Yuko Yamashoji

Chiral recognition and enantiomeric separation of alanine β-naphthylamide by cyclodextrins

Abstract The host-guest interaction of chemically unmodified and modified (methylated and acetylated) cyclodextrins (CDs) with alanine β-naphthylamide was studied by 1 H NMR spectrometry. The inclusion complex formation of the guest with CDs, except for α-CD, was evaluated on the basis of remarkable changes in their chemical shifts. The chiral recognition of dl -alanine β-naphthylamide by CDs was confirmed from duplication of its proton resonances. The enantiomeric separation ability of CDs was also investigated by capillary zone electrophoresis. Diacetylated β-CD and unmodified β- and γ-CDs exhibited high enentioselectivities. Moreover, the chemical modification produced a reverse in the migration order of the enantiomers.

Enantiomeric separation of dansylamino acids by capillary zone electrophoresis based on complexation with cyclodextrins

SummaryThe enantiomeric separation ability of unmodified and methylated cyclodextrins (CDs) during capillary zone electrophoresis (CZE) was investigated using twelve dansylamino acids. Unmodified β- and γ-CDs exhibited high enantioselectivities. α-CD could scarcely separate the enantiomers before and after dimethylation, but obtained enantioselectivity after trimethylation. On the other hand, dimethylation of β-CD removed much of its high enantioselectivity. Moreover, the chemical modifications produced a reverse in the migration order of the enantiomers. The inclusion of dansyl-DL-phenylalanine with CDs was evaluated using 600 MHz 1H NMR spectroscopy.

Preparation of an anion-exchange resin with quaternary phosphonium chloride and its adsorption behaviour for noble metal ions

Abstract An anion-exchange resin was prepared by the reaction of chloromethylated polystyrene with tris(2,6-dimethoxyphenyl)phosphine. It possesses high sorption selectivity for noble metal ions such as gold(III) and platinum(IV). In addition, complete separation between gold(III) and copper(II) was achieved from hydrochloric acid solution with this resin using a column system.

Ion-pair extraction of the gallium(III) ion from hydrochloric acid with various methoxy-substituted triarylphosphines

Abstract A series of methoxy-substituted triarylphosphines RnPh3-nP (n = 1−3), where R may be 2-(MeO)C6H4,4-(MeO)C6H4,2,6-(MeO)2C6H3 and 2,4,6-(MeO)3C6H2, have been prepared and employed as extractants for the gallium(III) ion from hydrochloric acid solutions. The extractabilities of these compounds are found to become more effective with an increase in their basicities, which are determined by non-aqueous titrimetry. Highly basic compounds, {(2,6-(MeO)2C6H3)}3P and {(2,4,6-(MeO)3C6H2)}3P, possess the highest extractability amongst the triarylphosphines. The extraction mechanism is discussed on the basis of the 1H and 31P NMR spectroscopic data.

NMR study of the conformational changes of dibenzo-22-crown-6 ether by complexation with thallium(I) and potassium(I) ions in solution

Abstract The higher selectivity towards a thallium(I) ion of dibenzo-22-crown-6 (DB22C6) compared with dibenzo-18-crown-6 (DB18C6) and dibenzo-20-crown-6 (DB20C6) was investigated by 1 H and 13 C NMR spectroscopy and 13 C relaxation time ( T 1 ) measurements. The results indicate that DB22C6 has a much larger cavity than the ionic radii of univalent metal ions such as thallium(I) and potassium(I). Therefore, its conformational change by complexation with the metal ions should be larger than those of DB18C6 and DB20C6, and the conformational change in DB22C6 by complexation with a potassium(I) ion is larger than with a thallium(I) ion.

Liquid-liquid extraction of metal ions with tris (2,6-dimethoxyphenyl) phosphine and its quaternary phosphonium salts

Abstract The extraction of various metal ions from hydrochloric acid solutions with tris(2,6-dimethoxyphenyl)phosphine, [2,6-(MeO) 2 C 6 H 3 ] 3 P, abbreviated to (2,6-MeOPh) 3 P, and its tertiary and quaternary phosphonium salts were studied. A series of phosphonium salts, [(2,6-MeOPh) 3 PH] + ClO − 4 , [(2,6-MeOPh) 3 PR] + Br − and {[(2,6-MeOPh) 3 P] 2 R′} 2+ (Br − ) 2 , where R = C 12 H 25 , C 18 H 37 or C 6 H 5 CH 2 and R′ = p -CH 2 C 6 H 4 CH 2 , (CH 2 ) 3 and (CH 2 ) 10 , were synthesized and applied to an anion exchanger for chloro complex anions of various metal ions. (2,6-MeOPh) 3 P and [(2,6-MeOPh) 3 PR] + Br − were found to be effective for the extraction of metal ions such as iron(III), gold(III) and gallium(III), forming tetrachloro complex anions of the M III Cl − 4 type. The extractabilities of the doubly charged cationic quaternary phosphonium salts [{(2,6-MeOPh) 3 P} 2 R′] 2+ (Br − 2 , were found to be superior to those of the singly charged cationic phosphonium salts for metal ions such as cadmium(II), platinum(II) and palladium(II), forming a tetrachloro complex doubly charged aion of the M II Cl 2− 4 type. Most of the metal ions are extracted through ion-pair formation between their chloro complex anions and the phosphonium cations.

Extraction of molybdenum(vi) by bis-(dioctylphosphinyl)-alkanes

Abstract A series of bis-(dioctylphosphinyl)-alkanes [(DOPO) 2 R], has been prepared and employed as liquid-liquid extractants for molybdenum(VI) from hydrochloric acid solutions [R = p -CH 2 C 6 H 4 CH 2 or (CH 2 n ( n = 2, 3, 4, 5, 8 or 10)]. These bis-type ligands were found to be much more efficient extractants than trioctylphosphine oxide and benzyl-dioctylphosphine oxide. The formula of the molybdenum(VI) extracted by (DOPO) 2 (CH 2 ) 5 into the organic phase was determined to be MoO 2 [(DOPO) 2 (CH 2 ) 5 ](Cl) 2 .