First enantioselective reductive amination of α-fluoroenones

From α-fluoroenones 2, a synthesis of (E) ketone oxime O-alkyl ethers 5 is reported with good to excellent yields. Then the first enantioselective reduction of these ketimines, via oxazaborolidine, is described with moderate to good enantiomeric excesses, leading to valuable chiral fluoroallylic amines 1.     

Synthesis,Spectroscopic, and Structural Properties of Organogermanyl(IV) Complexes of Pyridine Oximes

Abstract

Reactions of triorganogermanyl(IV) chlorides and diorganogermanyl(IV) dichlorides with sodium salts of pyridine-2-carbaldehyde oxime and 2-acetylpyridine oxime, respectively, in 1:1 and 1:2 molar ratio produced organogermanyl(IV) oximates. All the derivatives have been characterized by spectroscopic techniques and tetrahedral structures have been proposed on the basis of spectroscopic data and molecular orbital calculations.     

Hexamethyldisilathiane in Novel Chemical Transformations: Concept of “Counterattack Reagent”

Abstract

Deliberate design on utilization of each moiety in the “counterattack reagent,” Me₃SiSSiMe₃, allows it to accomplish multistep chemical transformations in one flask.     

Assessment of the Full Compatibility of Copper(I)-Catalyzed Alkyne-Azide Cycloaddition and Oxime Click Reactions for bis-Labelling of Oligonucleotides

The conjugation of oligonucleotides with reporters is of great interest for improving their intrinsic properties or endowing new ones. In this context, we report herein a new procedure for the bis-labelling of oligonucleotides through oxime ligation (Click-O) and copper(I)-catalyzed alkyne–azide cycloaddition (Click-H). 5′-Azido and 3′-aldehyde precursors were incorporated into oligonucleotides, and subsequent coupling reactions through Click-O and Click-H (or vice versa) were successfully achieved. In particular, we exhaustively investigated the full compatibility of each required step for both tethering strategies. The results demonstrate that click Huisgen and click oxime reactions are fully compatible. However, whilst both approaches can deliver the targeted doubly conjugated oligonucleotide, the route involving click oxime ligation prior to click Huisgen is significantly more successful. Thus the reactions investigated here can be considered to be key elements of the chemical toolbox for the synthesis of highly sophisticated bioconjugates.     

Synthesis of 1,3,4-oxadiazoles from the reaction of N-isocyaniminotriphenylphosphorane (NICITPP) with cyclohexanone,a primary amine and an aromatic carboxylic acid via intramolecular aza-Wittig reaction of in situ generated iminophosphoranes

The 1:1 imine intermediate generated by the addition of a primary amine to cyclohexanone trapped by N-isocyaniminotriphenylphosphorane (NICITPP) in the presence of aromatic carboxylic acids and the corresponding iminophosphorane intermediate was formed. Disubstituted 1,3,4-oxadiazole derivatives are formed via intramolecular aza-Wittig reaction of the iminophosphorane intermediate. The reactions were completed in neutral conditions at room temperature (18-26°C). The disubstituted 1,3,4-oxadiazole derivatives were produced in excellent yields.     

Crystal and Molecular Structure of 4-Phenyl-cyclohexanone Semicarbazone

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Stereoselective Synthesis of (Z)-2-Acylamido-4-phenylcrotonates

Stereospecificsynthesisof(Z)-a,o-dehydroaminoacidsisofgreatimportanceinthepreparationofuncommonornatUralopticallypureaminoacids,because,ingeneral,(Z)-isomersaffordmuchhigherenantioselectivitieswithfasterratesthan(E)-isomersinthecatalyticasymmetrichydrogenation'.(Z)-isomersofethyl2-acylamido-4-phenylcrotonate2areimpoFtantprecursorsinthecourseofoursynthesisofL-homopheny1alaninel,akeysynthonformostcommerciallyimportantantihypertensiveACEinhibitorssuchasEnalapril,Benazepril,Lisinopril.Hereinwe…     

Simultaneous quantitation of mono-, di-and trisaccharides as their TMS ether oxime derivatives by GC-MS: I. In model solutions

Summary This paper describes the separation and quantitation of mono- di- and trisaccharides in model solutions. Optimized conditions for identification and determination of common sugar constituents in several natural matrices by GC-MS, from one solution by one injection, are given. Applying a 52 min temperature program to a 30 m capillary column and taking advantage of the stable ratios of the syn- and anti oximes eluting either alone or together with one or two other anomers: provides the basis of calculation for co-eluting compounds. Saccharides (5–200 ng), such as fructose, glucose, sucrose, trehalose, cellobiose, maltose, turanose, gentiobiose, palatinose, melibiose, isomaltose, erlose, raffinose, melezitose, maltotriose, panose and isomaltotriose, in the presence of each other in various ratios, have been measured as silyloxime compounds with a reproducibility of ≤5 R.S.D. %. The possibility of measuring all these saccharides as their TMS methoximes is also presented. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996.