Ryan A. Bragg

Isothiourea-Mediated Stereoselective C-Acylation of Silyl Ketene Acetals

Isothiourea DHPB promotes the diastereoselective C-acylation of silyl ketene acetals with anhydrides or benzoyl fluoride, giving 3-acyl-3-aryl or 3-acyl-3-alkylfuranones in excellent yields and stereoselectivities (up to 99:1 dr).

Isothiourea-catalysed asymmetric C-acylation of silyl ketene acetals

Screening of a range of chiral isothioureas and acyl donors to promote the asymmetric C-acylation of silyl ketene acetals indicates that C(2)-aryl-dihydropyrimidobenzothiazole-derived isothioureas and propionic anhydride give optimal reactivity and enantioselectivity in this process. Under optimised conditions 3-acyl-3-aryl or 3-acyl-3-alkylfuranones are prepared in good yields and moderate to excellent enantioselectivities (up to 98% ee; ee=enantiomeric excess).

Isotope chemistry; a useful tool in the drug discovery arsenal.

As Medicinal Chemists are responsible for the synthesis and optimization of compounds, they often provide intermediates for use by isotope chemistry. Nevertheless, there is generally an incomplete understanding of the critical factors involved in the labeling of compounds. The remit of an Isotope Chemistry group varies from company to company, but often includes the synthesis of compounds labeled with radioisotopes, especially H-3 and C-14 and occasionally I-125, and stable isotopes, especially H-2, C-13, and N-15. Often the remit will also include the synthesis of drug metabolites. The methods used to prepare radiolabeled compounds by Isotope Chemists have been reviewed relatively recently. However, the organization and utilization of Isotope Chemistry has not been discussed recently and will be reviewed herein.

Isothiourea-Mediated Asymmetric O- to C-Carboxyl Transfer of Oxazolyl Carbonates: Structure–Selectivity Profiles and Mechanistic Studies

The structural motif within a series of tetrahydropyrimidine-based isothioureas necessary for generating high asymmetric induction in the asymmetric Steglich rearrangement of oxazolyl carbonates is fully explored, with crossover and dynamic (19)F NMR experiments used to develop a mechanistic understanding of this transformation.

The synthesis of tritium, carbon-14 and stable isotope labelled selective estrogen receptor degraders.

As part of a Medicinal Chemistry program aimed at developing an orally bioavailable selective estrogen receptor degrader, a number of tritium, carbon-14, and stable isotope labelled (E)-3-[4-(2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-yl)phenyl]prop-2-enoic acids were required. This paper discusses 5 synthetic approaches to this compound class.

The synthesis of a tritium, carbon‐14, and stable isotope‐labeled cathepsin C inhibitors

As part of a medicinal chemistry program aimed at developing a highly potent and selective cathepsin C inhibitor, tritium, carbon-14, and stable isotope-labeled materials were required. The synthesis of tritium-labeled methanesulfonate 5 was achieved via catalytic tritiolysis of a chloro precursor, albeit at a low radiochemical purity of 67%. Tritium-labeled AZD5248 was prepared via a 3-stage synthesis, utilizing amide-directed hydrogen isotope exchange. Carbon-14 and stable isotope-labeled AZD5248 were successfully prepared through modifications of the medicinal chemistry synthetic route, enabling the use of available labeled intermediates.

New trends and applications in carboxylation for isotope chemistry

Carboxylations are an important method for the incorporation of isotopically labeled 14CO2 into molecules. This manuscript will review labeled carboxylations since 2010 and will present a perspective on the potential of recent unlabeled methodology for labeled carboxylations. The perspective portion of the manuscript is broken into 3 major sections based on product type, arylcarboxylic acids, benzylcarboxylic acids, and alkyl carboxylic acids, and each of those sections is further subdivided by substrate.

Isotope Labelling by Reduction of Nitriles: Application to the Synthesis of Isotopologues of Tolmetin and Celecoxib

The aryl methyl group is found in many drug-like compounds, but there are limited ways of preparing compounds with an isotope label in this methyl position. The process of cyanation of an aryl halide followed by complete reduction of the nitrile to a methyl group was investigated as a route for preparing stable and radiolabelled isotopologues of drug-like compounds. Using this methodology, carbon-13, deuterium, carbon-14, and tritium labelled isotopologues of the nonsteroidal anti-inflammatory drug tolmetin were produced, as well as carbon-13, deuterium, and carbon-14 labelled isotopologues of another nonsteroidal anti-inflammatory drug, celecoxib. The radiolabelled compounds were produced at high specific activity and the stable isotope labelled compounds with high incorporation making them suitable for use as internal standards in mass spectrometry assays. This approach provides a common synthetic route to multiple isotopologues of compounds using inexpensive and readily available labelled starting materials.