Separation of five oligostilbenes from Vitis amurensis by flow‐rate gradient high‐performance counter‐current chromatography

A rapid and efficient high‐performance counter‐current chromatography (HPCCC) method was developed to separate five oligostilbenes from the roots of Vitis amurensis. An n‐hexane/ethyl acetate/methanol/water system (4:8:4:10, v/v/v/v) was selected as an optimal two‐phase solvent system of which the upper phase was used as the stationary phase and the lower phase was used as the mobile one. Partition coefficient values for the target compounds under these optimized conditions were 0.28 ( 1 , ampleosin A), 7.12 ( 2 , (+)‐g‐viniferin), 2.26 ( 3 , vitisin A), 5.38 ( 4 , wilsonol C), and 11.23 ( 5 , vitisin B). Flow‐rate gradient HPCCC (4 mL/min in 0–70 min, 8 mL/min in 70–250 min) was applied to isolate the target compounds in as high purity as possible within the shortest possible run time. Under these conditions, ampelopsin A (12.1 mg), (+)‐g‐viniferin (10.4 mg), vitisin A (2.8 mg), wilsonol C (3.2 mg), and vitisin B (37 mg) were isolated with >95% purity from 150 mg of enriched oligostilbene extract. Although the K_D of the last eluted compound, vitisin B (K_D = 11.23), was relatively large, it was eluted in 115–145 min using the two‐phase solvent system. This study shows that HPCCC is an efficient tool for the isolation and purification of natural products.     

FeCl3·6H2O oxidation of protected resveratrol for the synthesis of tetraarylfuran-type oligostilbenes

Several 8-8-coupled tetraarylfuran-type oligostilbenes were prepared through FeCl₃·6H₂O-catalyzed regioselective oxidative couplings of protected resveratrol precursors. The global deprotection of the coupling dimers in a one-pot reaction yielded (±)-pallidol instead of the targets (±)-restrytisol B and (±)-tricuspidatol A.     

Ultrasonic-assisted extraction and adsorption separation: Large-scale preparation of trans-ε-Viniferin,suffruficosol B and trans-Gnetin H for the first time

In this study, a Standard Operating Procedure (SOP) for the large-scale extraction, enrichment, and separation of suffruticosol B (SB), trans-ε-Viniferin (TV), trans-gnetin H (TG) from oil tree peony seeds shell (PSS) was successfully constructed. The ultrasonic-assisted extraction (UAE), macroporous adsorption resin (MAR), and column chromatography (CC) were employed to extract, enrich and separate SB, TV and TG from PSS, and the conditions were optimized. The results implied that SB (1.6937 g), TV (0.5884 g) and TG (3.8786 g) with the purity of 99.67 %, 99.32 % and 98.54 %, respectively, were obtained after the extraction, enrichment and separation. The total yields of the SB, TV and TG were 0.61 mg/g, 0.02 mg/g and 6.64 mg/g with the total extraction rates at 70.55 %, 69.77 % and 78.36 %, respectively. This is the first report on the large-scale extraction, enrichment and separation of oligostilbenes. The SOP in this paper could produce high purity SB, TV and TG, and provide a new idea for PSS as a new oligostilbene resource. The study expands the new development and research field of PSS and provides theoretical support for the green utilization of oil tree peony.     

Regioselective biomimetic oxidation of halogenated resveratrol for the synthesis of (±)-ε-viniferin and its analogues

FeCl₃·6H₂O-promoted biomimetic oxidations of 3,5-dihalogeno-resveratrol in different acetone systems produced several coupling intermediates bearing distinct dimeric skeletons with moderate yields. The subsequent deprotection reactions of brominated coupling products achieved the efficient synthesis of natural products (±)-ε-viniferin, (±)-ampelosin B, and (±)-gnetins F, as well as an unnatural oligostilbene. The coupling mechanisms for the formation of different dimeric structures were also proposed.     

Concise synthesis of several oligostilbenes from the enzyme-promoted oxidation of brominated resveratrol

The simple synthesis of (±)-parthenostilbenins A and B and (±)-quadrangularins A and B, as well as several unnatural resveratrol dimers, was successfully accomplished for the first time. Moreover, (±)-restrytisols B, (±)-leachianols F and G were efficiently prepared with higher yields compared with those in the literatures. The regioselective oxidative coupling reactions of 3,5-dibromo-resveratrol catalyzed by different enzymes in various solvent systems were used as key steps. The coupling mechanisms for the formation of distinct dimeric skeletons were also proposed.