Junzo Yamashita

High-performance liquid chromatographic separation of enantiomers on axially chiral binaphthalene derivatives bonded to silica gel

Preparation de 3 nouvelles phases stationnaires chirales comportant des unites acides binaphtalene carboxyliques liees chimiquement a des gels de silice silanises avec amino-3 propyle ou amino-11 undecyle

Chiral stationary phases consisting of axially dissymmetric 2′-substituted-1,1′-binaphthyl-2-carboxylic acids bonded to silica gel for high-performance liquid chromatographic separation of enantiomers

Abstract Seven chiral stationary phases (CSPS) were prepared by bonding axially dissymmetric 2′-substituted-1,1′- binaphthyl-2-carboxylic acids to aminoalkylsilanized silica gels through an amide linkage, and the effect of the 2′-substituents (CN, COOH, CONH 2 , CONHEt, CONEt 2 and OCH 3 ) was investigated for the high-performance liquid chromatographic (HPLC) separation of enantiomers. Among these CSPS, that which had a 2′-carboxyl substituent showed the best performance and efficiently discriminated several enantiomeric amino acids, amines and alcohols as their 3,5-dinitrophenyl derivatives, and biaryls bearing 2,2′-polar substituents, by normal-phase HPLC. Stereoselective π-donor-acceptor interaction and dipole stacking interaction between the CSPs and the analytes seem to play a critical role in the enantioseparation.

Chiral Recognition Properties of Chiral 18-Crown-6 Ethers with Aromatic Substituents

The chiral recognition properties of chiral 18-crown-6 ethers with phenyl, 1-naphthoxymethyl, 1-naphthylmethyl, or 2,3,5,6-tetramethylphenylmethyl substituents for α-phenylglycine methyl ester and 1-phenylethylamine perchlorate were investigated by a standard extraction procedure. The chiral recognition factor of 1-naphthoxymethyl substituted crown ether is 2.0 for the former salt but near 1.0 for the latter, whereas that of the other crown ethers is not so dependent on the structure of salts, which indicates the importance of the mutual relation of the structure of host and guest molecules.

Thermal Decomposition of Metal Salts of Carboxylic Acids

カルボン酸金属塩の熱分解機構を総合的に整理し検討する研究の一環として, 5 種類の脂肪酸の1 1 種類の金属塩の熱分解反応をしらべた。金属塩の熱分解開始温度は, 金属の電気陰性度が増加するほど, また脂肪酸の炭素数が減少するほど, 低くなる傾向にある。また, アルカリ金属塩, アルカリ土類金属塩からはケトンのみが生成するが, 重金属の塩からは, ケトンの他に酸および酸無水物が生成する。これらの事実は, 標準状態における熱力学的計算の結果と傾向がよく一致し, 金属の酸化物と炭酸塩との相対的な安定性が熱分解生成物の種類を規定する重要な因子であることを示唆するものであり, 金属の脱離を律速段階とする4 員環遷移状態を含む求核的な機構でよく説明される。また酸無水物がケトン生成の中間体であると考える説は否定される。