Synthesis of the CETP Inhibitor Torcetrapib: The Resolution Route and Origin of Stereoselectivity in the Iminium Ion Cyclization

Catalytic, Asymmetric Michael-Aldol Annulations via a Stereodivergent/Stereoconvergent Path Operating under Curtin-Hammett Control

A bifunctional iminophosphorane (BIMP)-catalyzed method for the synthesis of densely functionalized cyclohexanols establishes five contiguous stereocenters (diastereoselection up to >20:1, enantioselectivity up to >99:1) in a Michael/aldol domino reaction between trisubstituted electrophilic alkenes and γ-nitroketones. Mechanistic studies suggest a scenario in which stereoconvergency is achieved by kinetically controlled cyclization after the initial diastereodivergent Michael addition. Diastereoconvergency during cyclization is shown to result from Curtin-Hammett kinetics, a finding that contrasts the crystallization-driven stereoconvergency previously reported in similar systems. Despite the change in the stereocontrol mechanism, the operational attributes remain attractive, with the crystalline products typically isolated in analytically pure form upon filtration of the reaction mixture.

Sterically Demanding Flexible Phosphoric Acids for Constructing Efficient and Multi-Purpose Asymmetric Organocatalysts

Herein, we present a novel approach for various asymmetric transformations of cyclic enones. The combination of readily accessible chiral diamines and sterically demanding flexible phosphoric acids resulted in a simple and highly tunable catalyst framework. The careful optimization of the catalyst components led to the identification of a particularly powerful and multi-purpose organocatalyst, which was successfully applied for asymmetric epoxidations, aziridinations, aza-Michael-initiated cyclizations, as well as for a novel Robinson-like Michael-initiated ring closure/aldol cyclization. High catalytic activities and excellent stereocontrol was observed for all four reaction types, indicating the excellent versatility of our catalytic system. Furthermore, a simple change in the diamine's configuration provided easy access to both product antipodes in all cases.

Sterically Demanding Flexible Phosphoric Acids for Constructing Efficient and Multi‐Purpose Asymmetric Organocatalysts

Herein, we present a novel approach for various asymmetric transformations of cyclic enones. The combination of readily accessible chiral diamines and sterically demanding flexible phosphoric acids resulted in a simple and highly tunable catalyst framework. The careful optimization of the catalyst components led to the identification of a particularly powerful and multi‐purpose organocatalyst, which was successfully applied for asymmetric epoxidations, aziridinations, aza‐Michael‐initiated cyclizations, as well as for a novel Robinson‐like Michael‐initiated ring closure/aldol cyclization. High catalytic activities and excellent stereocontrol was observed for all four reaction types, indicating the excellent versatility of our catalytic system. Furthermore, a simple change in the diamine's configuration provided easy access to both product antipodes in all cases.

Design, Synthesis, and Characterization of I-BET567, a Pan-Bromodomain and Extra Terminal (BET) Bromodomain Oral Candidate

Through regulation of the epigenome, the bromodomain and extra terminal (BET) family of proteins represent important therapeutic targets for the treatment of human disease. Through mimicking the endogenous N-acetyl-lysine group and disrupting the protein-protein interaction between histone tails and the bromodomain, several small molecule pan-BET inhibitors have progressed to oncology clinical trials. This work describes the medicinal chemistry strategy and execution to deliver an orally bioavailable tetrahydroquinoline (THQ) pan-BET candidate. Critical to the success of this endeavor was a potency agnostic analysis of a data set of 1999 THQ BET inhibitors within the GSK collection which enabled identification of appropriate lipophilicity space to deliver compounds with a higher probability of desired oral candidate quality properties. SAR knowledge was leveraged via Free-Wilson analysis within this design space to identify a small group of targets which ultimately delivered I-BET567 (27), a pan-BET candidate inhibitor that demonstrated efficacy in mouse models of oncology and inflammation.

Enantio- and diastereoselective double Mannich reaction of malononitrile with N-Boc imines using quinine-derived bifunctional organoiodine catalyst

A chiral quinine-derived organic base catalyst with halogen bond donor functionality was used to catalyze the asymmetric double Mannich reaction of malononitrile with N-Boc and N-Cbz imines to afford 1,3-diamines in excellent yields with high enantio- and diastereoselectivities. With 2.2 equiv. of a single imine electrophile, symmetrical 1,3-diamines were obtained, whereas, with two different imine partners, unsymmetrically substituted 1,3-diamine was obtained. The monohydration of the double Mannich product was also achieved.

Enamides and dienamides in phosphoric acid-catalysed enantioselective cycloadditions for the synthesis of chiral amines

This feature article describes how enamides and dienamides can participate in chiral phosphoric acid catalyzed enantioselective cycloadditions to prepare a wide range of cyclic amines.

Recent advances of the Povarov reaction in medicinal chemistry

The Povarov multicomponent reaction consists on the condensation of an aniline, an aldehyde, and an activated olefin to generate a tetrahydroquinoline adduct with 3 diversity points. Hereby, we report the main features of this transformation and its uses in medicinal chemistry. Relevant examples of the impact of Povarov adducts in different therapeutic areas are provided.

3H-pyrazolo[4,3-f]quinoline haspin kinase inhibitors and anticancer properties

Histone modification, a post-translational modification of histones and involving various covalent tags, such as methyl, phosphate and acetate groups, affects gene expression and hence modulates various cellular events, including growth and proliferation. Consequently histone-modifying proteins have become targets for the development of anticancer agents. Thus far, compounds that inhibit the methylation or acetylation of histones have advanced in the clinic, but inhibitors of histone phosphorylation have lagged behind. Haspin is a kinase that phosphorylates histone H3 and is a promising anticancer target. Thus far only a handful of haspin inhibitors have been reported. Using a one-flask Doebner/Povarov reaction, we synthesized a library of compounds that potently inhibit haspin with IC50 values as low as 14 nM. Some of these compounds also inhibited the proliferation of cancer cell lines HCT116, HeLa and A375. The ease of synthesis of the new haspin inhibitors, coupled with their anticancer activities make these compounds interesting leads to develop into therapeutics.

Total facial selectivity of a d-erythrosyl aromatic imine in [4π + 2π] cycloadditions; synthesis of 2-alkylpolyol 1,2,3,4-tetrahydroquinolines

Different electron-rich dienophiles were combined with the imine obtained from 2,4-O-benzylidene-d-erythrose and p-anisidine furnishing enantiomerically pure tetrahydroquinolines, by inverse electron-demand [4π + 2π] cycloaddition.

The structure based design of dual HDAC/BET inhibitors as novel epigenetic probes

DUAL946 (1) inhibits BET and HDAC proteins in chemoproteomic cell lysate experiments and in immune and cancer cells.

Development and validation of an enantioselective HPLC–UV method using Chiralpak AD-H to quantify (+)- and (−)-torcetrapib enantiomers in hamster plasma—application to a pharmacokinetic study

A chiral selective, accurate and reproducible high-performance liquid chromatographic (HPLC) method was developed and validated for direct separation of individual enantiomers of torcetrapib (TTB) [(+)-TTB and (-)-TTB]. TTB enantiomers and IS were extracted from a small aliquot of plasma (100 microL) by simple liquid-liquid extraction using acetonitrile as extraction solvent. The enantiomers were resolved on Chiralpak AD-H (250 mm x 4.6 mm, 5 microm) with the mobile phase consisting of n-hexane:isopropyl alcohol (IPA) in the ratio of 95:5 (v/v). The eluate was monitored using an UV detector set at 254 nm. Baseline separation of the TTB enantiomers and the internal standard (IS, DRL-17859), free from endogenous interferences was achieved. The resolution factor between the enantiomers was optimized and found to be not less than five. During method development, the IPA content in the mobile phase was optimized for separation of peaks of interest. Additionally, both flow rate and column temperature were optimized for an improved baseline separation of the enantiomers. Ratio of peak area of each enantiomer to IS was used for quantification of plasma samples. Nominal retention times of (+)-TTB, (-)-TTB and IS were 9.4, 13.8 and 17.5 min, respectively. The standard curves for TTB enantiomers were linear (r(2)>0.999) in the concentration range 0.1-10 microg/mL for each enantiomer. Absolute recovery, when compared to neat standards, was 88.7-90.0% for TTB enantiomers and 100% for IS from the hamster plasma. The lower limit of quantification (LLOQ) for each enantiomer of TTB was 0.1 microg/mL. The inter-day precisions were in the range of 4.57-6.32 and 5.66-11.0% for (+)-TTB and (-)-TTB, respectively. The intra-day precisions were in the range of 1.60-7.36 and 2.76-13.6% for (+)-TTB and (-)-TTB, respectively. Accuracy in the measurement of quality control (QC) samples was in the range of 95.6-109% and 92.7-108% for (+)-TTB and (-)-TTB, respectively. Both enantiomers were stable in a series of stability studies, viz. bench-top (up to 12h), auto-sampler (up to 24h) and freeze/thaw cycles (n=3). Stability of TTB enantiomers was established in hamster plasma for 15 days at -80 degrees C. The application of the assay to a pharmacokinetic study of (-)-TTB in hamsters is described.