Phase Structures of Microemulsions Determined by the Steady-State Fluorescence Method

Experimental The pyrene was purchased from Sigma Co., and the other chemicals were of A. R. grade. Water was deionized and distilled twice before use. The microemulsions of required compositions were prepared in the following way. The stock microemulsions were made without water at first, corresponding to the A point (10wt% octane, 63wt% n-butanol, 27wt% CTAB) in the phase diagram of Figure 1 and then a series of microemulsions were made along AW dilution line with adding water. Calcu…     

Application of Pac Ester in Thioester Method for the Synthesis of Cyclopentapeptides

Thioester method for the synthesis of cyclopeptides is improved by using Pac (Pac = phenacyl, CH2COC6Hs) ester as a protecting group of 3-mercaptopropionic acid. The Pac group is easy to be removed from C-terminal with zinc in acetic acid. The protected glycine thioester and peptide thioesters synthesized by the improved method, are easy to be purified, so the final linear peptides are pure enough for the following cyclization. Furthermore, this method is flexible for peptide chain elongation,either from C-termlnal or from N.terminal. So it is an efficient and practical method for synthesis of bioactive peptides. Two N-protected pentapeptide thioesters, Boc-Pro-Tyr-Leu-Ala-GIySCH2CH2COOPac and Boc-Ala-Tyr-Leu-Ala-Gly-SCH2CH2COOPac were synthesized by the improved thloester method.After deprotecting Pac ester with zinc in aqueous acetic acid and Boc group with trifluoroacetic acid in CH2C12, two free pentapeptide tldoesters were obtained. Ag^ -assisted cyclization in acetate buffered solution afforded two cyclic pentapeptides c(Pro-Tyr-Leu-Ala-Gly) and c(Ala-Tyr-Leu-Ala-Gly).Effects of different buffer pH, different Ag^ concentrations, etc. on the cyclization were studied.     

Thin-Layer Chromatography—Image Analysis Method for the Simultaneous Quantification of Andrographolide and Related Diterpenoids in Andrographis paniculata

JPC – Journal of Planar Chromatography – Modern TLC -     

LC–MS Method for the Quantification of Clonazepam in Rat Plasma

A sensitive and specific high-performance liquid chromatography–tandem mass spectrometry method has been developed and validated for the determination of clonazepam in rat plasma. Clonazepam and internal standard diazepam were extracted from plasma samples by a single-step protein precipitation. The chromatographic separation was performed on a Dikma ODS-C18 reversed-phase column at 40 °C. The mobile phase composed of a premix of solvent A (0.1% formic acid–4 mM ammonium acetate–water)–solvent B (acetonitrile) (13:87, v/v) at a flow-rate of 0.7 mL min^?1. Positive electrospray ionization was utilized as the ionization source. Clonazepam and the internal standard were determined using multiple reaction monitoring of precursor → product ion transitions at m/z 316.0 → 270.0 and m/z 285.1 → 193.2, respectively. The lower limit of quantification was 0.25 ng mL^?1 using 50 μL plasma samples and the linear calibration range was from 0.25 to 128 ng mL^?1. The within- and between-batch RSDs were lower than 15% and the relative recoveries of clonazepam ranged from 97.4 to 104.7%. The mean extraction recoveries of clonazepam and IS were 79.7 and 77.6%, respectively. The method has been successfully applied to the pharmacokinetic studies in rat after oral administration of clonazepam.     

Method for mild trimethylsilylation of the 14α-hydroxy group in ecdysteroids

In the reactions of poststerone derivatives and 20-hydroxyecdysone with (trifluoromethyl)trimethylsilane catalyzed by tetrabutylammonium fluoride, the 14-hydroxy group is readily subjected to trimethylsilylation.     

A Convenient Method for the Generation of Dihalocarbenes

Yamawaki reported that alumina coated with potassium fluoride(KF-Al_2O_3),could b(?)used as a strong base to promote the generation of dichlorocarben(?) from chloroform,usingcyclohexene as the trapping agent.However,the yield of 7,7-dichlorobicyclo-[4.1.0]hep-     

Development of an RPLC-based Method for Measurement of Indoprofen Stability and Validation of the Method

A method for quantitative measurement of the photochemical decomposition of the anti-inflammatory agent, indoprofen （INP） is descriped. An RPLC-based assay that could determine the extent of degradation of INP in a rapid, sensitive, and accurate manner was developed. The method was validated under photoirradiation. Quantitation was monitored with an Inertsil ODS-3V column using a mobile phase of acetonitril and 1% HOAc solution in deionized H2O. Statistics relevant to the system criteria, peak integrity and resolution among the parent drug and its degradation products were performed. From the intra- and inter-day tests, the coefficients of variation were found to range from 0.59% to 4.25% for the former and from 0.71% to 4.86% for the latter. The good selectivity and specificity of this RPLC-based procedure render it suitable for measurements of INP stability.     

Reductive Cleavage of the S-Si Bond in Phenylthio-trimethylsilane:A Novel Method for the Synthesis of Thiolesters

TheaPPlicationofsamariumdiiodideinorganicSyntilesishasreceivedmoreandmoreattenhoninthelastdecade.'-'Itisapowerfulone-electrontr~ferreducest.Recently,wehaveconsideredthattheS-Stbondmightbereductivelycleavedwithsamariumdiiodide.Thiolestersareusefulintermediatesinorgbocchemistry.'-'Manynewmethodshavebeendevelopedforthepreparationoftlilolestersinrecentyears,'-"forexample,tilereachonbetWeensodiumthiobenzoateandarenediazoniumtetaluoroborates,'beatmentofnitrosoamidesornitroamideswithinercaptansint…     

Novel Method for the Enantioselective Synthesis of β-Lactams

A novel method for the enantioselective synthesis of β-lactams is described in this study. 2,3-Dihydrobenzooxazin-4-one derived from salicylamide and L-menthone was used as the chiral auxiliary, which reacted with a-bromo-acyl bromides in the presence of pyridine to give carboximides 2. The stereo-controlled Reformatsky-type reactions of carboximides with imines yielded the corresponding trans β-lactams with high enantioselectivities（e.e. 75%-86%） and high chemical yields（63%-85%）, meanwhile, the chiral auxiliary dihydrobenzooxazin-4-one was released and recovered.     

Novel Method for the Enantioselective Synthesis of β-Lactams

A novel method for the enantioselective synthesis of β-lactams is described in this study.2,3-Dihydrobenzooxazin-4-one derived from salicylamide and L-menthone was used as the chiral auxiliary, which reacted with α-bromo-acyl bromides in the presence of pyridine to give carboximides 2. The stereo-controlled Reformatsky-type reactions of carboximides with imines yielded the corresponding trans β-lactams with high enantioselectivities(e.e. 75%-86%) and high chemical yields(63%-85%), meanwhile, the chiral auxiliary dihydrobenzooxazin-4-one was released and recovered.     

A New Method for the Synthesis of Ketone Diperoxide

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A Convenient Method for the Synthesis of Distamycin Analogue

A novel distamycin analogue was synthesized by chloroform reaction and DCC/HOBT coupling reaction without using amino protection and deprotection.     

Convenient Method for the 3‐Functionalization of Isoindazoles

The C‐3 position of isoindazoles is readily functionalized by metalation with lithium diisopropylamide followed by reaction with a variety of electrophiles.     

An Expedient Method for the Synthesis of Thiosemicarbazones under Microwave Irradiation in Solvent-free Medium

A simple,efficient and eco-friendly method for the synthesis of thiosemicarbazones from thiosemicarbazidesand aldehyde under microwave irradiation has been reported,and no solvent and catalyst were used.And the tech-nique of microwave irradiation coupled with solvent-free condition proved to be a quite valuable method in the or-ganic synthesis.     

LC–Tandem-MS Validation for the Quantitative Analysis of Levonorgestrel in Human Plasma

In this study, a rapid, sensitive and reproducible liquid chromatography–tandem mass spectrometry method for the determination of levonorgestrel in human plasma, was developed and validated. With a structural analogue norethindrone as the internal standard, levonorgestrel was extracted from plasma using ethyl acetate. The organic layer was evaporated to dryness and the residue was reconstituted in mobile phase. An aliquot of 20 μL was chromatographically analyzed on a Phenomenex Luna C₁₈ column with water and acetonitrile as the mobile phase. Selected reaction monitoring was specific for mass detection employing positive electrospray ionization. The calibration standards were linear over the concentration range 0.625–40 ng mL^?1. The intra- and inter-day precision over the entire concentration range were less than 8.16%. The method was found to be suitable for application to a pharmacokinetic study after oral administration of 1.5 mg levonorgestrel tablet to 20 healthy female volunteers.     

Facile and Green Method for the Synthesis of β-Aminoketone Derivatives in Aqueous Media

Three-component reaction of aromatic aldehyde, 2-naphthalenamine, and 1,2-diphenylethanone in aqueous media catalyzed by triethylbenzylammonium chloride (TEBAC) at 90 °C gave 3-aryl-3-(naphthalen-2-ylamino)-1,2-diphenylpropan-1-one derivatives. The enol form of 1,2-diphenylethanone was tentatively proposed to participate in the formation of the products. Compared with previous methods, this three-component reaction has the advantages of green solvent, good yields, and operational simplicity.     

Facile Method for the Large-Scale Synthesis of 6,7,4′-Trihydroxyisoflavanone

6,7,4′-Trihydroxyisoflavanone, the main source of which is extracted from soybeans, has been found to have diverse significant bioactivities. A large-scale, cost-effective, and facile chemical synthesis of 6,7,4′-trihydroxyisoflavanone is presented herein. Its synthesis is characterized by three steps with an overall yield of 71% and a purity or more than 99.0%. This reaction can be scaled up to multikilogram quantities, providing a solid basis for its further bioactivity studies and drug development. With this same method, 6,7,3′,4′-tetrahydroxyisoflavanone, an analog of 6,7,4′-trihydroxyisoflavanone, also can be largely prepared, indicating this modified synthetic method is potentially available for large-scale synthesis of a broad range of multihydroxyl isoflavanones.     

A Convenient Method for the Asymmetric Synthesis of KAD-1229

A new method for preparation of the potent hypoglycemic KAD-1229 was developed.The key step of this method is diasteroselective alkylation in high optical purity and good yield by using easily available Oppolzer‘s camphor sultam as chiral auxiliary.     

An Improved Method for the Syntheses of β-Substituted Cyclohexenones

An improved method for the preparation of β-substituted cyclohexenones is reported. Conditions were defined to effectuate the key desulfonylation-deketalization step in a mild manner. Several cyclohexenones bearing acid and/or base sensitive β-substituents were prepared by the modified method in moderate to good yields.     

Sonochemical Method for the Preparation of Hollow SnO2 Microspheres

A simple sonochemical route has been successfully developed to synthesize SnO_2 hollow microspheres.Theobtained sample is characterized by XRD,TEM,XPS and UV-visible spectrophotometer.The TEM image of thesample at high magnification shows that the shell of the hollow sphere is composed of 3-5 nm SnO_2 nanoparticles.A possible formation mechanism of the hollow spheres is briefly discussed.