solids during crystallization. This work, however, discovered an under-reported distortion in ATR-FTIR spectra during the crystallization of L-carnitine (LC). The observed distorted infrared (IR) spectra appear to exhibit an unexpected blue shift and a large intensity increase of the dissolved L-carnitine (LC) characteristic peak at 1595 cm^–1. PXRD validation and probe-wiping experiments attributed such distortion to partial fouling on the probe surface. Traditional spectral quantification based on the external standard method was found to fail when it was applied to distorted IR spectra. To address the quantification challenge, machine learning (ML) models were evaluated for quantifying the solution concentration under fouling conditions. The results revealed that ML approaches, specifically support vector regression (SVR) and shallow neural network (SNN), achieved accurate quantitative analysis of the LC solution concentration. This work not only improves the understanding of ATR-FTIR spectral distortion but also highlights the potential application of ML-integrated PAT in crystallization process monitoring.

Here, we report on the contribution of structural analysis by microcrystal electron diffraction (3D ED/MicroED) to risk assessment of nitrosamine drug substance-related impurities (NDSRIs). Our study mainly consists of three parts. First, we conducted a basic scope and limitations study on the structure analysis of various nitrosamines and natural nitrosamine products by 3D ED/MicroED. There have been no reports on the feasibility of 3D ED/MicroED analysis of various nitroso compounds to date, and our research has demonstrated that it is possible to determine their molecular structures without any problems. Next, we carried out a 3D ED/MicroED structural analysis of a syn/anti mixture of N-nitrosamines derived from asymmetric secondary amines. N-nitrosovonoprazan was used as a target, and a crystal of the syn/anti mixture could be analyzed as a disordered structure. Finally, we investigated the structural analysis of N-nitroso compounds obtained by direct N-nitrosation of compounds containing two or more secondary amine moieties. Two N-nitroso compounds obtained from the direct nitrosation of palbociclib were analyzed. As a result, the structures of both products were successfully determined easily, including the minor component for which the position of nitroso introduction could not be determined by NMR alone.

A series of ruthenium complexes, mainly Grubbs- and Hoveyda–Grubbs-type catalysts, along with a variety of σ-donor additives, were employed in dehydrogenative alcohol coupling (DAC) reactions to selectively convert primary aliphatic alcohols into carboxylic acids and Guerbet alcohols. Additives such as pyridine or tricyclohexylphosphine served as stabilizing ligands, improving catalyst integrity and thereby boosting selectivity and overall activity in dehydrogenative alcohol coupling (DAC) reactions. Notably, high conversions were achieved with Ru loadings as low as 0.25 mol %. The DAC reactions were systematically investigated to control the product distribution, switching the selectivity from Guerbet alcohol formation to carboxylic acid formation by simply changing the reaction conditions. This selectivity shift was achieved by manipulating the reaction mechanism through conducting the reactions under static nitrogen flow, in air, or in the presence of a hydrogen acceptor molecule. Furthermore, the potential of the DAC system was explored in tandem dehydrogenation/hydrogenation processes, enabling efficient hydrogenation of alkenes and alkynes. Remarkably, the system exhibited high selectivity (85%) and nearly quantitative conversion (99%) toward the formation of E-stilbene when benzyl alcohol was employed as the hydrogen source in the tandem dehydrogenation/hydrogenation sequence, even under high 1-octanol/Ru ratios (5500:1, mol/mol). Hydrogen production performance of the catalytic system, Hoveyda–Grubbs second-generation/pyridine, was evaluated using different alcohols such as methanol, ethanol, and 1-octanol, reaching TON values up to 1300.

Ensuring the quality and safety of synthetic oligonucleotide drug substances demands stringent microbial contamination control. While chemical synthesis inherently carries a lower risk compared with biological manufacturing, robust controls remain critical to minimize potential microbial proliferation at specific stages of the process. Given the limited regulatory guidance directly addressing oligonucleotides, effective contamination control strategies must be built upon thorough risk assessments and established best practices. This work, drawing on the collective expertise of the European Pharma Oligonucleotide Consortium, provides comprehensive recommendations for microbiological control in oligonucleotide manufacturing. Key points include facility design, environmental monitoring, equipment cleaning, in-process controls, and analytical methods. A thorough risk assessment and a holistic approach to microbial management are advocated. Detailed methodologies for risk evaluation, mitigation, and acceptance of residual risks are outlined. This strategic framework aims to proactively manage potential microbiological hazards, ensuring the consistent production of high-quality oligonucleotide therapeutics.

In this work, a new chemo-enzymatic synthesis of (R)-perillaldehyde ((R)-1, 98% ee) was developed by progressively improving the sustainability of the reaction steps. The key transformation is the oxidation of (R)-perillyl alcohol ((R)-2), catalyzed by a recombinant alcohol dehydrogenase from Geobacillus stearothermophilus (ADH-hT), used as cell-free extract (CFE), in the presence of acetone as a sacrificial substrate. Alcohol (R)-2 is obtained in a mixture (44% by NMR analysis) with secondary alcohols 4 and 5 in a two-step sequence starting from the rearrangement of (4R)-limonene oxides catalyzed by aluminum isopropylate in toluene and subsequent allylic rearrangement of the intermediates by S_N2′ displacement in aqueous acetone. Perillyl alcohol is recovered by column chromatography and oxidized with ADH-hT as a catalyst to afford (R)-perillaldehyde (98% ee), which is isolated in pure form by distillation under reduced pressure (22% isolated yield from limonene oxides). When the reaction is performed on the crude mixture containing perillyl alcohol together with the secondary alcohols 4 and 5 as side products, complete chemoselectivity toward the oxidation of the primary alcohol is observed. Thus, we also describe the chemoselective oxidation of alcohol 2 in this mixture (44% by NMR analysis) by means of ADH-hT and subsequent isolation of the corresponding aldehyde by formation of the Bertagnini adduct. A comparison between these two routes and those described in the literature is herein discussed.

With massive production, the agrochemical and specialty chemical industries have seen a sharp increase in the transition from batch to continuous production for highly exothermic processes. This is also true for fine chemicals and pharmaceuticals processes, typically conducted in a batch mode. Highly exothermic reactions can lead to runaway situations, resulting in severe and fatal accidents. Converting batch processes into continuous operation with minimum inventory or holdup in the reactor improves process safety and controllability. A continuous process was developed in this work to produce the key intermediate of silicon-based fungicide flusilazole, which consists of a dual column for Grignard reagent preparation followed by a substitution reaction in a two-stage microreactor system. Herein, we disclose the studies performed to explore a continuous flow process, the reaction parameters of which can be altered as per the process requirements for the completion of the reaction. The improved process explores better heat and mass transfer compared to the batch process, leading to maximum conversion with minimum byproduct formation and high selectivity. The developed process increases production capacity compared to that of the batch process. Handling of moisture-sensitive reagents and high exothermicity were overcome using a two-stage continuous flow reactor. Drastic reduction of reaction time and yield improvement were executed by using a two-stage continuous flow reactor system.