Exploring Diversity through Dimerization in Natural Products by a Rational Tandem Mass-Based Molecular Network Strategy

DMSO enhances the biosynthesis of epoxyquinols in Pestalotiopsis sp. (strain IQ-011) and yields new [4 + 2] cycloaddition dimers

Pestalotiopsis sp. (strain IQ-011) produces cuautepestalorin (10), a 7,8-dihydrochromene-oxoisochromane adduct featuring a spiro-polycyclic (6/6/6/6/6/6) ring system. Additionally, it yields its proposed biosynthetic precursors: cytosporin M (1) and oxopestalochromane (11) when cultured under standard conditions (fermentation in solid media). Following an OSMAC approach guided by metabolomic studies (PCA and molecular networks), it was established that the epigenetic modulator DMSO dramatically increases the production of 1 up to 50 times according to feature-based molecular networking (FBMN) analysis, and triggers the production of other derivatives from the epoxyquinol family. Chemo-targeted isolation resulted in the discovery of four new compounds: 19-hydroxycytosporin M (2) and three [4 + 2] cycloaddition products: ent-eutyscoparol J (4), ent-pestaloquinol A (6) and ent-pestaloquinol B (8). The structures of all isolates were established based on spectroscopic, spectrometric, chiroptical, and X-ray diffraction analyses. This study demonstrates the potential of combining metabolomic tools with DMSO as an epigenetic modulator to enhance fungal metabolite diversity and highlights the importance of chiroptical methods for accurate compound identification.

Targeted discovery of clerodane diterpenoids from Tinospora sinensis as immunomodulatory agents

Under the guidance of MS/MS-based molecular networking, five new clerodane diterpenoid glucosides, tinosinesides R-V (1-5), along with 15 known diterpenoids (6-20), were isolated from the stems of Tinospora sinensis. Compound 1 represents the first example of diterpenoid bearing a thio sugar and compound 5 is the first 18,19-dinor-clerodane with cis-fused A/B ring. The structures of the new compounds were elucidated by spectroscopic means, and their absolute configurations were established on the basis of time-dependent density functional theory (TD-DFT) based electronic circular dichroism (ECD) calculation and chemical methods. Selected compounds were evaluated for their immunomodulatory effect and several compounds could enhance the proliferation of B lymphocytes. Preliminary mechanistic studies disclosed that 3 could promote B cell generation and inhibit B cell differentiation.

Regio- and Diastereoselective Radical Dimerization Reactions for the Construction of Benzo[f]isoindole Dimers

This study presents a novel approach for synthesizing benzo[f]isoindole dimers, which involves cascade cyclization and oxidative radical dimerization. Our method allows for the formation of up to five carbon-carbon bonds in a single reaction, exhibiting remarkable diastereoselectivity and regioselectivity. The mechanism and regioselectivity were investigated through a combination of experiments and calculations.