ETEREOSPECIFIC SYNTHESIS OF α-D-FRUCTOFURANOSIDES——SYNTHESIS OF THE OLIGO-FRUCTAN DIASTEREOISOMERS

α-fructofuranosides were stereospecifically synthesized from 2-O-Ac-1,3,4,6-O-tetra-benzoylfructose by employing TMSOTf as a catalyst. Meanwhile,one diastereoisomer derivative of sucrose and two of fructan oligomers were synthesized.The structure of all products were confirmed by ^(13)C-NMR and ~1H-NMR spectra.

Synthesis of the (3R, 9S, 10S)-Diastereoisomer of Panaxytriol,a Potent Antitumor Polyacetylene from Panax ginseng

(3R, 9S, 10S)-Heptadec-1-ene-4,6-diyne-3, 9, 10-triol 2, a diastereoisomer of panaxytriol 1 was synthesized using L-(+)-diethyl tartrate 5 as a chiral template, through the Cadiot-Chodkiczwicz coupling of the terminal acetylene 3 with bromoacetylene 4.

Attempt to Resolute Chiral Clusters by Optically Active Hydrazide

A new kind of hydrazone (I) diastereoisomers was prepared with enantiomeric hydazide (II) and chiral cluster (III), which was characterized by HMBC. Unfortunately, the mixture could not be separated into pure diastereoisomer. This could be a direction to separate the racemic chiral clusters.

The Development of S-Equol Diastereoisomer Specific ELISA

Equol is a metabolite of soybean isoflavone, daidzein, and many health benefits are expected. Endogenous equol in urine is S-equol and mostly exists as glucuronate or sulfate conjugate. In this study we preliminary established the simple enzyme-linked immunosorbent assay (ELISA) without deconjugation, then developed the S-equol specific ELISA involves deconjugation showing high stereospecificity to S-equol without using stereospecific antibody. For the simple ELISA, we used a polyclonal antibody that targets the regions not influenced by inhibition by conjugation of glucuronate and sulfate and achieved the correlation coefficient;r = 0.975, but the value was 30 % lower than high performance liquid chromatography (HPLC). Developing upon this we invented the specific ELISA established from S-equol homogeneous combination for the standard and enzyme-labeled antigen to enhance stereospecificity. The correlation with HPLC was favorable: r = 0.986, y = 0.996x – 6. Compared to the previous method using (R,S)-equol combination, cross-reactivity with R-equol was reduced from 65 to 13 %, and that with daidzein from 0.31% to 0.08%, markedly increased in the specificity. This study is expected to be applied for both simple clinical researches, and stereospecific immunoassays in which specific antibody preparation is difficult.

Chiral resolution of furofuran lignans and their derivatives from the stems of Dendrobium'Sonia'

Five new furofuran lignans and their derivatives,(-)-glaberide I 4-O-β-D-glucopyranoside(1a),(+)-glaberide I 4-O-β-D-glucopyranoside(1b),(+)-glaberide I 7'-ethoxy-4-O-β-D-glucopyranoside(2a),(-)-glaberide I 7'-ethoxy-4-O-β-D-glucopyranoside(2b),and(-)-isoeucommin A(3b),along with fifteen known analogs were isolated from the stems of Dendrobium'Sonia'.These compounds were classified into ten pairs of enantiomers or diastereoisomers via chiral resolution,and their structures were determined based on extensive spectroscopic data.Their absolute configurations were determined by hydrolysis,comparison of experimental and calculated electronic circular dichroism(ECD)data,and single-crystal X-ray diffraction analysis.The isolates were evaluated for their ability to inhibit nitric oxide(NO)production in RAW264.7 cells.Among them,syringaresinol(5)exhibited prominent inhibition activity,with an IC50 value of 28.4±3.0μmol·L~(-1),and there was a slight difference between 5a,5b and the racemic mixture 5.

Temporal–spatial distribution and diastereoisomer pattern of hexabromocyclododecane in the vicinity of a chemical plant

Hexabromocyclododecane(HBCD) is an effective brominated flame-retardant additive, which is mainly produced in the coastal area of China. This study collected soil samples from a HBCD production plant and its surrounding area in Weifang, Shandong Province, China, and analyzed the temporal–spatial distribution of HBCD and its diastereoisomers in soil. The analysis results showed that the concentration of HBCD in soil near the plant was much higher than normal values, with an annual average concentration reaching 5405 ng/g. Soils 1,2 and 4 km away from the plant were also analyzed, showing that the concentration of HBCD in soil decreased accordingly with the distance from the pollution sources. In order to investigate the effect of the season on HBCD content, the soil samples were collected in all four seasons of the year 2017–2018. According to variations in the wind direction, the concentration of HBCD in soil was also changed. The distribution trend showed that the concentration of HBCD in soil in the downwind direction of the prevailing wind was higher than that in the upwind direction. In addition, this work analyzed the distribution of HBCD in vertical soil sections. It was found that the concentration of HBCD decreased with depth in the soil vertical profile. Finally, the various diastereoisomer patterns in the soil compartments were examined, finding that α-HBCD and γ-HBCD were the predominant diastereoisomers in the soil of the study area.

Lithocarpinols A and B,a pair of diastereomeric antineoplastic tenellone derivatives from the deep-sea derived fungus Phomopsis lithocarpus FS508

Lithocarpinols A(1) and B(2), a pair of tenellone diastereoisomers with novel fused skeleton were isolated from the deep-sea derived fungus Phomopsis lithocarpus FS508. Their structures were elucidated by comprehensive spectroscopic analyses, X-ray diffraction and quantum molecular calculation. Their plausible biogenetic pathway featured an intriguing carbonyl-ene cyclization. Lithocarpinol A exhibited moderate inhibitory effect against HepG-2 and A549 tumor cell lines with IC_(50) values of 9.4 μmol/L and10.9 μmol/L,respectively.

Development and validation of an HPLC-UV method for the separation of entecavir optical isomers

A simple and effective high-performance liquid chromatography with ultraviolet detection（HPLC-UV） method was established to determine entecavir optical isomers. With 3 chiral carbon atoms, entecavir had 7 optical isomers, including 6 diastereoisomers and 1 enantiomer. The separations were performed on a Symmetrix ODS-AQ C_（18） column（4.6 mm×250 mm, 5 μm） and a Daicel CHIRALPAK AD column（4.6 mm×250 mm, 10 μm）, respectively. The detection wavelength was set at 254 nm. The limit of detection（LOD） and the limit of quantification（LOQ） of diastereoisomers（diastereoisomer-1, diastereoisomer-2, diastereoisomer-3） were 0.0371, 0.0376, 0.0377, and 0.124, 0.125, 0.126 μg/mL, respectively. The LOD and LOQ of enantiomer were 0.14 and 0.46 μg/mL, respectively. The precision was within 0.36%, 0.44%, 1.04%, and 0.67% for diastereoisomer-1, diastereoisomer-2, diastereoisomer-3, and enantiomer, respectively. The recoveries of enantiomers ranged from 98.4% to 100.5%. The method could be applied to control the quality of entecavir.

The role of central ion in chiral recognition by taking phenylalanine as an example

Chiral recognition of phenylalanine(Phe) was achieved in the gas phase by electrospray ionization Q-TOF tandem mass spectrometry.In this method,two central ions,i.e.proton and divalent copper,were used and chiral crown ether,(+)-2,3,11,12-tetracarboxylic acid-18-crown-6(18-C-6-TCA),was used as a chiral host.Dimeric complexes were readily formed by electrospray ionization of a methanol/water(50/50,V/V) solution containing central ions,Phe and 18-C-6-TCA.The dimeric complex included proton-bound(18-C-6-TCA)(Phe)H+ and copper-bound deprotonated [Cu2+(18-C-6-TCA)(Phe)-H]+ ions were mass selected and then collided with Ar in the CID experiments.The chiral recognition capability of these complexes was evaluated using the relative abundance of daughter ion to parent ion.A higher degree of chiral recognition ability was observed with Cu2+ compared to that of H+.Different central ions exhibited distinctive dissociation pathways and unique chiral recognition characteristics.The chiral recognition mechanism was also discussed in detail with the help of the structure of copper-bound complex predicted by theoretical calculation.