A polyamide column chromatography method using an aqueous ammonia mobile phase was developed for large-scale accumulation of water-soluble indoline amide glucosides from a medicinal plant, Portulaca oleracea. Ten new [oleraceins H, I, K, L, N, O, P, Q, R, S (1–10)] and four known [oleraceins A–D (11–14)] indoline amide glucosides were further purified and structurally characterized by various chromatographic and spectroscopic methods. The DPPH radical scavenging activities of oleraceins K (5) and L (6), with EC50 values of 15.30 and 16.13 μM, respectively, were twice that of a natural antioxidant, vitamin C; the EC50 values of the 12 other indoline amides, which ranged from 29.05 to 43.52 μM, were similar to that of vitamin C. Structure–activity relationships indicated that the DPPH radical scavenging activities of these indoline amides correlate with the numbers and positions of the phenolic hydroxy groups.

The mechanisms of Selectfluor-mediated Au-catalyzed intramolecular Csp3–Csp2 cross-coupling reaction involving direct aryl Csp2–H functionalization have been investigated theoretically. Several pathways involving the oxidation of alkylgold(I) (Cycle I), phosphine Au(I) precatalyst (Cycle II), gold(I) π–alkene complex (Cycle III) and arylgold(I) (Cycle IV) by Selectfluor, respectively, were examined. Our calculation results suggested the following: (1) Cycles I and II are preferred over Cycles III and IV, and the reaction would undergo the energy favored pathways (Cycles I and II), which is further confirmed by stereochemical analysis; (2) Cycle I is competitive with Cycle II, and the rate-determining steps of these two cycles are oxidation of Au(I) species by Selectfluor; (3) water has been found to participate in the catalytic reaction and decrease the activation energy barrier of the reductive elimination.

The selective fluorination of aromatic compounds with Selectfluor has been studied theoretically. The structural and energetic features of π complexes of substituted benzenes with Selectfluor are investigated, and the fluorine bond (F⋯π) has been found to make an important contribution to the stabilization of the π complexes. Our calculations indicate that the SET mechanism, which involves one electron transfer from the aromatic substrate (D) to Selectfluor (A), is preferred over the SN2 mechanism. The analysis of the minimum energy path (MEP) suggests that the DABCO moiety of Selectfluor seems to take an active role in the fluorination of aromatic compounds with Selectfluor. In addition, a two-state model analysis, as well as the characteristics of avoiding crossing between the DA and D+A− states of benzene/Selectfluor are addressed to obtain deep insight into the features of the SET mechanism.

Peniciketals A–C (1–3), three new spiroketals with a benzo-fused 2,8-dioxabicyclo[3.3.1]nonane moiety, were isolated from the saline soil derived fungus Penicillium raistrichii. Their structures including absolute configurations were established by NMR, X-ray diffraction, and ECD calculations. Their cytotoxicities were tested against A549, HL-60, and K562 cell lines, and 1–3 showed the selective effects on HL-60 cells with IC50 values of 3.2, 6.7, and 4.5 μM, respectively.

Inherently chiral biscalixarenes with hetero-cavities were synthesized by a covalent assembly of p-tert-butylcalix[5]arene with a 1,3-substituted calix[4]arene via 1,3-alkylation reaction and subsequent desymmetrization. The racemates were resolved by chiral HPLC method. 1H NMR spectra, VT-NMR spectra, and theoretical calculations support that the calix[5]arene subunit of the inherently chiral calix[4][5]arene ester adopts a cone-in conformation, with the aromatic ring bearing the CH2CO2Et group tilting inward the calix[5]arene cavity. By contrast, such a cone-in structural feature of the calix[5]arene subunit disappears for the corresponding inherently chiral calix[4][5]arene carboxylic acid, due to the intramolecular hydrogen bonding between the carboxyl group and an ethereal oxygen of the glycolic chain.

Computational studies to determine the origin of enantioselectivity in the (1R,2R)-1,2-diphenylethane-1,2-diamine (DEPN)–Brønsted acid catalyzed epoxidation of 2-cyclohexen-1-one have been performed using density functional theory. Transition states for conjugate addition and ring closure steps of the epoxidations catalyzed by three different catalyst systems were characterized. Our calculations show that the Csp2H⋯O H-bond interaction between the benzene ring of the catalyst and H2O is mainly responsible for the chiral discrimination observed. The Brønsted acid counterion plays a very important role in ensuring high enantioselectivity by improving the rigidity of the transition state structures to allow the efficient formation of the Csp2H⋯O H-bond. Moreover, we explain why these two diamine catalysts (1S,2S)-DACH and (1R,2R)-DPEN display consistent enantioselectivities in the catalytic epoxidation of 2-cyclohexen-1-one when combining with three different cocatalysts; achiral TFA, and chiral (R)- and (S)-TRIP.

The asymmetric epoxidation of 2-cyclohexen-1-one with aqueous H2O2 as oxidant, 1,2-diaminocyclohexane as catalyst, and a Brønsted acid trifluoroacetic acid (TFA) as cocatalyst has been studied by performing density functional theory calculations. It is confirmed that the catalyzed epoxidation proceeds via sequential nucleophilic addition and ring-closure processes involving a ketiminium intermediate. Four possible pathways associated with two Z isomers and two E isomers of ketiminium have been explored in detail. Our calculation indicates that these four pathways have high barriers and a small energy gap between two more favorable R and S pathways. We have analyzed the effects of the TFA anion and H2O on the activity and enantioselectivity of catalytic epoxidation. It is found that the TFA anion acts as a counterion to stabilize the transition states of the catalytic epoxidation by hydrogen–bond acceptance, leading to decreases in the barriers of the nucleophilic addition and ring-closure processes. The most significant decrease occurred in the ring-closure step of the Z-R-pathway, resulting in H-bond-induced enantioselectivity. Our calculations also show that water cooperates with TFA to further increase the reaction rate significantly.

A practical and mild metal-free oxidative C–H functionalization of N-carbamoyl tetrahydro-β-carbolines has been reported. This reaction has excellent functional group tolerance, and exhibits a broad range of potassium trifluoroborate components, allowing for the facile C–H functionalization of electronically varied N-carbamoyl THCs in high efficiency with excellent regioselectivity.