Absolute configurations of stink bug- and plant-produced sesquipiperitols via synthesis of all stereoisomers

Authors: Khrimian, Ashot; GUGGILAPU, SRAVANTHI - Nih, National Institutes Of Allergy And Infectious Diseases; Guzman, Filadelfo; BLASSIOLI-MORAES, MARIA CAROLINA - Embrapa; BORGES, MIGUEL - Embrapa

Submitted to: Journal of Natural Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2020
Publication Date: 7/10/2020
Citation: Khrimian, A., Guggilapu, S.D., Guzman, F., Blassioli-Moraes, M., Borges, M. 2020. Absolute configurations of stink bug- and plant-produced sesquipiperitols via synthesis of all stereoisomers. Journal of Natural Products. https://doi.org/10.1021/acs.jnatprod.0c00517.
DOI: https://doi.org/10.1021/acs.jnatprod.0c00517

Interpretive Summary: Sesquipiperitol is a chemical produced by several plants, in which its biological role is unknown. It has recently been identified as a rice stalk stink bug sex pheromone component and an intermediate in the biosynthesis of the harlequin bug pheromone. The the rice stalk stink bug is an important rice pest in Brazil with a high invasive potential in USA. The pheromones (or chemicals released by insects to trigger a response of the same species) have been successfully used in monitoring of different type of insect. The manuscript describes identification of absolute configurations, or exact stereo structures deferring by spatial arrangements of certain groups, of plant- and insect-produced compounds via syntheses of all eight stereo isomers of sesquipiperitol. The work is of interest to entomologists, organic chemists, and pest management dealing with invasive species.

Technical Abstract: Sesquipiperitol is a sesquiterpene alcohol, some stereoisomers of which were found in several plant species. The biological role of these compounds in plants and their absolute configurations were not disclosed. Recently, we found that 1S,6S,7R stereoisomer of sesquipiperitol was a key precursor in the biosynthesis of the harlequin bug, Murgantia histrionica, pheromone, which consists of two stereoisomeric zingiberenol oxides. In addition, Tibraca limbativentris stink bug was shown to produce two sesquipiperitol stereoisomers as minor components in their male-produced sex pheromone, the main constituents of which were zingiberenols. To determine absolute configurations of plant- and stink bug-produced sesquipiperitols, we undertook syntheses of all stereoisomers of these sesquiterpene alcohol. The syntheses were based on 1,10-bisaboladien-3-ols (aka zingiberenols) with known configurations at C-6 and C-7, oxidation of which provided sesquipiperitone precursors with retention of configurations of these stereogenic centers. The foremost challenge of the synthetic endeavor was the assignment of absolute configurations of secondary carbinol centers, which was resolved by NMR analyses of corresponding Mosher esters. Thus, the availability of all eight diastereomers allowed us to assign sesquipiperitols from Fitzroya cupressoides and Argyranthemum adauctum spp. jacobaeifolium plants 1S,6S,7R (16) and 1R,6R,7S (14) configurations, respectively. A chiral gas-chromatographic method was developed to determine 1S,6S,7R and 1R,6S,7R (15) configurations of T. limbativentris sesquipiperitol pheromone components.