The present work describes the isolation of (+)-(8S)-10-benzoyloxy-6-hydroxy-8,9-epoxythimol isobutyrate (7) from the leaves of Ageratina glabrata, and areolal (13), and 10-cinnamoyloxy-8,9- epoxythymol isobutyrate (14) from the roots of Piptothrix areolare, as well as, 7-acetoxy-10- cinnamoyloxy-8,9-epoxythymol isobutyrate (15), 10-cinnamoyloxy-7-hidroxy-8,9-epoxythymol isobutyrate (16), (8S)-7-acetoxy-10-cinnamoyloxy-6-hydroxy-8,9-epoxythymol isobutyrate (17), and (8S)-10-cinnamoyloxy-8,9-epoxy-6-hydroxy-7-northymol isobutyrate (18), from the flowers of P. areolare. The enantiomeric purity of the above compounds was determined by 1H NMRBINOL measurements, where 13-16 as scalemic mixtures were evidenced, while 7, 17 and 18 are enantiomerically pure compounds. After, Absolute Configuration (AC) determination studies for 14-18 were achieved by ECD measurements and results were compared with that ECD spectrum from 13, whose AC was known. Results revealed the 8S- configuration for 17 and 18, as well as for the major enantiomer in 14-16. In addition, a methodology to obtain theoretical spectra of ECD using TD-DFT calculations for AC studies in epoxythymol derivatives is proposed.
En el presente trabajo se describe la obtención del derivado de timol isobutirato de (+)- (8S)-10-benzoiloxi-6-hidroxi-8,9-epoxitimilo (7), aislado de las hojas de Ageratina glabrata y de los derivados areolal (13), isobutirato de 10-cinamoiloxi-8,9-epoxitimilo (14), isobutirato de 7- acetoxi-10-cinamoiloxi-8,9-epoxitimilo (15), isobutirato de 10-cinamoiloxi-7-hidroxi-8,9- epoxitimilo (16), isobutirato de (8S)-7-acetoxi-10-cinamoiloxi-6-hidroxi-8,9-epoxitimilo (17) e isobutirato de (8S)-10-cinamoiloxi-8,9-epoxi-6-hidroxi-7-nortimilo (18), aislados de las flores y raíces de Piptothrix areolare. Las purezas enantioméricas de los compuestos se determinaron mediante mediciones de RMN-BINOL, obteniendo a 13-16 como mezclas escalémicas mientras que, 7, 17 y 18 fueron enantioméricamente puros. En un trabajo previo de nuestro grupo de investigación se determinó la configuración absoluta de 13 a partir de DCV asignándola como (S). La obtención de los espectros de DCE de los epoxitimoles 14-18 y su comparación con los adquiridos para 13 permitieron determinar su configuración absoluta. Adicionalmente, se propone una metodología para la obtención de espectros teóricos de DCE mediante teoría de funcionales de la densidad dependiente del tiempo (TD-DFT).
