Sugar-amide surfactant micelles as effective reaction fields for enantioselective hydrolysis of alpha-amino acid esters.
The enantioselective hydrolysis of p-nitrophenyl esters of alpha-amino acids (Phe, Leu, Ala) was accomplished in micelles formed with the surfactants bearing one or two sugar-amide headgroups. The effect of structural variations in such sugar-amide surfactants on the rates and enantioselectivity (kD/kL) for hydrolysis of p-nitrophenyl esters of D- and L-phenylalanine hydrogen bromides (D- and L-PheONp) was studied. Both the hydrolysis rate of D-PheONp and the enantioselectivity increased with an increase in the alkyl chain length as well as an increase in the number of the alkyl chains in the maltobionamide-type surfactants. Enantioselectivity also increased with an increase in the sugar chain length from bisgluconamide to bismaltobionamide (by one glucose unit per each sugar chain) in the double-sugar-chain surfactants, but enantioselectivity was no longer influenced by a further increase to bismaltotrionamide. The stereochemistry of the linkage between the sugar units in the sugar chain remarkably affected the enantioselectivity: the maltobionamide-type surfactant, in which the two sugar units are connected by an alpha-1,4-glucosidic linkage, showed high enantioselectivity (kD/kL = 5.5), whereas the surfactant bearing cellobionamide headgroups (beta-1,4-glucosidic linkage) showed no enantioselectivity. Similar trends were observed when p-nitrophenyl esters of D- and L-leucine hydrogen bromides were used as substrates. On the other hand, the rates and enantioselectivity for hydrolysis of p-nitrophenyl esters of D- and L-alanine hydrogen bromides were not so largely affected by the structural variations in the sugar-amide surfactants. Additionally, the effects of the surfactant concentration and the reaction temperature on the rates and enantioselectivity for the hydrolysis of D- and L-PheONp were examined.
Kida
Toshiyuki
T
Department of Molecular Chemistry, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, 565-0871, Japan.
Kajihara
Keisuke
K
Isogawa
Kazuhiko
K
Zhang
Wanbin
W
Nakatsuji
Yohji
Y
Ikeda
Isao
I
Akashi
Mitsuru
M
D000577:Amides / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry* / Q000378:metabolism; D002241:Carbohydrates / Q000737:chemistry*; D004952:Esters / Q000737:chemistry* / Q000378:metabolism; D006868:Hydrolysis; D007700:Kinetics; D008823:Micelles; D015394:Molecular Structure; D013237:Stereoisomerism; D013501:Surface-Active Agents / Q000737:chemistry*
D000577:Amides; D000596:Amino Acids; D002241:Carbohydrates; D004952:Esters; D008823:Micelles; D013501:Surface-Active Agents