An efficient procedure for the preparation of 4-substituted 5-aminoimidazoles

The preparation of O-methylimidates from alpha-aminonitriles and their subsequent co-cyclization with primary amines to afford 4-substituted 5-aminoimidazoles was studied. It was found that the mildly acidic pyridinium p-toluenesulfonate efficiently catalyzed each stage of the reaction sequence: (a) the formation of the O-methylimidates, (b) their co-cyclization with a variety of primary amines, and (c) certain derivatizations of the resultant heterocycles. The developed reaction conditions tolerate a wide variety of alpha-aminonitriles and primary amine co-reactants. Thus, it is possible to easily prepare a diverse array of substituted heterocyclic compounds in good yield. The requisite alpha-aminonitriles were synthesized either from amino acids or by phase-transfer alkylation of a glycine anion equivalent. The unstable free 5-aminoimidazoles were normally protected in situ to provide derivatives (methyl imidates or N,N-dimethylamidines) that were amenable to characterization.     

An efficient of Grignard-type procedure for the preparation of gem-diallylated compound

An efficient and a new procedure for the conversion of various carboxylic acid derivatives into the corresponding gem-diallylated compound under mild reaction condition has been developed. The triallylaluminum mediated Grignard-type addition of carboxylic acid derivative was utilized as a key operation to affect the transformation. The procedure is operationally simple, giving good to excellent product yields for a broad range of substrates. The chemoselectivity and regioselectivity of triallylaluminum were also demonstrated.     

An improved procedure for the preparation of 2-isoxazolines

Aldoximes were converted in high yields by N-Chlorosuccinimide into hydroxamic acid chlorides, and corresponding nitrile oxides generated by addition of triethylamine at 40°–50° underwent 1,3-dipolar polar addition to alkenes, giving 2-isoxazolines. The whole procedure could be performed as a one-pot reaction. Oximes with other functions, sensitive to free chlorine could be converted selectively into hydroxamic acid chlorides by this procedure. Isopropylidene glyceraldoxime was added to acrolein diethylacetal thus affording an entrance to carbohydrate synthesis but the stereospecificity of the reaction is low. 2:3, 5:6-Di-O-isopropylidene-D-mannose oxime was converted to the N-hydroximinolactone by treatment with NCS and base.     

A highly efficient procedure for 3-sulfenylation of indole-2-carboxylates

A highly efficient one-pot procedure for 3-sulfenylation of 2-carboxyindoles is described. Treatment of thiols with N-chlorosuccinimide at -78 degrees C in CH(2)Cl(2) affords sulfenyl chlorides in situ that readily react with 2-carboxyindoles to give 3-thioindoles in high yields. This new method is milder, produces less waste, and is compatible with a wide range of thiol and indole functionality. [reaction: see text]     

New and efficient procedure for the preparation of unsymmetrical silaketals

[reaction: see text] A new and efficient procedure for the preparation of unsymmetrical silaketals via a three-step protocol without isolation of the intermediates is presented. The unsymmetrical silyl ethers and silanes can also be readily obtained via this sequence of reactions.     

An improved and efficient procedure for the preparation of chiral sulfinates from sulfonyl chloride using triphenylphosphine

An improved procedure of the Sharpless method for the preparation of chiral sulfinates by triphenylphosphine is described. A mixture of sulfonyl chlorides and diacetone-d-glucose or l-menthol in the presence of triethylamine was treated with triphenylphosphine in CH₂Cl₂ at 0°C to give the sulfinates in good yields.     

An efficient and improved procedure for preparation of triflyl azide and application in catalytic diazotransfer reaction

An efficient and improved procedure for preparation of triflyl azide and application in catalytic diazotransfer reaction are described. The amount of highly toxic reagents NaN₃ and Tf₂O, is significantly reduced comparing with the previous protocol.     

An improved synthesis of anticancer benzothiopyranoindazoles. An efficient large-scale β-aminoethylation procedure

Improved processes for the synthesis of bulk quantities of the benzothiopyranoindazole clinical agent CI-958 and A-ring congeners is reported. The process chosen for scale-up operations achieves β-aminoethylation of an anilino precursor via a three-step sequence (acylation, reduction, deprotection) starting from N-(trityl)glycine. Detailed analytical data are reported for the target compounds and most intermediates, and detailed spectroscopy is given for CI-958.     

An improved procedure for the preparation of 9-β-D-Arabitiofuranosyl-2-ñuoroadenine

An improved procedure for the preparation of 9-β-D -arabinofuranosyl-2-fluoroadenitie (11) utilizing the readily available 2,4,5,6-tetraaminopyrimidine (1) is described; the overall yield based on the arabinosugar was quadrupled.     

An efficient procedure for the synthesis of 2-N-Boc-amino-3,5-diols

We wish to describe here the diastereoselective reaction between chiral N-Boc-α-amino aldehydes with both achiral allyltrichlorostannanes leading to 1,2-syn-N-Boc-α-amino alcohols, which are easily converted to the corresponding 4-N-Boc-amino-3-hydroxy ketones after treatment with catalytic amounts of OsO₄ in the presence of NaIO₄. After reduction of the carbonyl function, these 4-N-Boc-amino-3-hydroxy ketones were converted to 1-deoxy-5-hydroxy sphingosine analogues.     

An efficient method for the preparation of alkylidenecyclopropanes

Yields obtained from Wittig reactions with cyclopropylidenetriphenylphosphorane are greatly improved by addition of the phase-transfer catalyst, TDA-1.     

An efficient new enzymatic method for the preparation of β-aryl-β-amino acid enantiomers

An efficient synthesis of β-aryl-β-amino acid enantiomers has been developed via the lipase-catalysed enantioselective hydrolysis of the corresponding racemic ethyl esters in an organic solvent. High enantioselectivities (E >100) were observed when the lipase PS-catalysed reactions were performed with H₂O (0.5 equiv) in diisopropyl ether at 45 °C. The products could be easily separated and were obtained in good yields of 40%.     

An improved procedure for the synthesis of 2-methoxyisobutylisonitrile: An efficient complexing agent for99mTc

^99mTc hexakis (2-methoxyisobutylisonitrile) is a cationic complex useful as a myocardial perfusion agent. The synthesis of 2-methoxyisobutylisonitrile (MIBI) by a modified and improved procedure in a two-step process with an overall yield of 53% is described. The preparation of its copper and technetium-99m complexes is also presented.     

An effective procedure for the preparation of 3-substituted-4- or 6-azaindoles from ortho-methyl nitro pyridines

3-Substituted-4- and 6-azaindoles were prepared from ortho-methyl-nitropyridines in a practically convenient, one-pot process based on the Leimgruber-Batcho reaction. The procedure comprises a sequence of (a) condensation of an ortho-methyl-nitropyridine with N,N-dimethylformamide dimethyl acetal; (b) alkylation or acylation of the enamine intermediate; (c) reduction of the nitro group to an aniline with in situ cyclization and elimination of dimethylamine to generate the 3-substituted azaindole heterocycle.     

An efficient procedure for the oxidation of fluorinated carbinols

The oxidation of di and trifluorocarbinols has been accomplished in high yields using the Dess-Martin periodane oxidant.     

RuCl3·3H2O as catalyst for Ferrier rearrangement: an efficient procedure for the preparation of pseudoglycosides

By using RuCl₃·3H₂O as catalyst, an improved method for the synthesis of 2,3-unsaturated-glycosides has been established. A series of 2, 3-unsaturated-glucosides were obtained from 2,4,6-tri-O-acetyl-d-glucal or 3,4-di-O-acetyl-6-deoxy-l-glucal in good yield and high anomeric selectivity.     

An efficient and facile procedure for synthesis of octyl polyglucoside

Nonionic surfactant alkyl polyglucoside (APG) was prepared by direct glycosidation of alkyl alcohol with glucose in the presence of sulfate acid-silica gel (H_2SO_4/SiO_2) as solid acidic catalyst.The quantity of catalyst was only of 1 wt%,based on the glucose,and the conversion of glucose was close to 100% at 110℃in 1.5h.The product was characterized by FT-IR,mass and ~1H NMR spectra.The degree of polymerization (DP) of the glucose in the product was 1.37,and critical micelle concentration (CMC) of product was only 0.0104 wt%.     

An efficient protein preparation for proteomic analysis of developing cotton fibers by 2-DE

Preparation of high-quality proteins from cotton fiber tissues is difficult due to high endogenous levels of polysaccharides, polyphenols, and other interfering compounds. To establish a routine procedure for the application of proteomic analysis to cotton fiber tissues, a new protocol for protein extraction was developed by optimizing a phenol extraction method combined with methanol/ammonium acetate precipitation. The protein extraction for 2-DE was remarkably improved by the combination of chemically and physically modified processes including polyvinylpolypyrrolidone (PVPP) addition, acetone cleaning, and SDS replacement. The protocol gave a higher protein yield and vastly greater resolution and spot intensity. The efficiency of this protocol and its feasibility in fiber proteomic study were demonstrated by comparison of the cotton fiber proteomes at two growth stages. Furthermore, ten protein spots changed significantly were identified by MS/tandem MS and their potential relationships to fiber development were discussed. To the best of our knowledge, this is the first time that a protocol for protein extraction from cotton fiber tissues appears to give satisfactory and reproductive 2-D protein profiles. The protocol is expected to accelerate the process of the proteomic study of cotton fibers and also to be applicable to other recalcitrant plant tissues.     

An improved procedure for the preparation of 8-substituted guanines

The preparation of 8-substituted guanines using a new phosphorus(III)-mediated cyclisation of 4-acylamino-5-nitrosopyrimidines as the key step is described.