Efficient Total Synthesis of Racemic Bisabolane Sesquiterpenes Curcuphenol and Xanthorrhizol Starting from Substituted Acetophenones

Unlocking the antiviral arsenal: Structure-guided optimization of small-molecule inhibitors against RSV and hCoV-229E

Acute respiratory diseases in humans can be caused by various viral pathogens such as respiratory syncytial virus (RSV), human coronavirus 229E (hCoV-229E), and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). To prevent severe cases by an early treatment, one effective strategy is to inhibit viral infection at the entry stage of the replication cycle. However, there is a lack of efficient, FDA-approved small-molecule drugs targeting these pathogens. Previously, we identified two dual RSV/hCoV-229E small-molecule inhibitors with activity in the single-digit micromolar range. In this study, we focused on a structure-guided optimization approach of the more promising prototype addressing activity, cell viability, selectivity, solubility and metabolic stability. We present valuable insights into the structure-activity relationship (SAR), and report the discovery of a sub-micromolar RSV entry inhibitor, a dual RSV/CoV-229E inhibitor and a highly potent compound against hCoV-229E.

New Oxygenated Methoxy-p-Cymene Derivatives from Leopard's Bane (Doronicum columnae Ten., Asteraceae) Essential Oil: Synthesis Facilitating the Identification of Isomeric Minor Constituents in Complex Matrices

Species of the genus Doronicum are known for their pharmacological properties and essential oils, the chemical composition of which remains inadequately studied. In this work, GC-MS analysis, synthesis, and spectral techniques (UV, IR, MS, and NMR) were employed to identify 83 constituents in the essential oil from D. columnae roots, which accounted for 98.1% of the total GC-peak area. The major components were thymyl isobutyrate (32.8%) and thymyl 2-methylbutyrate (22.8%), while the minor constituents were methoxy-p-cymene derivatives. Six new natural products were identified through synthesis, GC co-injection experiments and spectral characterization, including esters (isobutyrate, 2-methylbutyrate, and/or isovalerate) of 2-methoxycuminol, 6-methoxythymol, and 6-hydroxythymyl methyl ether, as well as methyl 3-methoxycuminate. Their identification was made possible by synthesis efforts, as isolating pure compounds was impracticable because of their low abundance and the overall structural similarity within the highly complex mixture that was the essential oil.

A biomimetic approach towards phorone sesterterpenoids

We report an investigation towards a unified total synthesis of the Korean sponge derived sesterterpenoids, phorones A (1) and B (2), via a biomimetic strategy. This work has established a new synthetic strategy to the parent ansellane sesterterpenoid skeleton with unanticipated diversion to a biogenetically related pathway.

An entry to curcuphenol/elvirol core structures via a retro-Aldol reaction

Analogs of curcuphenol/elvirol, naturally occurring bisabolane sesquiterpenes, were prepared in six steps from alkyl-α-tetralones employing an aromatization reaction of cyclic dienone precursors and olefination of the key aldehyde intermediates. The in vitro antifungal activities of 6a, 6b, 6d, and 6g are also reported.

Facile Total Synthesis of Xanthorrhizol

A facile total synthesis of the bisabolane sesquiterpene, xanthorrhizol (1), has been achieved in 6 steps, in 48% overall yield. The starting material was 3-methoxy-4-methyl-phenoacetone (7), and a Claisen-Johnson rearrangement was used as the key step to construct the skeleton of the target molecule.