The structural and functional characterization of natural products is vastly outpaced by the bioinformatic identification of biosynthetic gene clusters (BGCs) that encode such molecules. Uniting our knowledge of bioinformatics and enzymology to predict and synthetically access natural products is an effective platform for investigating cryptic/silent BGCs. We report the identification, biosynthesis, and total synthesis of a minimalistic class of ribosomally synthesized and post-translationally modified peptides (RiPPs) with the responsible BGCs encoding a subset of enzymes known from thiopeptide biosynthesis. On the basis of the BGC content, these RiPPs were predicted to undergo enzymatic dehydration of serine followed by [4+2]-cycloaddition to produce a trisubstituted, pyridine-based macrocycle. These RiPPs, termed “pyritides”, thus contain the same six-membered, nitrogenous heterocycle that defines the thiopeptide RiPP class but lack the ubiquitous thiazole/thiazoline heterocycles, suggesting that thiopeptides should be reclassified as a more elaborate subclass of the pyritides. One pyritide product was obtained using an 11-step synthesis, and the structure verified by an orthogonal chemoenzymatic route using the precursor peptide and cognate pyridine synthase. This work exemplifies complementary bioinformatics, enzymology, and synthesis to characterize a minimalistic yet structurally intriguing scaffold that, unlike most thiopeptides, lacks growth-suppressive activity toward Gram-positive bacteria.

Ap rotocol for palladium-catalyzed dearomative functionalization of simple,nonactivated arenes with Grignard reagents has been established. This one-pot method features avisible-light-mediated [4+ +2] cycloaddition between an arene and an arenophile,and subsequent palladium-catalyzed allylic substitution of the resulting cycloadduct with aG rignard reagent. Av ariety of arenes and Grignard reagents can participate in this process,f orming carboaminated products with exclusive syn-1,4-selectivity.M oreover,t he dearomatized products are amenable to further elaborations,p roviding functionalizeda licyclic motifs and pharmacophores.F or example,n aphthalene was converted into sertraline,o ne of the most prescribed antidepressants,i no nly four operations. Finally,t his process could also be conducted in an enantioselective fashion, as demonstrated with the desymmetrization of naphthalene.

This report details a search for alternative strains that produce the diterpenoid sphaeropsidin A (SphA) among A. candidus strains from the USDA Northern Regional Research Laboratories Culture Collection. We identified two strains that produced SphA using a limited set of test media. An initial scaled-up fermentation of NRRL 313 and isolation effort led to the procurement of sufficient quantities of SphA to prepare five semi-synthetic analogues (1-5) and evaluate their anticancer effects against glioblastoma cells D423 and Gli56 grown in 2D and 3D cultures. Although, the effectiveness of the synthetic analogues varied depending on the cell line and the type of cell culture, compound 5, bearing an aromatic ring at C16, displayed a stronger toxicity towards both D423 and Gli56 cell lines in 2D cultures and D423 spheroids in 3D culture than either SphA or compounds 1-4.

A protocol for palladium‐catalyzed dearomative functionalization of simple, nonactivated arenes with Grignard reagents has been established. This one‐pot method features a visible‐light‐mediated [4+2] cycloaddition between an arene and an arenophile, and subsequent palladium‐catalyzed allylic substitution of the resulting cycloadduct with a Grignard reagent. A variety of arenes and Grignard reagents can participate in this process, forming carboaminated products with exclusive syn‐1,4‐selectivity. Moreover, the dearomatized products are amenable to further elaborations, providing functionalized alicyclic motifs and pharmacophores. For example, naphthalene was converted into sertraline, one of the most prescribed antidepressants, in only four operations. Finally, this process could also be conducted in an enantioselective fashion, as demonstrated with the desymmetrization of naphthalene.

<p>Owing to advances in genomic sequencing and bioinformatics, the breadth of natural product biosynthetic gene clusters (BGCs) has meteorically risen. This remains true for ribosomally synthesized and post-translationally modified peptides (RiPPs), where the rate of bioinformatically identifying clusters vastly outpaces characterization efforts. Uniting bioinformatics and enzymological knowledge to predict the chemical product(s) of a RiPP BGC with total chemical synthesis to obtain the natural compound is an effective platform for investigating cryptic gene clusters. Herein, we report the bioinformatic identification of a biosynthetically divergent class of RiPP bearing a subset of enzymes involved in thiopeptide biosynthesis. These natural products were predicted based on BGC architecture to undergo a formal, enzymatic [4+2]-cycloaddition with subsequent elimination of the leader peptide and water to produce a tri-substituted pyridine-based macrocycle. Bearing a pyridine similar to thiopeptides but lacking the ubiquitous thiazole heterocycles, these new RiPPs were termed pyritides. One of the predicted natural products was chemically synthesized using an 11-step synthesis. This structure was verified to be chemically identical by an orthogonal chemoenzymatic synthesis utilizing the precursor peptide and the cognate [4+2]-cycloaddition enzyme. The chemoenzymatic platform was used to synthesize a second in-cluster pyritide product as well as analogs from other bioinformatically identified pyritide BGCs. This work exemplifies complementary bioinformatic, enzymological, and synthetic techniques to characterize a structurally distinct class of RiPP natural product.</p>