The efficient synthesis and biological evaluation of justicidin B

A facile new synthetic method for the preparation of a Type-A 1-arylnaphthalene lactone skeleton was developed and used to synthesise justicidin B and several derivatives. Key synthesis steps included Hauser-Kraus annulation of a phthalide intermediate and Suzuki-Miyaura cross coupling between a triflated naphthalene lactone intermediate and various potassium organotrifluoroborates. With two exceptions, the derivatives showed significant inhibitory effect on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in mouse macrophages. Moreover, several compounds, including justicidin B, had marked cytotoxicity towards six human tumour cell lines.

The Symbiotic Relationship Between Drug Discovery and Organic Chemistry

All pharmaceutical products contain organic molecules; the source may be a natural product or a fully synthetic molecule, or a combination of both. Thus, it follows that organic chemistry underpins both existing and upcoming pharmaceutical products. The reverse relationship has also affected organic synthesis, changing its landscape towards increasingly complex targets. This Review article sets out to give a concise appraisal of this symbiotic relationship between organic chemistry and drug discovery, along with a discussion of the design concepts and highlighting key milestones along the journey. In particular, criteria for a high-quality compound library design enabling efficient virtual navigation of chemical space, as well as rise and fall of concepts for its synthetic exploration (such as combinatorial chemistry; diversity-, biology-, lead-, or fragment-oriented syntheses; and DNA-encoded libraries) are critically surveyed.

Rationally Designed Semisynthetic Natural Product Analogues for Stabilization of 14-3-3 Protein-Protein Interactions

The natural product family of fusicoccanes are stabilizers of 14-3-3 mediated protein-protein interactions (PPIs), some of which possess antitumor activity. In this study, the first use of molecular dynamics (MD) to rationally design PPI stabilizers with increased potency is presented. Synthesis of a focused library, with subsequent characterization by fluorescence polarization, mutational studies, and X-ray crystallography confirmed the power of the MD-based design approach, revealing the potential for an additional hydrogen bond with the 14-3-3 protein to lead to significantly increased potency. Additionally, these compounds exert their action in a cellular environment with increased potency. The newly found polar interaction could provide an anchoring point for new small-molecule PPI stabilizers. These results facilitate the development of fusicoccanes towards drugs or tool compounds, as well as allowing the study of the fundamental principles behind PPI stabilization.

Generation of Polar Semi-Saturated Bicyclic Pyrazoles for Fragment-Based Drug-Discovery Campaigns

Synthesising polar semi-saturated bicyclic heterocycles can lead to better starting points for fragment-based drug discovery (FBDD) programs. We report the application of diverse chemistry to construct bicyclic systems from a common intermediate, where pyrazole, a privileged heteroaromatic able to bind effectively to biological targets, is fused to diverse saturated counterparts. The generated fragments can be further developed either after confirmation of their binding pose or early in the process, as their synthetic intermediates. Essential quality control (QC) for selection of small molecules to add to a fragment library is discussed.

Scaffold Diversity Synthesis Delivers Complex, Structurally, and Functionally Distinct Tetracyclic Benzopyrones

Complexity-generating chemical transformations that afford novel molecular scaffolds enriched in sp3 character are highly desired. Here, we present a highly stereoselective scaffold diversity synthesis approach that utilizes cascade double-annulation reactions of diverse pairs of zwitterionic and non-zwitterionic partners with 3-formylchromones to generate highly complex tetracyclic benzopyrones. Each pair of annulation partners adds to the common chroman-4-one scaffold to build two new rings, supporting up to four contiguous chiral centers that include an all-carbon quaternary center. Differently ring-fused benzopyrones display different biological activities, thus demonstrating their immense potential in medicinal chemistry and chemical biology research.

A Gold-Catalyzed Domino Cyclization Enabling Rapid Construction of Diverse Polyheterocyclic Frameworks

We report herein an efficient gold(I)-catalyzed post-Ugi domino dearomatization/ipso-cyclization/Michael sequence that enables access to libraries of diverse (hetero)arene-annulated tricyclic heterocycles. This process affords novel complex polycyclic scaffolds in moderate to good yields from readily available acyclic precursors with excellent chemo-, regio-, and diastereoselectivity. The power of this strategy has been demonstrated by the rapid synthesis of 40 highly functionalized polyheterocycles bearing indole, pyrrole, (benzo)furan, (benzo)thiophene, pyrazole, and electron-rich arene groups in two operational steps.

Enantiodivergent Combination of Natural Product Scaffolds Enabled by Catalytic Enantioselective Cycloaddition

An efficient strategy has been established for the enantiodivergent synthesis of natural product inspired compounds embodying both tropane and pyrrolidine natural product fragments. This strategy includes the enantioselective kinetic resolution of racemic tropanes by means of a copper(I)-catalyzed [3+2] cycloaddition and allows the preparation of two enantiopure products in a one-pot reaction in high yield and with high diastereo- and enantioselectivity by using one chiral catalyst.

Highly stereoselective synthesis of natural-product-like hybrids by an organocatalytic/multicomponent reaction sequence

In an endeavor to provide an efficient route to natural product hybrids, described herein is an efficient, highly stereoselective, one-pot process comprising an organocatalytic conjugate addition of 1,3-dicarbonyls to α,β-unsaturated aldehydes followed by an intramolecular isocyanide-based multicomponent reaction. This approach enables the rapid assembly of complex natural product hybrids including up to four different molecular fragments, such as hydroquinolinone, chromene, piperidine, peptide, lipid, and glycoside moieties. The strategy combines the stereocontrol of organocatalysis with the diversity-generating character of multicomponent reactions, thus leading to structurally unique peptidomimetics integrating heterocyclic, lipidic, and sugar moieties.

Biology-oriented synthesis of benzopyrano[3,4-c]pyrrolidines

A natural product inspired synthesis of 6,6,5-tricyclic compounds via a silver(I)-catalyzed formal 1,3-dipolar cycloaddition of coumarins with α-iminoesters was developed. The reaction proceeds in a stepwise reaction course under formation of the trans-substituted diastereomer with respect to the 1,3-dipole and shows a broad substrate scope.

Biology-oriented synthesis of a withanolide-inspired compound collection reveals novel modulators of hedgehog signaling

Biology-oriented synthesis employs the structural information encoded in complex natural products to guide the synthesis of compound collections enriched in bioactivity. The trans-hydrindane dehydro-δ-lactone motif defines the characteristic scaffold of the steroid-like withanolides, a plant-derived natural product class with a diverse pattern of bioactivity. A withanolide-inspired compound collection was synthesized by making use of three key intermediates that contain this characteristic framework derivatized with different reactive functional groups. Biological evaluation of the compound collection in cell-based assays that monitored biological signal-transduction processes revealed a novel class of Hedgehog signaling inhibitors that target the protein Smoothened.

Divergent solid-phase synthesis of natural product-inspired bipartite cyclodepsipeptides: total synthesis of seragamide A

Macrocyclic natural products (NPs) and analogues thereof often show high affinity, selectivity, and metabolic stability, and methods for the synthesis of NP-like macrocycle collections are of major current interest. We report an efficient solid-phase/cyclorelease method for the synthesis of a collection of macrocyclic depsipeptides with bipartite peptide/polyketide structure inspired by the very potent F-actin stabilizing depsipeptides of the jasplakinolide/geodiamolide class. The method includes the assembly of an acyclic precursor chain on a polymeric carrier, terminated by olefins that constitute complementary fragments of the polyketide section and cyclization by means of a relay-ring-closing metathesis (RRCM). The method was validated in the first total synthesis of the actin-stabilizing cyclodepsipeptide seragamide A and the synthesis of a collection of structurally diverse bipartite depsipeptides.

Synthesis of a natural product-like compound collection through oxidative cleavage and cyclization of linear peptides

Massive efforts in molecular library synthesis have strived for the development of synthesis methodology which systematically delivers natural product-like compounds of high spatial complexity. Herein, we present a conceptually simple approach that builds on the power of solid-phase peptide synthesis to assemble precursor peptides (oligomers) designed to undergo oxidative cascade reactions. By harnessing the structural side-chain diversity and inherent stereochemical features offered by readily available amino acids (monomers), a proof-of-concept collection of 54 skeletally and stereochemically diverse compounds was generated, and selected compounds were elaborated into isoform-selective metalloprotease inhibitors.

A trifluorinated thiazoline scaffold leading to pro-apoptotic agents targeting prohibitins

A new class of small molecules, with an unprecedented trifluorothiazoline scaffold, were synthesized and their pro-apoptotic activity was evaluated. With an EC50 in the low micromolar range, these compounds proved to be potent inducers of apoptosis in a broad spectrum of tumor cell lines, regardless of the functional status of p53. Fast structure-activity relationship studies allowed the preparation of the strongest apoptosis-inducing candidate. Using a high performance affinity purification approach, we identified prohibitins 1 and 2, key proteins involved in the maintenance of cell viability, as the targets for these compounds.

Catalytic enantioselective synthesis of functionalized tropanes reveals novel inhibitors of hedgehog signaling

Dipolar cycloaddition: A highly efficient copper(I)-catalyzed enantioselective [3+2] cycloaddition reaction of 1,3-fused cyclic azomethine ylides and nitroalkenes has been developed. This method provides access to functionalized tropane scaffolds with several quaternary and tertiary stereocenters in a single step under mild reaction conditions.

Discovery of inhibitors of the Wnt and Hedgehog signaling pathways through the catalytic enantioselective synthesis of an iridoid-inspired compound collection

Cousins you can count on: An iridoid-inspired compound collection was synthesized efficiently by the resolution of cyclic enones in an asymmetric cycloaddition with azomethine ylides. The collection contained novel potent inhibitors of the Wnt and Hedgehog signaling pathways.