Bioinspired Total Synthesis and Stereochemical Revision of the Fungal Metabolite Pestalospirane B

Polyketone metabolites isolated from Rhodiola tibetica endohytic fungus Alternaria sp. HJT-Y7 and their SARS-CoV-2 virus inhibitory activitives

Six new polyketone metabolites, compounds (1–6) and seven known polyketone compounds (7–13) were isolated from Rhodiola tibetica endophytic fungus Alternaria sp. The structural elucidation of five new polyketone metabolites were elucidated on the basis of spectroscopic including 2D NMR and HRMS and spectrometric analysis. Inhibition rate evaluation revealed that compounds 1(EC₅₀ = 0.02 mM), 3(EC₅₀ = 0.3 mM), 6(EC₅₀ = 0.07 mM), 8(EC₅₀ = 0.1 mM) and 9(EC₅₀ = 0.04 mM) had inhibitory effect on the SARS-CoV-2 virus.

Scalable Biomimetic Syntheses of Paeciloketal B, 1-epi-Paeciloketal B, and Bysspectin A

The first total synthesis of the benzannulated 5,5-spiroketal natural products paeciloketal B and 1-epi-paeciloketal B has been achieved in 10 linear steps employing a biomimetic spiroketalization. This approach also furnished the related natural product bysspectin A from the same putative biosynthetic precursor as the paeciloketals. Alternatively, bysspectin A could be accessed in only six steps using an improved route. This scalable and efficient synthesis affords insight into the biosynthesis of these natural products in nature.

Cytotoxic Polyketides from the Marine Sponge-Derived Fungus Pestalotiopsis heterocornis XWS03F09

Four new compounds, including two new polyketides, heterocornols M and N (1, 2), and a pair of epimers, heterocornols O and P (3, 4), were isolated from the fermentation broth of the marine sponge-derived fungus Pestalotiopsis heterocornis XWS03F09, together with three known compounds (5-7). The new chemical structures were established on the basis of a spectroscopic analysis, optical rotation, experimental and calculated electronic circular dichroism (ECD). All of the compounds (1-7) were evaluated for their cytotoxic activities, and heterocornols M-P (1-4) exhibited cytotoxicities against four human cancer cell lines with IC₅₀ values of 20.4-94.2 μM.

Computational prediction of chiroptical properties in structure elucidation of natural products

Covering: up to 2019This review covers the current status of the quantum mechanical prediction of chiroptical properties, such as electronic CD and optical rotation, as needed for stereochemical assignments in new natural products. The reliability of the prediction of chiroptical properties is steadily increasing, with a parallel decrease in the required computational resources. Now, quantum mechanical calculations for a medium-sized natural product can be reliably performed by natural product chemists on a mainstream PC. This review is aimed to guide natural product chemists through the numerous steps involved in such calculations. Through a concise, but comprehensive, discussion of the current computational practice, enriched by a few illustrative examples, this review provides readers with the theoretical background and practical knowledge needed to select the most appropriate parameters for performing the calculations, to anticipate possible problems, and to critically evaluate the reliability of their computational results. Common reasons for mistakes are also discussed; in particular, the importance of the correct evaluation of conformational ensembles of flexible molecules (an aspect often overlooked in current research) is stressed.

Benzannulated spiroketal natural products: isolation, biological activity, biosynthesis, and total synthesis

A review discussing the isolation, biological activity, biosynthesis, and total synthesis of naturally occurring benzannulated spiroketals.

Structural Diversity and Biological Activities of Novel Secondary Metabolites from Endophytes

Exploration of structurally novel natural products greatly facilitates the discovery of biologically active pharmacophores that are biologically validated starting points for the development of new drugs. Endophytes that colonize the internal tissues of plant species, have been proven to produce a large number of structurally diverse secondary metabolites. These molecules exhibit remarkable biological activities, including antimicrobial, anticancer, anti-inflammatory and antiviral properties, to name but a few. This review surveys the structurally diverse natural products with new carbon skeletons, unusual ring systems, or rare structural moieties that have been isolated from endophytes between 1996 and 2016. It covers their structures and bioactivities. Biosynthesis and/or total syntheses of some important compounds are also highlighted. Some novel secondary metabolites with marked biological activities might deserve more attention from chemists and biologists in further studies.

Recent progress in the isolation, bioactivity, biosynthesis, and total synthesis of natural spiroketals

The isolation, bioactivity, biosynthesis, and total synthesis of natural spiroketals from 2011 to July 2017 have been summarized in this review.