Synthesis of muscothiazoles A and B: Critical role of methyl group substitution in RCM-based syntheses of macrocycles

Synthesis, bioactivity and mode of action of 5A 5B 6C tricyclic spirolactones as novel antiviral lead compounds

BACKGROUND

Plant viral diseases cause tremendous decreases in yield and quality. Natural polycyclic compounds such as those containing carbocycles are often very important lead compounds for drug and pesticide development. Tricyclic spiranoid lactones with 5_A 5_B 6_C -ring fusion topologies possess various bioactivities. In this study, 33 new 5_A 5_B 6_C tricyclic spirolactones were rationally designed, synthesized, characterized and evaluated for antiviral activities.

RESULT

These compounds showed no apparent toxicity against Italian honeybees up to 2.73 µg bee^-1 . Spirolactones 14, 16, 19, 23 and 28 at a concentration of 100 µg mL^-1 inactivated 90% of tobacco mosaic virus (TMV) infection, making these compounds much more potent than the positive controls. Significantly, compound 19 displayed the best inactivation activity causing inhibition of up to 98%.

CONCLUSION

The results of the bioassays and QSAR studies indicated that the carbon-containing cyclic moiety was the antiviral pharmacophore, and derivative 19, which showed the best inactivation activity, could emerge as a potential antiviral agent against TMV. In vitro capsid protein (CP) assembly and TMV assembly inhibition determinations indicated that these compounds induced crosslinking in the TMV and prevented its uncoating, which was a putative new mode of action for TMV inactivation. © 2018 Society of Chemical Industry.

Exploiting quadrupolar interactions in the synthesis of the macrocyclic portion of longithorone C

2,3,4,5,6-Pentafluorobenzyl and 3,5-bistrifluoromethylbenzyl ester auxiliaries can enable difficult macrocyclizations to afford rigid all-carbon paracyclophanes. The effectiveness of these auxiliaries has been demonstrated in preparing the carbon skeleton of the macrocyclic natural product longithorone C.

Towards novel difluorinated sugar mimetics; syntheses and conformational analyses of highly-functionalised difluorinated cyclooctenones

Highly-functionalised difluorinated cyclooctenones were synthesised from trifluoroethanol using either metallated difluoroenol acetal or carbamate chemistry, followed by a [2,3]-Wittig rearrangement or aldol reaction. Efficient RCM reactions afforded the title compounds which showed rather restricted fluxional behaviour by VT (19)F NMR. Topological characterisation by molecular modelling and NOESY/ROESY experiments offered a number of challenges, but allowed the identification of two favoured boat-chair conformers which interconverted by pseudorotation with relatively large activation barriers.