First generation design, synthesis, and evaluation of azepine-based cryptophycin analogues

Asymmetric construction of allylicstereogenic carbon center featuring atrifluoromethyl group via enantioselective reductive fluoroalkylation

Emerging as a powerful tool for lead optimization in pharmaceutical research and development, to develop the facile, general protocols that allows the incorporation of fluorine-containing motif in drug candidates has accumulated enormous research interest in recent years. Among these important motifs, the incorporation of strategic motif CF₃ on aliphatic chain especially with the concomitant construction of trifluoromethylated alkanes bearing a CF₃-substituted stereogenic carbon, is of paramount importance. Herein, we disclose an asymmetric nickel-catalyzed reductive trifluoroalkylation of alkenyl halides for enantioselective syntheses of diverse α-trifluoromethylated allylic alkanes, offering a general protocol to access the trifluoromethyl analogue to chiral α-methylated allylic alkanes, one of the most prevalent key components among natural products and pharmaceuticals. Utilities of the method including the application of the asymmetric trifluoroalkylation on multiple biologically active complex molecules, derivatization of transformable alkenyl functionality were demonstrated, providing a facile method in the diversity-oriented syntheses of CF₃-containing chiral drugs and bioactive-molecules.

Transition-metal-free, mild and efficient ring expansion of amino acid derivatives: facile access to densely functionalized azepines

A mild, practical and efficient approach for the synthesis of valuable azepine products was achieved by the ring expansion of easily accessible amino acid derivatives.

Synthesis of α-Deuterated Primary Amines via Reductive Deuteration of Oximes Using D2O as a Deuterium Source

Selective introduction of the deuterium atom into the α-position of amines is important for the development of all types of novel deuterated drugs and agrochemicals due to the pervasive presence of amines. In this study, we report the first general single-electron-transfer reductive deuteration of both ketoximes and aldoximes using SmI₂ as an electron donor and D₂O as a deuterium source for the synthesis of α-deuterated primary amines with excellent levels of deuterium incorporations (>95% [D]). This protocol exhibits excellent chemoselectivity and tolerates a variety of functional groups. The potential application of this new method was showcased in the synthesis of deuterated drugs, such as rimantadine-d₄, the tebufenpyrad analogue, derivatives of nabumetone and pregnenolone, and a series of building blocks for the rapid and general assembly of deuterated drugs and pesticides.

Bifunctional N-heterocyclic carbene catalyzed [3 + 4] annulation of enals with azadienes: enantioselective synthesis of benzofuroazepinones

The bifunctional N-heterocyclic carbene catalyzed [3 + 4] annulation of enals with aurone-derived azadienes was developed to afford benzofuroazepinones with excellent enantioselectivities.

Tubulin Inhibitor-Based Antibody-Drug Conjugates for Cancer Therapy

Antibody-drug conjugates (ADCs) are a class of highly potent biopharmaceutical drugs generated by conjugating cytotoxic drugs with specific monoclonal antibodies through appropriate linkers. Specific antibodies used to guide potent warheads to tumor tissues can effectively reduce undesired side effects of the cytotoxic drugs. An in-depth understanding of antibodies, linkers, conjugation strategies, cytotoxic drugs, and their molecular targets has led to the successful development of several approved ADCs. These ADCs are powerful therapeutics for cancer treatment, enabling wider therapeutic windows, improved pharmacokinetic/pharmacodynamic properties, and enhanced efficacy. Since tubulin inhibitors are one of the most successful cytotoxic drugs in the ADC armamentarium, this review focuses on the progress in tubulin inhibitor-based ADCs, as well as lessons learned from the unsuccessful ADCs containing tubulin inhibitors. This review should be helpful to facilitate future development of new generations of tubulin inhibitor-based ADCs for cancer therapy.

Toward the development of chemoprevention agents. Part 1: Design, synthesis, and anti-inflammatory activities of a new class of 2,5-disubstituted-dioxacycloalkanes

A new class of 2,5-disubstituted-dioxacycloalkanes were designed and synthesized via stereoselective synthetic method as cancer chemoprevention agents. The anti-inflammatory activities of these compounds were tested using the xylene-induced mouse ear edema model. Some of these compounds exhibited comparable or better anti-inflammatory activities than that of aspirin suggesting that they can be further developed as potential anti-inflammatory drug lead compounds. In addition, treatment of these anti-inflammatory agents did not prolong tail bleeding time in mice. The structure/activity relationships were also analyzed among these compounds.

Stereoselective synthesis and anti-inflammatory activities of 6- and 7-membered dioxacycloalkanes

A class of 5-trifluoroacetylamino-1,3-dioxacycloalkanes, 5-benzoylamino-1,3-dioxacycloalkanes, and 5-amino-1,3-dioxacycloalkane compounds were stereoselectively synthesized as potential anti-inflammatory drug candidates. The anti-inflammatory activities of these compounds were tested using the xylene-induced mouse ear edema model, from which multiple compounds possessing anti-inflammatory properties which surpass aspirin were identified; these compounds were then compared to establish structure-activity relationships.

Biological evaluation of cryptophycin 52 fragment A analogues: Effect of the multidrug resistance ATP binding cassette transporters on antitumor activity

Cryptophycin 52 (LY355703) is a potent antiproliferative analogue of the marine natural product cryptophycin 1. It has been shown to have a broad range of antitumor activity against human tumor xenografts and murine tumors including tumors resistant to Taxol and Adriamycin. Its mechanism of action involves arresting cells in the G2-M phase of the cell cycle by binding to microtubules and suppressing their dynamics. This 16-membered depsipeptide can be divided into four major subunits or fragments (A–D). We reported previously on our synthetic efforts around fragment A and discovered that this region of the molecule was amenable to a structure-activity relationship study that resulted in highly active antiproliferative agents when evaluated in the CEM leukemia cell line. The synthetic analogues were designed to help improve the efficacy and aqueous solubility of the parent compound; therefore, many in this series contained ionizable functional groups such as an amino group, a hydroxy group, or a carboxylic acid. Although several of these analogues showed improvements in potency over cryptophycin 52 in drug-sensitive tumor xenograft models, many lost their activity against Adriamycin-resistant tumor lines. It was discovered on additional in vitro evaluation that these analogues became good substrates of the multidrug resistance transporter P-glycoprotein.

Exploring privileged structures: the combinatorial synthesis of cyclic peptides

Head-to-tail cyclic peptides have been reported to bind to multiple, unrelated classes of receptor with high affinity. They may therefore be considered to be privileged structures. This review outlines the strategies by which both macrocyclic cyclic peptides and cyclic dipeptides or diketopiperazines have been synthesised in combinatorial libraries. It also briefly outlines some of the biological applications of these molecules, thereby justifying their inclusion as privileged structures.

Exploring privileged structures: the combinatorial synthesis of cyclic peptides

Head-to-tail cyclic peptides have been reported to bind to multiple, unrelated classes of receptor with high affinity. They may therefore be considered to be privileged structures. This review outlines the strategies by which both macrocyclic cyclic peptides and cyclic dipeptides or diketopiperazines have been synthesised in combinatorial libraries. It also briefly outlines some of the biological applications of these molecules, thereby justifying their inclusion as privileged structures.