Determination of α‐hydroxy acids and their enantiomers in fruit juices by ligand exchange CE with a dual central metal ion system

The content of α‐hydroxy acids and their enantiomers can be used to distinguish authentic and adulterated fruit juices. Here, we investigated the use of ligand exchange CE with two kinds of central metal ion in a BGE for the simultaneous determination of enantiomers of dl ‐malic, dl ‐tartaric and dl ‐isocitric acids, and citric acid. Ligand exchange CE with 100 mM d ‐quinic acid as a chiral selector ligand and 10 mM Cu(II) ion as a central metal ion could enantioseparate dl ‐tartaric acid but not dl ‐malic acid or dl ‐isocitric acid. Addition of 1.8 mM Sc(III) ion to the BGE with 10 mM Cu(II) ion to create a dual central metal ion system permitted the simultaneous determination of these α‐hydroxy acid enantiomers and citric acid. The proposed ligand exchange CE was thus well suited for detecting adulteration of fruit juices.     

Synthesis of the Immunodominant Trisaccharide Related to the Antigen From E. COLI O 126

The trisaccharide derivative methyl 2-O-[4,6-di-O-acetyl-3-O-(2,3,4,6-tetra-O-benzyl-α-D-gal-actopyranosyl)-2-deoxy-2-phthalimido-β-D-gluco-pyranosyl]-4,6-O-benzylidene-β-D-mannopyranoside (12) was obtained when 3-O-(2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl)-4,6-di-Oacetyl-2-deoxy-2-phtha-limido-β-D-glucopyranosyl trichloroacetimidate (8) was allowed to react with methyl 3-O-benzyl-4,6-O-benzylidene-β-D-mannopyranoside (11) in presence of trimethylsilyl triflate. Removal of protecting groups then gave the desired trisaccharide.     

Synthesis of the 1-hydroxy-closo-decaborate anion [1-B10H9OH]

Reactions of the diazonium derivative of closo-decaborate anion with oxygen nucleophiles were studied. The reaction of [1-B₁₀H₉N₂]⁻ with hydroxide ion gives the corresponding hydroxy derivative [1-B₁₀H₉OH]²⁻ in high yield. The reactions with OR (R = Me, Et, i-Pr, Ph) result in mixture of [1-B₁₀H₉OR]²⁻ and [a²-B₂₀H₁₈]⁴⁻.     

Synthetic applications of ethyl 3-bromodifluoromethyl-3-benzyloxy-acrylate as a gem-difluorination building-block: Its reactions with aldehyde and epoxide

Synthetic applications of ethyl 3-bromodifluoromethyl-3-benzyloxy-acrylate as a versatile and multifunctionalized gem-difluorination building block to introduce difluoromethene subunit into some new hydroxy esters have been investigated. It was found that its zinc mediated reaction with a variety of aldehyde in DMF gave the Reformatsky reaction mode product, β-hydroxy ester, in good yield, while its tetrakis(dimethylamino)ethylene (TDAE) promoted reaction with a limited scope of aldehyde produced Barbier reaction mode product, δ-hydroxy ester, in moderate yield. The reaction of its zinc reagent with styrene oxide resulted in rearrangement of the epoxide to 2-phenyl-acetaldehyde, and then the zinc reagent condensed with this aldehyde to provide the Reformastsy reaction type product, β-hydroxy ester, in low yield.     

Synthesis,Crystal Structure and Characterization of Hexakis[2‐methoxy‐4‐formylphenoxy]cyclotriphosphazene

The new cyclotriphosphazene derivative N₃P₃(OC₆H₃OCH₃COH)₆ ( 1 ) was synthesized from hexachlorocyclotriphosphazene, N₃P₃Cl₆, and 4‐hydroxy‐3‐methoxybenzaldehyde in acetonitrile in the presence of K₂CO₃. The structure of 1 was verified by means of elemental analysis, IR, ¹H NMR, ¹³C NMR, ³¹P NMR spectra, thermal analysis and X‐ray diffraction.     

Stereoselective synthesis ofvic-halohydrins and an unusual Knoevenagel product from an organocatalyzed aldol reaction：A non-enamine mode

Stereoselective synthesis by an aldol reaction between chloroacetone and aldehyde was studied using a synthesized chiral organocatalyst and triethylamine. The reaction gave α-chloro-β-hydroxy ketones in excellent yield with highantiselectivity and enantioselectivity. The chiral organocatalyst was also used in the Knoevenagel reaction, which gave α-cyano-β-hydroxy ketones at a low tem-perature and the usual Knoevenagel product at a high temperature. Both products were obtained in good to moderate yield with goodanti selectivity in the case of α-cyano-β-hydroxy ketone deriva-tives.     

Carbohydrate Derivative from Baylis–Hillman Adduct. An Easy and Short Synthesis of 2‐Deoxy‐2‐C‐methylene‐D‐erythro‐pentono‐1,4‐lactone

Abstract

A simple and straightforward approach for the synthesis of an α‐methylene‐δ‐butyrolactone from a Baylis–Hillman adduct obtained from a chiral α‐hydroxy aldehyde, is described.     

Stereochemical differentiation and simultaneous analysis of 3-, 4-, and 5-hydroxyalkanoic acids from biopolyesters by multidimensional gas chromatography

The direct enantioselective analysis of 3-, 4-, and 5-hydroxy fatty acids from biological material has been achieved by enantioselective multidimensional gas chromatography (enantio-MDGC) with heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)- or (2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phase. All the bacteria investigated produced polyesters of enatiomerically pure (R) configured compounds.     

Asymmetric dinuclear hydroxyl and ethoxyl citrato dioxovanadates(V)

Asymmetric citrato dioxovanadates(V), [Hneo]₄[V₂O₄(R-Hcit)(OH)][V₂O₄(S-Hcit)(OH)]?·?4H₂O (1) and [Ni(phen)₃]₂[V₂O₄(R-Hcit)(OC₂H₅)][V₂O₄(S-Hcit)(OC₂H₅)]?·?4H₂O (2) and (H₄cit?=?citric acid, neo?=?2,9-dimethyl-1,10-phenanthroline, phen?=?1,10-phenanthroline) are isolated with the help of large counterions. Structural analyses of complexes 1 and 2 show that vanadium atoms are coordinated by tridentate citrate ligand and hydroxy or ethoxy groups, respectively. The insertions of hydroxy and ethoxy groups give new examples of the mixed RO-bridges for vanadium–citrate complexes.