This study discusses the choice of different simplified models used in computations of electronic circular dichroism (ECD) spectra and other chiroptical characteristics used to determine the absolute configuration (AC) of the complex natural product sibiricumin A. Sections of molecules containing one chiral center with one near an aromatic group have large effects on the ECD spectra. Conversely, when the phenyl group is present on a substituent without a nonstereogenic center, removal of this section will have little effect on ECD spectra. However, these nonstereogenic-center-containing sections have large effects on calculated optical rotations (OR) values since the OR value is more sensitive to the geometries of sections in a molecule. In this study, the wrong AC of sibiricumin A was reassigned as (7R,8S,1'R,7'R,8'S)-11. Chirality 28:612–617, 2016. © 2016 Wiley Periodicals, Inc.

Three new phenyl ether derivatives, 3-hydroxy-5-(3-hydroxy-5-methylphenoxy)benzoic acid (1), 3,4-dihydroxy-5-(3-hydroxy-5-methylphenoxy)benzoic acid (2), 3-[3-hydroxy-5-(hydroxymethyl)phenoxy]-5-methylphenol (3), and three known compounds 4–6 were obtained from the fermentation broth of Aspergillus carneus HQ889708, which was isolated from sea water from South China Sea. The structures of compounds 1–3 were established on the basis of spectroscopic methods including ESI-MS and NMR. Compounds 4–6 were reported before as synthesized products, herein, they are reported from nature for the first time.

The allylation of aromatic and aliphatic aldehydes with allyltrichlorosilanes has been catalyzed with a new Lewis base organocatalyst, 1,1′-biscarboline N,N′-dioxide with high enantioselectivities of up to 99% for 4-methoxybenzaldehyde and 97% ee for cycloformaldehyde, respectively. In total, 13 heteroaryl and aliphatic aldehydes were tested.

From the whole plants of E. ritro L., the three new sesquiterpenoids (3α,4α,6α)-3,13-dihydroxyguaia-7(11),10(14)-dieno-12,6-lactone (1), (3α,4α,6α,11β)-3-hydroxyguai-1(10)-eno-12,6-lactone (2), and (11α)-11,13-dihydroarglanilic acid methyl ester (=(4β,6α,11α)-4,6-dihydroxy-1-oxoeudesm-2-en-12-oic acid methyl ester; 3), together with eight known sesquiterpenoids, were isolated. Their structures were elucidated through analysis of spectroscopic data including extensive 2D-NMR.

A trinorsesquiterpene, 1, and its possible precursor sesquiterpene 2 were obtained from the Tibetan folk medicine Pulicaria insignis (Ming⋅chen⋅serpo). Their structures were elucidated on the basis of spectral methods including 2D-NMR. The trinorsesquiterpene skeleton of 1 is the second example of this type of structure found in a plant, after a first compound of this type was isolated from bird's nest fungi (Cyanthus bulleri).

The configuration of concentricolide was assigned as (S). The configuration of its three analogs, which have anti-HIV-1 activity, were predicted by optical rotation values obtained by the B3LYP/aug-cc-pVDZ//B3LYP/6-31+G(d) and B3LYP/aug-cc-pVDZ//MP2/6-311+G(d) methods. The two methods predict very close optical rotation magnitudes for all three chiral analogs of concentricolide. The two methods were applied in optical rotation predictions for seven other concentricolide analogs. Circular dichroism calculations were performed for four of the seven analogs at the B3LYP/aug-cc-pVDZ level.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Two new C₂₀-diterpenoid alkaloids named naviculine A (1) and naviculine B (2), were isolated from Aconitum naviculareStapf. Their structures were established by spectral methods, especially 2D-NMR spectra (¹H,¹H-COSY, HMQC, HMBC, and NOESY) and DFT methods (at the B3LYP/6-311++G(2d,p)//B3LYP/6-31G(d) level), respectively. They were assayed for their anti-HIV-1 activity.

Rubrifloradilactone C (4), a novel bioactive nortriterpenoid, along with four other nortriterpenoids (1–3, 5) were isolated from Schisandra rubriflora. The structure of 4 was determined by extensive NMR spectral analysis, computational evidence by using the GIAO method at the B3LYP/6–311++G(2d,p)//B3LYP/6–31G(d) levels, and X-ray analysis. DFT at the B3LYP/6–311+G(d,p) level was selected to clarify the key mechanistic steps in the formation of 1 and 4 through transition-state (TS) investigations. The effect of enzymes on the TS barriers was considered by using the polarized continuum model. Other possible products based on the new mechanism were predicted.