A Highly Convergent Total Synthesis of Leustroducsin B.

Leustroducsin B exhibits a large variety of biological activities and unique structural features. An efficient and highly convergent total synthesis of Leustroducsin B was achieved in 17 longest linear and 39 total steps by disconnecting the molecule into three fragments having similar levels of complexity. These pieces were connected via a highly efficient chelate-controlled addition of a vinyl zincate to an α-hydroxy ketone and a silicon-mediated cross-coupling. The stereochemistry of the central and western fragments was set catalytically in high yields and excellent de by a zinc-ProPhenol-catalyzed aldol reaction and a palladium-catalyzed asymmetric allylic alkylation.

The importance of hydrogen bonding to stereoselectivity and catalyst turnover in gold-catalyzed cyclization of monoallylic diols.

Density functional calculations and experiment were used to examine the mechanism, reactivity, and origin of chirality transfer in monophosphine Au-catalyzed monoallylic diol cyclization reactions. The lowest energy pathway for cyclization involves a two-step sequence that begins with intramolecular C-O bond formation by anti-addition of the non-allylic hydroxyl group to the Au-coordinated alkene followed by concerted hydrogen transfer/anti-elimination to liberate water. Concerted S(N)2'-type transition states were found to be significantly higher in energy. The two-step cyclization pathway is extremely facile due to hydrogen bonding between diol groups that induces nucleophilic attack on the alkene and then proton transfer between diol groups after C-O bond formation. Importantly, intramolecular proton transfer and elimination provides an extremely efficient avenue for catalyst regeneration from the Au-C σ-bond intermediate, in contrast to other Au-catalyzed cyclization reactions where this intermediate severely restricts catalyst turnover. The origin of chirality transfer and the ensuing alkene stereochemistry is also the result of strong hydrogen-bonding interactions between diol groups. In the C-O bond-forming step, requisite hydrogen bonding biases the tethered nucleophilic moiety to adopt a chair-like conformation with substituents in either axial or equatorial positions, dictating the stereochemical outcome of the reaction. Since this hydrogen bonding is maintained throughout the course of the reaction, establishment of the resultant olefin geometry is also attributed to this templating effect. These computational conclusions are supported by experimental evidence employing bicyclic systems to probe the facial selectivity.

A comparative study of the Au-catalyzed cyclization of hydroxy-substituted allylic alcohols and ethers.

The Au(I)-catalyzed cyclization of hydroxyallylic ethers to form tetrahydropyrans is reported. Employing (acetonitrile)[(o-biphenyl)di-tert-butylphosphine]gold(I) hexafluoroantimonate, the cyclization reactions were complete within minutes to hours, depending on the substrate. The reaction progress was monitored by GC, and comparisons between substrates demonstrate that reactions of allylic alcohols are faster than the corresponding ethers. Additionally, it is reported that Reaxa QuadraPure(TM) MPA is an efficient scavenging reagent that halts the reaction progress.

Novel, Selective Inhibitors of USP7 Uncover Multiple Mechanisms of Antitumor Activity In Vitro and In Vivo.

The deubiquitinase USP7 regulates the levels of multiple proteins with roles in cancer progression and immune response. Thus, USP7 inhibition may decrease oncogene function, increase tumor suppressor function, and sensitize tumors to DNA-damaging agents. We have discovered a novel chemical series that potently and selectively inhibits USP7 in biochemical and cellular assays. Our inhibitors reduce the viability of multiple TP53 wild-type cell lines, including several hematologic cancer and MYCN-amplified neuroblastoma cell lines, as well as a subset of TP53-mutant cell lines in vitro Our work suggests that USP7 inhibitors upregulate transcription of genes normally silenced by the epigenetic repressor complex, polycomb repressive complex 2 (PRC2), and potentiate the activity of PIM and PI3K inhibitors as well as DNA-damaging agents. Furthermore, oral administration of USP7 inhibitors inhibits MM.1S (multiple myeloma; TP53 wild type) and H526 (small cell lung cancer; TP53 mutant) tumor growth in vivo Our work confirms that USP7 is a promising, pharmacologically tractable target for the treatment of cancer.

Discovery of Potent, Selective, and Orally Bioavailable Inhibitors of USP7 with In Vivo Antitumor Activity.

USP7 is a promising target for cancer therapy as its inhibition is expected to decrease function of oncogenes, increase tumor suppressor function, and enhance immune function. Using a structure-based drug design strategy, a new class of reversible USP7 inhibitors has been identified that is highly potent in biochemical and cellular assays and extremely selective for USP7 over other deubiquitinases. The succinimide was identified as a key potency-driving motif, forming two strong hydrogen bonds to the allosteric pocket of USP7. Redesign of an initial benzofuran-amide scaffold yielded a simplified ether series of inhibitors, utilizing acyclic conformational control to achieve proper amine placement. Further improvements were realized upon replacing the ether-linked amines with carbon-linked morpholines, a modification motivated by free energy perturbation (FEP+) calculations. This led to the discovery of compound 41, a highly potent, selective, and orally bioavailable USP7 inhibitor. In xenograft studies, compound 41 demonstrated tumor growth inhibition in both p53 wildtype and p53 mutant cancer cell lines, demonstrating that USP7 inhibitors can suppress tumor growth through multiple different pathways.

Discovery of a Potent and Selective CCR4 Antagonist That Inhibits Treg Trafficking into the Tumor Microenvironment.

Recruitment of suppressive CD4+ FOXP3+ regulatory T cells (Treg) to the tumor microenvironment (TME) has the potential to weaken the antitumor response in patients receiving treatment with immuno-oncology (IO) agents. Human Treg express CCR4 and can be recruited to the TME through the CC chemokine ligands CCL17 and CCL22. In some cancers, Treg accumulation correlates with poor patient prognosis. Preclinical data suggests that preventing the recruitment of Treg and increasing the population of activated effector T cells (Teff) in the TME can potentiate antitumor immune responses. We developed a novel series of potent, orally bioavailable small molecule antagonists of CCR4. From this series, several compounds exhibited high potency in distinct functional assays in addition to good in vitro and in vivo ADME properties. The design, synthesis, and SAR of this series and confirmation of its in vivo activity are reported.

Au-catalyzed cyclization of monoallylic diols.

The Ph3PAuCl/AgOTf-catalyzed cyclization of monoallylic diols to form tetrahydropyrans is reported. The reactions proceed rapidly at temperatures as low as -78 degrees C with catalyst loadings as low as 0.1 mol % to provide the products in 79-99% yield. A broad range of structurally diverse substrates perform well in the reaction. When 2,6-disubstituted tetrahydropyrans are produced, the reaction is highly diastereoselective for the 2,6-cis product.

Redox cycloisomerization approach to 1,2-dihydropyridines.

The phosphine-catalyzed synthesis of 1,2-dihydropyridines via an alkyne isomerization/electrocyclization sequence is described. Propargylidenecarbamate substrates were prepared following a one-pot procedure between a terminal alkyne, a benzonitrile, and a chloroformate in the presence of trimethylaluminum. This methodology gives access to a diverse set of 2,6-disubstituted 1,2-dihydropyridines in high yield. The products can be easily converted into substituted piperidines or pyridines, and this methodology was applied to the synthesis of indolizidines.

Efficient cobalt-catalyzed oxidative conversion of lignin models to benzoquinones.

Phenolic lignin model monomers and dimers representing the primary substructural units of lignin were successfully oxidized to benzoquinones in high yield with molecular oxygen using new Co-Schiff base catalysts bearing a bulky heterocyclic nitrogen base as a substituent. This is the first example of a catalytic system able to convert both S and G lignin model phenols in high yield, a process necessary for effective use of lignin as a chemical feedstock.

The tandem intermolecular hydroalkoxylation/Claisen rearrangement.

The Au(I)-catalyzed intermolecular hydroalkoxylation of alkynes with allylic alcohols to provide allyl vinyl ethers that subsequently undergo Claisen rearrangement is reported. This new cascade reaction strategy facilitates the direct formation of γ,δ-unsaturated ketones from simple starting materials in a single step.

Chirality transfer in Au-catalyzed cyclization reactions of monoallylic diols: selective access to specific enantiomers based on olefin geometry.

The gold(I)-catalyzed cyclization of monoallylic diols to form tetrahydropyrans is shown to be highly stereoselective when chiral allylic alcohols are employed. Substrates that differ only in olefin geometry provide enantiomeric products from formal S(N)2' reactions in high yields with excellent chirality transfer. The allylic alcohol stereochemistry also efficiently controls the facial selectivity when the substrates include additional stereocenters.

A highly adaptable catalyst/substrate system for the synthesis of substituted chromenes.

The gold(I)-catalyzed endo-cyclization of o-(1-hydroxyallyl)phenols to form chromenes is reported. The title compounds are prepared in high yield from readily available substrates. The system tolerates both electron rich and deficient aryl rings and a high degree of substitution on the allyl moiety.

Synthesis and biological activities of new furo[3,4-b]carbazoles: potential topoisomerase II inhibitors.

New 1,5-dihydro-4-(substituted phenyl)-3H-furo[3,4-b]carbazol-3-ones were synthesised via a key step Diels-Alder reaction under microwave irradiation. 3-Formylindole was successfully used in a 6-step synthesis to obtain those complex heterocycles. The Diels-Alder reaction generating the carbazole ring was optimised under thermal conditions or microwave irradiation. After cleavage of functional groups, DNA binding, topoisomerase inhibition and cytotoxic properties of the new-formed furocarbazoles were investigated. These carbazoles do not present a strong interaction with the DNA, and do not modify the relaxation of the DNA in the presence of topoisomerase I or II except for one promising compound. This compound is a potent topoisomerase II inhibitor, and its cellular activity is not moderated compared to etoposide. The synthesis of these molecules allowed the generalisation of the method using indole and 5-OBn indole and several benzaldehydes. The synthesis of these molecules produced chemical structures endowed with promising cytotoxic and topoisomerase II inhibition activities.