TDDFT CD Calculations Research Articles

Cis-Clerodane diterpenoids from the Chinese liverwort Scapania parva Steph.

Three undescribed cis-clerodane lactones, scapanialides A–C (1–3), and a new cis-clerodane furano-diterpenoid, scaparvin F (4), were isolated from the Chinese liverwort Scapania parva Steph. Scapanialide B (2) is the first cis-clerodane diterpenoid with a bicyclo[5.4.0]undecane skeleton from liverworts. Their structures including the absolute configurations were determined by extensive analysis of multidimensional NMR spectroscopy and TDDFT CD calculations, together with crystal X-ray diffraction measurements. The cytotoxicity of compounds 1–4 was preliminary tested against the Hela and MCF-7 cell lines.

Sorbiterrin A, a novel sorbicillin derivative with cholinesterase inhibition activity from the marine-derived fungus Penicillium terrestre

A novel sorbicillinoid named sorbiterrin A ( 1), possessing an unprecedented skeleton was isolated from a marine sediment derived fungus Penicillium terrestre. The structure including absolute stereochemistries was elucidated by analysis of NMR, MS data and TDDFT CD calculations. Sorbiterrin A showed moderate acetylcholinesterase (AChE) inhibitory effect with IC 50 25 μg/mL.

Chloctanspirones A and B, novel chlorinated polyketides with an unprecedented skeleton, from marine sediment derived fungus Penicillium terrestre

Two novel chlorinated sorbicillinoids named chloctanspirones A ( 1) and B ( 2), possessing an unprecedented bicyclo[2.2.2]octane-2-spiro cyclohexane skeleton, together with their quasi-precursors terrestrols K ( 3) and L ( 4), two additional new chlorinated compounds, were isolated from a marine sediment derived fungus Penicillium terrestre. Their structures including absolute stereochemistries were elucidated by analysis of NMR, MS data, and TDDFT CD calculations. The cytotoxic effects of 1– 4 were preliminarily evaluated in HL-60 and A-549 cells. Compound 1 was active against both HL-60 and A-549 cells with IC 50s 9.2 and 39.7 μM, respectively, while 2 showed weaker activity only against HL-60 cells (IC 50 37.8 μM).

Synthesis of Hydroxynaphthyl-Substituted α-Amino Acid Derivatives via a Modified Mannich Reaction

An efficient one-pot synthesis of hydroxynaphthyl-substitutedglycine derivatives from 2- or 1-naphthol, glyoxylic acid, and benzylcarbamate via a modified Mannich reaction is described. The enantiomerswere successfully separated on analytical and semipreparative HPLCcolumns. Their absolute configurations were determined by CD analysissupported by TDDFT CD calculations.

Palmarumycins BG1−BG7 and Preussomerin BG1: Establishment of Their Absolute Configurations Using Theoretical Calculations of Electronic Circular Dichroism Spectra

Palmarumycins BG1-BG7 (1-7), seven new compounds related to palmarumycins, were isolated from the aerial parts of Bruguiera gymnorrhiza as well as a new preussomerin derivative BG1 (8). The structures of these compounds were determined mainly by the analysis of their NMR and MS data, and their relative configurations were assigned on the basis of their (3)J(H,H) coupling constants. Compounds 4 and 7 have a sulfate group that is unprecedented among members of spirodioxynaphthalene-type natural products. The absolute configurations of 1-8 were determined by TDDFT CD calculations of the solution conformers. Compound 5 displayed inhibitory activity against HL 60 and MCF-7 cell lines.

Viburspiran, an Antifungal Member of the Octadride Class of Maleic Anhydride Natural Products

AbstractViburspiran (8), a structurally new member of the maleic anhydride natural products, was isolated, along with seven known compounds 9–15, from the fungal endophyte Cryptosporiopsis sp. The structure of the new compound was elucidated by spectroscopic methods and confirmed by single‐crystal X‐ray analysis. The absolute configuration was established by TDDFT CD calculations by using the solid‐state structure for input geometry. Viburspiran (8) is the first representative of a new class of eight‐membered maleic anhydride natural products, named octadrides and exhibited antifungal activity against Botrytis cinerea and Microbotryum violaceum.

Labdane diterpenoids and highly methoxylated bibenzyls from the liverwort Frullania inouei

Four undescribed labdane diterpenoids, 1,2-dehydro-3,7-dioxo-manoyl oxide ( 1), 1,2-dehydro-7 β-hydroxy-3-oxo-manoyl oxide ( 2), 3,7-dioxo-manoyl oxide ( 3), and 3 β-hydroxy-7-oxo-manoyl oxide ( 4) together with three known diterpenoids ( 5– 7) and four highly methoxylated bibenzyls ( 8– 11) were isolated from the liverwort Frullania inouei. The absolute structures of 1– 4 were established by combined analysis of NMR data, CD data coupled with TDDFT CD calculations, and single-crystal X-ray diffraction measurement. Cytotoxicity tests to human tumor KB, KB/VCR, K562 or K562/A02 cells showed bibenzyls 8– 11 inhibited cell proliferation with ID 50 values ranging from 11.3 to 49.6 μM and overcame the multidrug resistance (MDR) with the reversal fold (RF) values ranging from 3.19 to 10.91 (5 μM) for vincristine-resistant KB/VCR and RF values from 4.40 to 8.26 (5 μM) for adriamycin-resistant K562/A02 cells, respectively. However, none of the diterpenoids were found to be active (ID 50 > 50 μM).

Pseudoanguillosporin A and B: Two New Isochromans Isolated from the Endophytic Fungus Pseudoanguillospora sp.

AbstractTwo new isochromans named pseudoanguillosporin A (2a) and B (3), together with the known cephalochromin (1), were isolated from Pseudoanguillospora sp. The C‐2 absolute configuration of 2a and 3 was deduced from its CD spectrum by the isochroman helicity rule, supported by TDDFT CD calculations. The absolute configuration of the sec‐hydroxyl group of 3 was determined by the Mosher NMR method from the MPA esters of its methylated derivative. The axial chirality of 1 was assigned through exciton analysis of its CD spectrum and confirmed by ZINDO CD calculations. The metabolites showed broad antimicrobial activities.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Assignment of the absolute configuration of zwitterionic and neutral macropodumines by means of TDDFT CD calculations

Macropodumines B and C (1, 2) are fused pentacyclic alkaloids previously isolated from the Chinese medicinal plant Daphniphyllum macropodum. Macropodumine B (1) possesses an amazing structural feature of a cyclopentadienyl carbanion, stabilized as a zwitterion by an internal iminium cation, which was confirmed by X-ray diffraction analysis. On the basis of the X-ray geometry, the absolute configuration of 1 was determined by employing the solid-state CD/TDDFT approach. The absolute configuration of 2 was instead determined by using TDDFT CD calculations on DFT-optimized geometries, in comparison with CD spectra recorded in solution.

Antialactone: A New γ-Lactone from Antiaris Africana, and its Absolute Configuration Determined from TDDFT CD Calculations

Four compounds were isolated from the stem bark of Antiaris africana. One of them, a γ-lactone named antialactone (1a), is reported for the first time as a natural product. The structures were determined by comprehensive analyses of their 1D and 2D NMR spectra and EI MS data. The absolute configuration of antialactone acetate (1b) was established by TDDFT CD calculations and comparison with measured CD spectra. The remaining three known compounds were identified, by comparing their spectroscopic data with those reported in the literature, as lichenxanthone, β-sitosterol, and betulinic acid.

Absolute configuration of 1β,10β-epoxydesacetoxymatricarin isolated from Carthamus oxycantha by means of TDDFT CD calculations

The absolute configuration of 1β,10β-epoxydesacetoxymatricarin 1, a sesquiterpenoid isolated from Carthamus oxycantha, was established by TDDFT CD calculations in combination with single crystal X-ray analysis. Since the solid-state CD spectrum shows contributions from intermolecular interactions in the crystal, 1 represents a test case for our solid-state CD/TDDFT approach.

Synthesis, Optical Resolution, and Configurational Assignment of Novel Axially Chiral Quateraryls

A one-pot general synthesis of highly functionalized quateraryls through carbanion-induced, base-catalyzed ring transformation of 5,6-diaryl-2H-pyran-2-ones and core-substituted phenylacetones is delineated. These conversions were found to give diversely functionalized benzenes bearing peripheral aryl rings, some of which possess inherent atropisomerism. Exemplarily for one of the quateraryls, the optical resolution of the respective atropo-enantiomers by HPLC on a chiral phase and the assignment of their absolute axial configurations succeeded by LC-CD coupling in combination with semiempirical CNDO/S and TDDFT CD calculations. This synthetic approach offers-in a transition metal-free environment-high flexibility in the construction of quateraryls with the desired conformational freedom along the molecular axis, which may help in exploring and developing new potential ligands for asymmetric synthesis.

Circular dichroism of diglycosyl dichalcogenides in solution and solid state

Solution and solid-state CD spectra of nine peracetylated and deacetalyted diglycosyl disulfides were measured to study the relationship between the low-energy CD transitions (n1-->sigma*(S--S) and n2-->sigma*(S--S)) and helicity of the inherently chiral disulfide chromophore as perturbed by chiral carbohydrate moieties. The solid-state CD spectra were directly correlated with the reported X-ray structures of Ac4GlcSSGlcAc4 and Ac4GlcSSGalAc4, and the CD data revealed that all the disulfides have M helicity with C1--S--S--C1' dihedral angles -90 degrees < phi < 0 degrees both in solution and in the solid state. A TDDFT CD study was carried out on dimethyl diselenide which confirmed that the same quadrant rule is relevant between the signs of the low-energy CD transitions and the diselenide torsional angle as formulated previously for the disulfide chromophore. The CD spectra of Ac4GlcSeSeGlcAc4 measured in solution and in the solid state were correlated with its X-ray structure and reproduced well by TDDFT CD calculations performed on its tetra-O-acetyl derivative.