Absolute Configurations of Globosuxanthone A and Secondary Metabolites from Microdiplodia sp. – A Novel Solid‐State CD/TDDFT Approach

Abstract

Keywords: Fungal secondary metabolites / Microdiplodia sp. / Dihydroxanthenone / Single-crystal X-ray analysis / TDDFT CD calculations / Solid-state CDThe absolute configuration of a potent new antitumor dihydroxanthenone, globosuxanthone A (1), active against human solid tumor cell lines and isolated by Gunatilaka et al.from Chaetomium globosum Ames [1] and in this study from the endophytic fungus Microdiplodia sp., was established by a new methodology. In this new approach, the Cartesian coordinates of the X-ray data serve as input geometry for quan-

Circular dichroism of diglycosyl dichalcogenides in solution and solid state

“…Since its absolute configuration is known, the main purpose here is to test our solid-state TDDFT CD approach [25][26][27][28] on a compound containing the diselenide moiety, to which applications of TDDFT calculations are scarce (TDDFT calculations on selenium-containing compounds: refs 37, 38).…”

Experimental aspects of solid state circular dichroism

“…These can be used in ECD and VCD too: a few drops of a regular VCD solution of (2)-Camphor in CCl 4 were dispersed on the NaCl surface and solvent was dried out in a few minutes. The resulting VCD spectra (with mild baseline correction) is shown in Figure 2.…”

The prediction of the circular dichroism of the benzene chromophore: TDDFT calculations and sector rules

“…The situation is less problematical in the high energy region, where compounds 1-3 obey the sector rule available for 1 L a Cotton effect, and TDDFT calculations reproduce the observed spectra in terms of signs and relative intensity. It must be stressed that, in the most common application of TDDFT CD calculations for assigning absolute configurations, [5][6][7][8][9][10] one would logically focus on the most intense region of the spectrum (185-230 nm); in the current case, TDDFT results would unambiguously provide the correct answer for all compounds 1-4 considered. …”

“…3,4 As TDDFT CD calculations were made routinely available with commercial software, the comparison between experimental and TDDFT-computed CD spectra has become a popular tool for assigning absolute configurations. [5][6][7][8][9][10] Aromatic rings constitute the most common and important chromophores among organic molecules. The parent benzene chromophore, in particular, represents a crucial benchmark for the evaluation of the performance of computational techniques in the prediction of excitation energies of organic molecules.…”