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Vibrational Circular Dichroism Similarity-Guided Absolute Configuration Determination of 11-Acyloxytremetones
| Content Provider | SAGE Publishing |
|---|---|
| Author | Muñoz, Marcelo A. Simirgiotis, Mario Joseph-Nathan, Pedro |
| Copyright Year | 2022 |
| Abstract | Although tremetone [5-acetyl-2-(1-methylvinyl)-2,3-dihydrobenzofuran] has only one stereogenic center, the absolute configuration (AC) determination of its naturally occurring 11-acyloxy derivatives 1 and 2 by vibrational circular dichroism (VCD) turned out to be difficult. Similarity-based comparison of the experimental VCD spectrum of 11-coumaryloxytremetone (1), isolated from Parastrephia quadrangularis, with spectra calculated using popular density functional theory (DFT) levels of theory, provided poor enantiomeric similarity indices (ESI), even when the p-coumaroyl ester group of 1 was replaced by the acetyl group in 2. In search for a better understanding of these results, IR-guided individual scaling factors (ISFs), recently introduced as part of the Vibrational Spectra Similarity and Analysis Tool (VISSAT) software, were used to correct DFT frequencies, while a VCD-guided conformational analysis was developed to explore conformational preferences. These studies showed that for both molecules 72% of the individual conformations gave ESI values in favor of the (R) enantiomer. Likewise, when conformer abundances were optimized to produce the best possible similarity for each enantiomer, the obtained ESI values were always larger for the (R) isomer than for the (S) isomer. These results point toward the (R) AC in both compounds and highlight the incorrect conformer abundance prediction by DFT calculations as the potential source of the initial difficulties. In addition, the AC of 1 was independently verified using the Flack and Hooft parameters gained after a single-crystal x-ray diffraction (XRD) study. |
| Related Links | https://journals.sagepub.com/doi/pdf/10.1177/1934578X221095342?download=true |
| ISSN | 1934578X |
| Issue Number | 4 |
| Volume Number | 17 |
| Journal | Natural Product Communications (NPX) |
| e-ISSN | 15559475 |
| DOI | 10.1177/1934578X221095342 |
| Language | English |
| Publisher | Sage Publications CA |
| Publisher Date | 2022-04-26 |
| Publisher Place | Los Angeles |
| Access Restriction | Open |
| Rights Holder | © The Author(s) 2022 |
| Subject Keyword | Parastrephia species 11-acetyloxytremetone 11-coumaryloxytremetone single-crystal x-ray diffraction absolute configuration vibrational circular dichroism |
| Content Type | Text |
| Resource Type | Article |
| Subject | Plant Science Drug Discovery Pharmacology Complementary and Alternative Medicine |
