A Simple Method for the Preparation of ZnO Prickly Spheres

The synthesis of ZnO prickly spheres using precipitation followed by heating treatment was investigated. Zn(OH)2 precursor was prepared by precipitation process using Zn(CH3COO)2-2H2O in mixed 1-propanol-water solvent. Sodium dodecyl sulfate (SDS) as the anionic surfactant was added to control the morphology. The size and structure of ZnO prickly spheres were studied using XRD, TEM and SEM. The results showed that the morphologies and size of the spheres strongly depended on the volume ratio of 1-propanol /water and molar ratio of SDS/Zn2+. ZnO prickly spheres composed of nanorods could be obtained, when the volume ratio of 1-propanol/water = 2:3 and the molar ratio of Zn2/SDS= 450:1.     

Selectively reductive cleavage of the protected taxol side chain with sodium borohydride

During the course of our studies on the taxol chemistry,we have ever tried thereductive cleavage of the acotyl group at 20-C in compound 1a~(1,2) with the hydroxylgroup assistance at 4-C by sodium borohydride. However, the major product 2a~2(27%)still had the acetyl group at 20-C and the signal for the 10-C proton at 6.61 ppm(s)was shifted to 6.31 ppm(d, J=3.79 Hz). A new doublet signal at 3.62 ppm(d, J=3.80     

A Simple Approach to Control the Growth of Non-spherical Gold Nanoparticles

A simple method to prepare the non-spherical gold particles was developed. The result solution included trigonal, truncated trigonal, hexagonal layers, and a pseudo-pentagonal shaped gold nanocrystals. The key factor is to control the relative rates of nucleation and cluster growth in this method. These attributes make seeding growth method as a useful tool in the fabrication of colloidal metal materials. A longitudinal plasmon resonance of 866 nm was observed, which is in the near-IR spectral regions (600-1000 nm). The excellent optical properties as near-IR labels are used to develop highly sensitive analvsis method.     

A Facile Method for Monoesterification of α, ω-Dicarboxylic Acids: Application to the Synthesis of Traumatic Acid,A Prostaglandin Synthon

During the past decade, methyl 7-(5-oxocyclopentenyl)heptanoate (6) has been frequently used as a key intermediate in prostaglandin synthesis.¹ Although keto ester 6 can be readily obtained by treatment of traumatic acid (5) with polyphosphoric acid followed by esterification with methanolic hydrochloric acid,² this approach is not attractive for large-scale synthesis due to the expense of the latter natural product (5). Recently Salomon and Reuter have reported¹ an alternate route to synthon 6 based on a starting material derived from aleuritic acid, a major component of shellac.     

A New Method for the Synthesis of C/D Ring Synthon of Vitamin D

Inrecentyears,vitaminDresearchareahasbeenstimulatedbythediscoveriesthatIQ,25-dihydroxyvitaminD,,theactivemetaboliteofvitaminD,,inadditiontotheclassicalrolesofregulatingcalciumandphosphorusmetabolisms',hasamuchbroaderspectrumofactivitiesthanoriginallythought,suchaspromotingcelldifferelltiationandinhibitingcellproliferation"'.Thebiologicalsignificanceandmedicalneedshaveledeffortstowardthesearchforanaloguesofpotentcelldifferelltiationandantiproliferationactivitywithouttoxichypercalcemiaassociate…     

A Simple and Efficient Procedure for the Preparation of O-aryl-O-ethyl-S-allyl Thiolophosphates

HubeiNaturalScienceFoundationforfinancialsupportChap-cyethy-S-allylthiOlwioSPhates(2a-j)havePOtenhalbiologicalachvihes.Inl983,Y.TamaruandZYoshidarePOrtedPallatuxn(o)catalyZedthiono-ffooloallylicrearr~mentOfcrallylphoSPhoro-andphoSPhonotheonaes,andaiSOreinvestigaedthennalrearrangementOfa-andy-methallyldiethyphOSPhorothionaesinrelallontotheregioselectivityObserVedinthePalladium(O)catalySisl'].InourPreviousStUdy,Hg(II)catalghcandthermalffoono-ffoolorearrangmentOfcrPrOPargylcreqlp…     

Simple Approach to the Highly Stereoselective Synthesis of trans-1,2-Cyclopropane Derivatives

In the presence of KF·2H2O, furoylmethyltriphenylarsonium bromide （1a） or thienoylmethyltriphenylarsonium bromide （1b） reacted with 2-[（un）substituted benzylidene]malononitrile （2） in chloroform at room temperature to give trans-3,3-dicyano-1-furoyl-2-[（un）substituted phenyl]cyclopropane （3a） or trans-3,3-dicyano-1-thienoyl-2- [（un）substituted phenyl]cyclopropane （3b） respectively in good yield with high stereoselectivity. The structures of product 3 were confirmed by IR, MS, 1^H NMR, 1^H-1^H COSY and microanalysis. The relative configuration of product 3 was determined by 1^H-1^H NOESY technique. The mechanism for the formation of product 3 was also proposed.     

Dramatic Solvent Effect in the Reduction of 2,3—Allenoic Acid Esters.A Simple Synthesis of 2,3—Allenols from 2,3—Allenoates

2，3－Allenols were prepared conveniently from the reduction reaction of 2,3-allenoates with DIBAL-H(Diisobutylaluminum hydride) in toluene.A dramatic solvent effect was observed for this reaction.     

Modification of Norditerpenoid Alkaloids:Ⅱ.A Simple andConvenient Preparation of the Imine Derivatives of Norditerpenoid Alkaloids

Interestthenloditlcationofthenorditerpenoidalkaloidsledustopreparationoftheiminederivatives.Preparationmethodsoftheimmeshavebeensummed.includingoxidationa"ithCrO,/pyridine=,rearrangementofchloroamines3andheatingsomeoxazolidine-containingorhavingO.N-mixednorditerpenoidalkaloidssuchasisoatisine1'andajaconine2',withAc=O-pyridine.Inaddition.oxidationof3'withPh(OAc).isalsousedtarthispurpose.In1995,Fuente,elalpreparedanimine5(21%)startingfromperegrine4byoxidationofKMnO./acetone-H,O(2;1)'.Inthe…     

New Approach to Analysis of the Nonlinearity of the Brønsted Relationship: II. An Empirical Procedure Combining the σρ Correlation Method with the Concept of Hard and Soft Acids and Bases,as Applied to Pseudo CH Acids

A comparative systematic analysis of the features of Brönsted behavior of pseudo CH acids(according to Eigen's classification) is made. The analysis is based on combined use of experimental data onpK _a, Ggas, logk _D of CH acids (Ggas is the free energy of acid ionization in the gas phase, logk _D isthe logarithm of the rate constant of hydrogen exchange in a protic solvent). The modified nucleophilicKabachnik constants ^- are applicable to correlations for all the three kinds of acidity of pseudo CH acids. The electrostatic solvation makes an insignificant contribution to variation of pK _a and weakening of the substituent effect in going from the gas phase to dimethyl sulfoxide, and also to differentiation of the kinetic acidity. The coefficient in the Brönsted equation and the ratio between the rate constants in the correlations, which characterize the degree of proton transfer in the reaction transition state, have much in common from the physical viewpoint. The results of correlation analysis, demonstrating intramolecular uniformity of the interactions, are fully consistent with the conclusion made in the previous part of this work about the solvation uniformity of the interactions, resulting in the absence of thermodynamic deviations from the Brönsted relationship.     

A Method for Preparing Phosphinic Acids from Hypophosphites: III. Synthesis of α-Hydroxy Phosphinic Acids

A one-pot method is proposed for preparing unsymmetrical -hydroxy phosphinic acids from ammonium hypophosphite. Bis(trimethylsilyl) phosphonites formed in situ on addition of bis(trimethylsilyl) hypophosphite to activated unsaturated compounds are brought without isolation into the Abramov reaction with an aldehyde or ketone. A series of new -hydroxy phosphinic acids are obtained.     

A Concise Approach to the Synthesis of L-and D-Deoxyribose

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Semisynthetic β-Rhodomycins: A New Approach to the Synthesis of 4-O-Methyl-β-Rhodomycins

ABSTRACT

Syntheses of 4-O-methyl-β-rhodomycins are described. Glycosylation (trimethylsilyl triflate, dichloromethane-acetone 10:1, -30 °C) of 4-O-methyl-10-O-p-nitrobenzoyl-β-rhodomycinone, obtained from β-rhodomycinone (βRMN) in a 6-step synthesis, with 1-O-tert-butyl(dimethyl)silylated derivatives of 4-O-acetyl- or 4-O-p-nitrobenzoyl-2,3,6-tri-deoxy-3-trifluoroacetylamino-β-L-arabino- and lyxo-hexopyranoses or 2,6-di-O-acetyl-2,6-dideoxy-β-L-lyxo-hexopyranose afforded 7-O-α-L-glycosyl-β-rhodomycinones. Removal of the O- and N-acyl groups with 0.1M and 1M NaOH gave the 7-O-(3-amino-2,3,6-trideoxy-α-L-arabino- and lyxo-hexopyranosyl)-4-O-methyl-β-rhodomycinones and 7-O-(2,6-dideoxy-α-L-lyxo-hexopyranosyl)-4-O-methyl-β-rhodomycinone.     

Exceptionally Simple Homologation of Protected α‐ to β‐Amino Acids in the Presence of Silica Gel

The Wolff rearrangement of α‐amino acid–derived diazoketones is simply achieved by gentle warming in a ethyl acetate/silica gel slurry containing catalytic amounts of silver trifluoroacetate. Without workup (not counting filtration and evaporation) the protected β‐amino acids are obtained in high yields (92–97%) without significant impurities. This variation avoids the laborious workup after a conventional silver‐catalyzed Wolff rearrangement. This method can be similarly applied to the synthesis of β‐amino acid methyl esters when methanol is used as solvent. No reaction occurs without silica gel.     

Intramolecular Oxidative Coupling of the Bis Enolate Derived from Dimethyl β,β-Dimethylglutarate: A Facile Stereoselective Route to a Versatile Synthon for Preparation of Insecticidal Pyrethroids

Treatment of the bis enolate derived from dimethyl β,β-dimethylglutarate with silver chloride afforded dimethyl cis-3,3-dimethyl-1,2-cyclopropanedicarboxylate, a versatile synthon for the preparation of the acid component of cis-pyrethroids. A similar experiment utilizing iodine as the oxidant led to the isolation of the corresponding trans diester with good stereo-selectivity.     

A General Approach for the Enantioselective Synthesis of anti-β-Hydroxy-α-Amino Acids: Preparation of an Oxazolidine-Functionalized Chiral Glycine Equivalent

The preparation of 2,4-disubstituted oxazolidine-functionalized glycine ester 3a derived from phenylglycinol is described.

     

Reaction of Polyfluorinated β-Diimines with Ketones. A Novel Method for the Synthesis of Fluorinated Pyridines

Reaction of polyfluorinated -diimines with ketones gave polyfluorinated pyridines     

Efficient and Rapid Method for the Oxidation of Electron‐Rich Aromatic Aldehydes to Carboxylic Acids Using Improved Basic Hydrogen Peroxide

An efficient and rapid method for oxidation of electron‐rich aromatic aldehydes to their corresponding carboxylic acids in excellent yields was developed. It is based on the oxidation of methoxy‐substituted benzaldehydes in methanol with an improved aqueous basic hydrogen peroxide system. Benzaldehydes with electron‐withdrawing substituents are oxidized to the corresponding carboxylic acid in excellent yields under mild reaction conditions.