The imidato-alkenyllithium route for the synthesis of the isoquinocycline-pyrrolopyrrole substructure

A New Micromonospora Strain with Antibiotic Activity Isolated from the Microbiome of a Mid-Atlantic Deep-Sea Sponge

To tackle the growing problem of antibiotic resistance, it is essential to identify new bioactive compounds that are effective against resistant microbes and safe to use. Natural products and their derivatives are, and will continue to be, an important source of these molecules. Sea sponges harbour a diverse microbiome that co-exists with the sponge, and these bacterial communities produce a rich array of bioactive metabolites for protection and resource competition. For these reasons, the sponge microbiota constitutes a potential source of clinically relevant natural products. To date, efforts in bioprospecting for these compounds have focused predominantly on sponge specimens isolated from shallow water, with much still to be learned about samples from the deep sea. Here we report the isolation of a new Micromonospora strain, designated 28ISP2-46^T, recovered from the microbiome of a mid-Atlantic deep-sea sponge. Whole-genome sequencing reveals the capacity of this bacterium to produce a diverse array of natural products, including kosinostatin and isoquinocycline B, which exhibit both antibiotic and antitumour properties. Both compounds were isolated from 28ISP2-46^T fermentation broths and were found to be effective against a plethora of multidrug-resistant clinical isolates. This study suggests that the marine production of isoquinocyclines may be more widespread than previously supposed and demonstrates the value of targeting the deep-sea sponge microbiome as a source of novel microbial life with exploitable biosynthetic potential.

A Stereoselective, Multicomponent Catalytic Carbonylative Approach to a New Class of α,β-Unsaturated γ-Lactam Derivatives

We report a stereoselective, multicomponent catalytic carbonylative approach to a new class of α,β-unsaturated γ-lactam derivatives with potential biological activity, that are, alkyl (Z)-2-(2-oxopyrrolidin-3-ylidene)acetates. Our method is based on the catalytic assembly of readily available building blocks, namely, homopropargylic amines, carbon monoxide, an alcohol, and oxygen (from air). These simple substrates are efficiently activated in ordered sequence under the action of a very simple catalytic system, consisting of PdI2 in conjunction with KI to give the γ-lactam products in 47–85% yields. Carbonylation reactions are carried out at 100 °C for 2–5 h under 40 atm of a 4:1 mixture of CO‒air, with 0.5–5 mol% of PdI2 and 5–50 mol% of KI.

Unconventional origin and hybrid system for construction of pyrrolopyrrole moiety in kosinostatin biosynthesis

Kosinostatin (KST), an antitumor antibiotic, features a pyrrolopyrrole moiety spirally jointed to a five-membered ring of an anthraquinone framework glycosylated with a γ-branched octose. By a combination of in silico analysis, genetic characterization, biochemical assay, and precursor feeding experiments, a biosynthetic pathway for KST was proposed, which revealed (1) the pyrrolopyrrole moiety originates from nicotinic acid and ribose, (2) the bicyclic amidine is constructed by a process similar to the tryptophan biosynthetic pathway, and (3) a discrete adenylation enzyme and a peptidyl carrier protein (PCP) are responsible for producing a PCP-tethered building block parallel to type II polyketide synthase (PKS) rather than for the PKS priming step by providing the starter unit. These findings provide an opportunity to further explore the inexplicable enzymatic logic that governs the formation of pyrrolopyrrole moiety and the spirocyclic skeleton.