Chemical approaches for the stereocontrolled synthesis of 1,2-cis-β-D-rhamnosides / 中国天然药物

In carbohydrate chemistry, the stereoselective synthesis of 1,2-cis-glycosides remains a formidable challenge. This complexity is comparable to the synthesis of 1,2-cis-β-D-mannosides, primarily due to the adverse anomeric and Δ-2 effects. Over the past decades, to attain β-stereoselectivity in D-rhamnosylation, researchers have devised numerous direct and indirect methodologies, including the hydrogen-bond-mediated aglycone delivery (HAD) method, the synthesis of β-D-mannoside paired with C6 deoxygenation, and the combined approach of 1,2-trans-glycosylation and C2 epimerization. This review elaborates on the advancements in β-D-rhamnosylation and its implications for the total synthesis of tiacumicin B and other physiologically relevant glycans.

Stereoselectivity of the Excretion of R-/S-HPABA in Rats / 中国药学杂志

OBJECTIVE: To develop an UHPLC-MS/MS method for the determination of R-/S-2-(2-hydroxypropanamido) benzoic acid (R-/S-HPABA) in rat urine, feces and bile and apply the method to study the excretion of R-/S-HPABA in rats. METHODS: After liquid-liquid extraction by ethyl acetate,the separation was achieved on a Thermo Syncronis C18 column (2.1 mm×50 mm, 1.7 μm) using mobile phase consisting of solvent A (methanol) and solvent B (0.1% formic acid) at a flow rate of 0.4 mL•min-1. The concentration of R-/S-HPABA after single dose oral administration of 50 mg•kg-1 R-/S-HPABA to rats was detected by UHPLC-MS/MS method. RESULTS: The calibration curve was linear over the range of 0.002-5 μg•mL-1 and the lower limit of quantification (LLOQ) was 0.002 μg•mL-1. The intra-and inter-day RSDs were less than 13.0% and the accuracy (relative error) of R-/S-HPABA was within -7.5%-4.2%. The average recoveries were (87.3±3.4)%-(104.4±7.0)%. After intragastric administration of R-HPABA and S-HPABA at a dose of 50 mg•kg-1, the cumulative amounts of R-HPABA and S-HPABA excreted in the urine (0-48 h) were (536.1±29.7) and (771.7±38.6) μg, the urinary excretion amounted to 4.9% and 7.0% of the dosage, respectively; the cumulative amounts of R-HPABA and S-HPABA excreted in feces (0-48 h) were (3 963.0±345.2) and (4 771.8±355.0) μg, the fecal excretion amounted to 36.0% and 43.4% of the dosage, respectively; the cumulative amounts of R-HPABA and S-HPABA excreted in bile (0-12 h) were (150.6±30.3) and (747.7±89.2) μg, the biliary excretion amounted to 1.4% and 6.8% of the dosage, respectively; the summation of urinary, fecal and biliary excretion amounted to 42.3% and 57.2% of the dosage in rats for R-HPABA and S-HPABA, respectively. The cumulative amounts of S-HPABA excreted in the urine, feces and bile were higher than those of R-HPABA. CONCLUSION: This UHPLC-MS/MS method is suitable for the study of the excretion of R-/S-HPABA in rats. The excretion of the two enantiomers in rats shows significant stereoselectivity difference.

Recent advances in directed evolution / 生物工程学报

Screening is the bottleneck of directed evolution. In order to address this problem, a series of novel semi-rational designed strategies have been developed based on combinatorial active-site saturation test and iterative saturation mutagenesis, including single code saturation mutagenesis, double code saturation mutagenesis and triple code saturation mutagenesis. By creation of "small and smart" high qualified mutant libraries and combinatorial mutagenesis of specific sites, these new strategies have been successfully applied in multiparameter optimization, e.g. stereo/regioselectivity and activity. This review summarized recent advances in directed evolution and its applications in biocatalysis field.

System for chiral antidepressant evaluation and related application / 中国药理学通报

Currently, most commercially available antidepres-sants have one or more chiral centers,and development of chiral antidepressants are of great interest for researchers. Thalidomide induced tragedy promotes drug evaluation centers from various countries to reevaluate their current guidelines and recommend single enantiomer application when developing a chiral antide-pressant. Unfortunately,as far to our knowledge,traditional en-antiomers comparison and active enantiomer selection are real-ized by simple comparison using in vitro targets data. Our team established an integrated system for chiral antidepressant evalua-tion and active enantiomer screening based on four modules,in-cluding pharmacodynamic comparison,pharmacokinetic compar-ison, toxicological comparison, and comprehensive factors. Here,we review this integrated system and make a detailed a-nalysis taking ammoxetine as a realistic example.

Research progress in the synthesis of tumor-associated carbohydrate antigens (TACAs) GM3 and de rivatives / 药学实践杂志

Glycosylation is the key step of the synthesis of GM3 ,its reaction conditions are very harsh ,the stereoselec‐tivities are usually poor ,and the configuration of anomeric carbon is difficult to control .Whetherαglycosidic bond can be con‐structed efficiently in sialylation reactions is an important criteria used to evaluate the reaction quality .Studies of GM3 and de‐rivatives methods generally relates to following areas :the choice of the donor compounds and receptor compounds ,the control of stereoselectivity ,and the development of some new glycosidic reaction catalyst .In recent years ,important progress has been made in this research area .Now ,we predominately make a summary and review on the progress of methods for the synthesis of GM3 and derivatives .

Stereoselective pharmacokinetics of itraconazole enantiomers in rats / 中国药科大学学报

@#To investigate the stereoselective pharmacokinetics of itraconazole enantiomers in rats, four cis-ITR stereoisomers at the dose of 15 mg/kg were administered orally to rats. Blood was collected and single stereoisomer of ITZ and hydroxy-itraconazole(OH-ITZ)were determinated simultaneously by LC-MS/MS. Samples were extracted by protein precipitation with acetonitrile. Durashell HILIC column(100 mm×2. 1 mm, 5. 0 m)was used as the analytical column, while a mixture of solvent A(0. 02% acetic acid and 5 mmol/L ammonium acetate in water)and B(50% acetonitrile and 50% methyl alcohol)was used as the mobile phase. A 5. 5 min binary gradient elution(delivered at 0. 5 mL/min)was performed for the separation. LC-MS/MS was performed in positive ion mode with multiple reactions monitoring(MRM). The pharmacokinetic parameters of itraconazole enantiomers after the administration were estimated as follows: the plasma levels and AUC0-∞ of OH-(2S, 4R, 2R)-ITZ and OH-(2S, 4R, 2S)-ITZ were higher than those of OH-(2R, 4S, 2R)-ITZ and OH-(2R, 4S, 2S)-ITZ(P< 0. 001). At the same time, female rats exhibited greater cmax, t1/2, AUC0-∞ than male rats, and the absorption of male rats was more rapid than those of females. The findings indicate significant stereoselective differences in the pharmacokinetic parameters of itraconazole enantiomers and gender difference in rats.

Analysis of chiral non-steroidal anti-inflammatory drugs flurbiprofen, ketoprofen and etodolac binding with HSA / 药物分析学报

The protein binding of non-steroidal anti-inflammatory drugs flurbiprofen,ketoprofen and etodolac with human serum albumin (HSA) was investigated using indirect chiral high performance liquid chromatography (HPLC) and ultrafiltration techniques.S-(-)-2-(1-naphthyl)-ethylamine (S-NEA) was utilized as chiral derivatization reagent and pre-column derivatization RP-HPLC method was established for the separation and assay of the three pairs of enantiomer.The method had good linear relationship over the investigated concentration range without interference.The average extraction efficiency was higher than 85％ in different systems,and the intra-day and inter-day precisions were less than 15％.In serum albumin,the protein binding of etodolac enantiomers showed significant stereoselectivity that the affinity of S-enantiomer was stronger than R-enantiomer,and the stereoselectivity ratio reached 6.06; Flurbiprofen had only weak stereoselectivity in HSA,and ketoprofen had no stereoselectivity at all.Scatchard curves showed that all the three chiral drugs had two types of binding sites in HSA.

Analysis of chiral non-steroidal anti-inflammatory drugs flurbiprofen, ketoprofen and etodolac binding with HSA / 药物分析学报

The protein binding of non-steroidal anti-inflammatory drugs flurbiprofen, ketoprofen and etodolac with human serum albumin （HSA） was investigated using indirect chiral high performance liquid chromatography （HPLC） and ultrafiltration techniques. S-（-）-1-（1-naphthyl）- ethylamine （S-NEA） was utilized as chiral derivatization reagent and pre-column derivatization RP-HPLC method was established for the separation and assay of the three pairs of enantiomer. The method had good linear relationship over the investigated concentration range without interference. The average extraction efficiency was higher than 85% in different systems, and the intra-day and inter-day precisions were less than 15%. In serum albumin, the protein binding of etodolac enantiomers showed significant stereoselectivity that the affinity of S-enantiomer was stronger than R-enantiomer, and the stereoselectivity ratio reached 6.06; Flurbiprofen had only weak stereoselectivity in HSA, and ketoprofen had no stereoselectivity at all. Scatchard curves showed that all the three chiral drugs had two types of binding sites in HSA.

Two step process for diketo-reduction catalyzed by diketoreductase / 中国药科大学学报

Diketoreductase can catalyze a double reduction of β,δ-diketo ester to corresponding dihydroxv product with enantiomeric excess(ee)and diastereomeric excess(de)both greater than 99.5%.In order to explore the catalytic mechanism of this unique enzyme,the present study investigated the diketone reduction process and reaction characteristics by diketoreductase.We found that two mono-hydroxy intermediates were produced during the diketone reduction and its reverse reaction.The two intermediates were further separated by C18 column chromatography and structurally confirmed by chiral HPLC with authentic standards.Two mono-hydroxy intermediates could be served as the substrates for the reduction by diketoreductase with different reaction velocities.The formation and disappearance of intermediates were largely affected by temperature and substrate concentration.In addition,steady state kinetics with the two intermediates showed different reaction rates in their disappearance.Collectively,the results indicate that the diketone reduction undergoes a two-step process with the formation of both intermediates,but the disappearance rates for the two intermediates are slightly different.

Stereoselective bile excretion of ibuprofen glucuronide and the transport mechanism in the biliary efflux / 中国临床药理学与治疗学

AIM: To illustrate the effects of drug transporters on the bile efflux of ibuprofen glucuronide(IBG), the difference of bile excretion and plasma concentration of ibuprofen(IB) and its glucuronides was studied in EHBR and normal SD rat(SDR). METHODS: After 20 mg/kg of IB enantiomers administrated intravenously, the bile and blood were collected from the rats and the concentration of IB and their glucuronide were measured by HPLC methods. RESULTS: The bile excretion of IBG was obviously (but no totally) suppressed in EHBR (1.7%±1.0%, 0.6%±0.9% of the dose respectively for S-IBG and R-IBG) compared with that in SDR (18.4%±4.0% and 3.0%±2.4% of the dose respectively for S-IBG and R-IBG), for both kinds of rats, there are more S-IBG excreted than that of R-IBG. As the result of reduction of IBG excreted in bile, the concentration of IBG was higher in blood in EHBRs. CONCLUSION: The results suggest that Mrp2 is the most important transporter for IBG, and other transporter(s) may participate in the process.