A Tandem Ring Closure and Nitrobenzene Reduction with Sulfide Provides an Improved Route to an Important Intermediate for the Anti-Tuberculosis Drug Candidate Sutezolid.

Sutezolid is an in-development thiomorpholine derivative of the FDA-approved tuberculosis (TB) treatment linezolid. Current synthetic routes for preparing sutezolid start with thiomorpholine as a key structural building block; unfortunately, this material was identified as a major cost driver for the API, which will limit the potential uptake of this treatment in lower income regions. In this work, an alternative, lower-cost synthetic strategy to a known -phenylenediamine intermediate to sutezolid has been demonstrated.

Application of Chiral Transfer Reagents to Improve Stereoselectivity and Yields in the Synthesis of the Antituberculosis Drug Bedaquiline.

Bedaquiline (BDQ) is an important drug for treating multidrug-resistant tuberculosis (MDR-TB), a worldwide disease that causes more than 1.6 million deaths yearly. The current synthetic strategy adopted by the manufacturers to assemble this molecule relies on a nucleophilic addition reaction of a quinoline fragment to a ketone, but it suffers from low conversion and no stereoselectivity, which subsequently increases the cost of manufacturing BDQ.

Development of a Practical Synthesis of the Fragment of OPC-167832.

A concise and practical synthesis has been developed to provide the 8-fluoro-5-hydroxy-3,4-diydrocarbostyril () fragment of OPC-167832 in 41% yield and in >99% purity over four steps from 3-amino-4-fluorophenol. The key feature of this process is the development of a telescoped one-pot synthesis of the quinolone via a chemoselective amidation/acid-induced cyclization that allows for simple product isolation without the need for column chromatography.

Facile and Scalable Methodology for the Pyrrolo[2,1-][1,2,4]triazine of Remdesivir.

Pyrrolo[2,1-][1,2,4]triazine () is an important regulatory starting material in the production of the antiviral drug remdesivir. Compound was produced through a newly developed synthetic methodology utilizing simple building blocks such as pyrrole, chloramine, and formamidine acetate by examining the mechanistic pathway for the process optimization exercise. Triazine was obtained in 55% overall yield in a two-vessel-operated process.

Toward a Practical, Nonenzymatic Process for Investigational COVID-19 Antiviral Molnupiravir from Cytidine: Supply-Centered Synthesis.

A scalable four-step synthesis of molnupiravir from cytidine is described herein. The attractiveness of this approach is its fully chemical nature involving inexpensive reagents and more environmentally friendly solvents such as water, isopropanol, acetonitrile, and acetone. Isolation and purification procedures are improved in comparison to our earlier study as all intermediates can be isolated via recrystallization.

Synthesis of an Oxathiolane Drug Substance Intermediate Guided by Constraint-Driven Innovation.

A new route was developed for construction of the oxathiolane intermediate used in the synthesis of lamivudine (3TC) and emtricitabine (FTC). We developed the presented route by constraining ourselves to low-cost, widely available starting materials-we refer to this as supply-centered synthesis. Sulfenyl chloride chemistry was used to construct the framework for the oxathiolane from acyclic precursors.

Expanding Access to Remdesivir via an Improved Pyrrolotriazine Synthesis: Supply Centered Synthesis.

Pyrrolotriazine is an important precursor to remdesivir. Initial results toward an efficient synthesis are disclosed consisting of sequential cyanation, amination, and triazine formation beginning from pyrrole. This route makes use of highly abundant, commoditized raw material inputs.

An Economical Route to Lamivudine Featuring a Novel Strategy for Stereospecific Assembly.

An economical synthesis of lamivudine was developed by employing a new method to establish the stereochemistry about the heterocyclic oxathiolane ring. Toward this end, an inexpensive and readily accessible lactic acid derivative served the dual purpose of activating the carbohydrate's anomeric center for N-glycosylation and transferring stereochemical information to the substrate simultaneously. Both enantiomers of the lactic acid derivative are available, and either β-enantiomer in this challenging class of 2'-deoxynucleoside active pharmaceutical ingredients can be formed.

Analysis and Isolation of Potential Artemisinin Precursors from Waste Streams of Extraction.

High-performance liquid chromatography, liquid chromatography-mass spectrometry, and gas chromatography-mass spectrometry methods were developed to analyze the process waste streams of extraction. Results from these methods suggested that the final waste from the extraction process could serve as a source of dihydroartemisinic acid (DHAA) that could be converted to additional artemisinin. Two additional impurities were isolated and identified in the waste material as well as in leaf samples.

Practical Synthesis of the Bicyclic Darunavir Side Chain: (3,3a,6a)-Hexahydrofuro[2,3-]furan-3-ol from Monopotassium Isocitrate.

A practical synthesis of (3,3a,6a)-hexahydrofuro[2,3-]furan-3-ol-a key intermediate in the synthesis of darunavir-from monopotassium isocitrate is described. The isocitric acid salt, obtained from a high-yielding fermentation fed by sunflower oil, was converted in several steps to a tertiary amide. This amide, along with the compound's ester functionalities, was reduced with lithium aluminum hydride to give, on acidic workup, a transient aminal-triol.

Identification of impurities in artemisinin, their behavior in high performance liquid chromatography and implications for the quality of derived anti-malarial drugs.

Previous work [1] on the HPLC analysis of artemisinin tentatively identified the two impurities present above trace levels. This identification was based on LC-MS results and NMR of impurities isolated from artemisinin. In this work the impurities have been synthesized allowing verification of their identity by LC-MS.

High performance liquid chromatographic evaluation of artemisinin, raw material in the synthesis of artesunate and artemether.

A barrier to the development of artemisinin derivative based combination treatment of malaria is the lack of defined specifications and purity test methods for the raw material artemisinin. An HPLC method previously published in the International Pharmacopoeia to evaluate purity of artemisinin as an active pharmaceutical ingredient is adapted for use. Excellent method precision and linearity are demonstrated along with observations of robustness.

Use of elevated flow rates in preparative subcritical fluid chromatography.

The benefits of using high flow rates in preparative subcritical fluid chromatography are explored. It is demonstrated that chromatograms loaded to onset of peak coalescence do not deteriorate as flow increases. This allows separation of material in very short time periods leading to dramatically increased production rates.

The effect of acidic and basic additives on the enantioseparation of basic drugs using polysaccharide-based chiral stationary phases.

The enantioseparation of nine commercially available basic drugs was achieved on polysaccharide-based chiral stationary phases with the acidic additive ethanesulfonic acid and the basic additive butylamine. Seven different commercially available CSPs were used for the study (AD, AS, OD, OJ, OG, OB, and OC). Mobile phase additives have been proven to be essential in obtaining satisfactory enantio-resolution in terms of both efficiency and selectivity.

Chiral separations on polysaccharide stationary phases using polar organic mobile phases.

About 30% of a chemically diverse set of compounds were found to separate on four polysaccharide chiral stationary phases using polar organic mobile phases. No structural features appeared to correlate to successful separations. Titrations between normal and polar organic mobile phases suggested that separation mechanisms do not differ between these mobile phases.

Chiral separation of amines by high-performance liquid chromatography using polysaccharide stationary phases and acidic additives.

A dramatic and beneficial effect of ethanesulfonic acid (ESA) on the chiral HPLC separation of basic compounds was found. Using a single chiral column and a starting mobile phase, more than half of a diverse set of amines was baseline separated. Changing alcohol content and alcohol type increased the success rate.

Chiral separation of amines in subcritical fluid chromatography using polysaccharide stationary phases and acidic additives.

The chiral separation of basic compounds by subcritical fluid chromatography (SFC) is often unsuccessful, due possibly to multiple interactions of the analyte with the mobile and stationary phase. Incorporation of a strong acid, ethanesulfonic acid (ESA), into the sample diluent and mobile phase modifier gives a dramatic improvement in these separations. Screening with ethanol containing 0.

Origin of enhanced chiral selectivity by acidic additives for a polysaccharide-based stationary phase.

The effects of ethanesulfonic acid (ESA) and n-butylamine as additives were studied for a wide variety of chiral compounds using the polysaccharide chiral stationary phase (CSP), Chiralpak AD. The mobile phase consisted of hexane-ethanol (90:10, v/v). The additives typically had small effects, with one exception: the acidic additive had an enormous effect on the chiral selectivity of amino acid esters.

Memory effect of diethylamine mobile phase additive on chiral separations on polysaccharide stationary phases.

The existence of a memory effect for amine additives on polysaccharide chiral stationary phases has often been suggested, but not clearly demonstrated. Demonstration of this effect is made difficult by the uncertainty as to which analytes benefit from use of amine additives and, typically, an unclear history of column use. In this work, analytes were selected for differences in their behavior with and without additives.

Effect of amine mobile phase additives on chiral subcritical fluid chromatography using polysaccharide stationary phases.

Increased retention and selectivity in the subcritical fluid chromatography (SFC) of various amine compounds on polysaccharide chiral stationary phases (CSP) was observed upon incorporation of cyclic amines into the modifier. The retention increases are most pronounced with 2-propanol and are almost absent when methanol is used as modifier. This suggests that the effect may arise from a restriction to the modifier access to the binding site required to effect elution.

Enantioseparation of amino acids on a polysaccharide-based chiral stationary phase.

Sulfonic acids have been shown to be more effective than the commonly used trifluoroacetic acid (TFA) in the chiral resolution of underivatized aromatic amino acids on an amylosic column. Sulfonic acid additives give a more UV transparent mobile phase, possibly allowing the detection of non-aromatic analytes. Work presented demonstrates that through the combination of sulfonic acid mobile phase additives, amine mobile phase additives and solvent modifier variations, the enantiomers of 20 of 25 probe amino acids are fully resolved, four are partially resolved with only one failing to be separated on a common amylosic column.

Memory effect of mobile phase additives in chiral separations on a Chiralpak AD column.

Using chiral probes shown to be sensitive to the presence of mobile phase additives, a memory effect for these additives by an amylosic column was demonstrated. Exposure to these additives gave prolonged chromatographic performance changes even after their removal from the mobile phase. This finding is consistent with strong binding of the additives to the stationary phase.