To explore the role of hydrophobic interaction in the stereoselective solvolyses of optically active activated esters by polymeric imidazoles, N-methacryloyl-L-histidine methyl ester(1) and N-methacryloyl-L-phenylalanyl-L-histidine methyl ester(2) were synthesized and copolymerized with N,N-dimethyl-N-hexadecyl-N-(11-methacryloyloxyundecanyl)ammonium bromide (I), N,N-dimethyl-N-hexadecyl-N-[10-(p-vinylcarboxanilido) decyl] ammonium bromide (II), and N,N-dimethyl-N-hexadecyl-N-[10-(p-methacryloyloxyphenoxycarbonyl) decyl] ammonium bromide (III) to obtain imidazole-containing polymeric surfactants. In the presence of each of these copolymers the stereoselective solvolytic reactions of N-carboethyoxy-D- and L-phenylalanine p-nitrophenyl esters (D-NEP and L-NEP), N-carbobenzoxy-D- and L-phenylalanine p-nitrophenyl esters (D-NBP and L-NBP), N-dodecanoyl-D- and L-phenylalanine p-nitrophenyl esters (D-NDP and L-NDP), and D- and L- $\alpha$-methoxyphenylacetic acid p-nitrophenyl esters (D-Man-PNP and L-Man-PNP) were carried out.
In the solvolyses of D-NBP and L-NBP by copoly (I-1), copoly (II-1), copoly (III-1), and copoly(I-2), polymeric catalysts exhibited not only increased catalytic activity but also enhanced enantioselectivity as the mole % of surfactant monomers in all the copolymers increased, indicating that hydrophobic interaction can be one of the most limportant contributions to the high catalytic activity and enantioselectivity.
In the solvolyses of activated esters of different alkyl sizes, the polymeric catalysts showed enhanced enantioselective solvolyses toward the more hydrophobic substrates, D-NBP and L-NBP, while in the case of solvolyses of D- and L-NEP and Man-PNP, there was no significant differences between the catalytic rate constants for two enantiomeric substrates.
The hydrophobic interaction was temperature dependent. As the reaction temperature was lowered for the solvolyses of D- and L-NBP with catalyst polymer, copoly (II-1), the reaction rate increased and enhanced enantioselectivity was observed.
The coaggregate systems of copoly(I-1) and micellar surfactants such as Triton X-100, CDEAB, and SDS, were prepared and introduced into the solvolyses of optically active esters. The polymeric imidazoles exhibited the different catalytic activity and enantioselectivity according to the micellar surfactant employed, and in the case of coaggregate system of 70 mole % of CDEAB and 30 mole % of II showed enhanced enantioselective catalysis.
The aggregate morphology of imidazole-containing polymeric surfactants in the sonicated solvolytic solutions was investigated by the turbidity and electron micrographs. Some of the solvolytic systems employed have large extended ordered aggregate with the diameter of 200-600 nm, which appears to be large multilayered vesicles. From these results concluded is that hydrophobic interaction in ordered aggregate structure plays important role in enantioselective catalysis of optically active imidazole-containing polymers.
고분자 이미다졸에 의한 광학활성에스테르의 입체선택적 가수분해에 있어서 소수성상호작용의 역할을 연구하기 위하여 N-메타크릴로일-L-히스티딘 메틸에스테르(1)와 N-메타크릴로일-L-페닐알라닐-L-히스티딘 메틸에스테르(2)를 합성한 다음 N, N-디메틸-N -헥사데실-N-( 11-메타크릴로일옥시운데카닐) 암모늄 브로마이드(I), N, N-디메틸-N-헥사데실-N-[10-(P-비닐카르복사닐리도) 데실] 암모늄 브로마이드(II). N, N-디메틸-N-헥사데실-N-[10-(P-메타크릴로일옥시 페녹시카르보닐)데실] 암모늄 브로마이드 (III)와 공중집합시켜 이미다졸을 갖는 고분자 계면활성제들을 합성했다. 이 고분자 촉매 존재하에서 N-카르보에톡시-D-와 L-페닐알라닌 p-니트로페닐 에스테르(D-NEP와 L-NEP), N-카르 보벤족시-D-와 L-페닐알라닌 p-니트로페닐 에스테르(D-NBP와 L-NBP), N-도데카닐-D-와 L-페닐알라닌 p-니트로 페닐에스테르(D-NDP와 L-NDP), D-와 L-$\alpha$-메톡시 페닐아세트산 p-니트로페닐 에스테르(D-Man-PNP와 L-Man-PNP)에대한 가수분해 반응을 실시하였다.
I과 1, II와 1, III과 1, 그리고 I과 2의 공중합체에 의한 D-NBP와 L-NBP의 가수분해에서 공중합체 내의 계면활성제 단량체의 몰%가 증가함에 따라 촉매활성도 및 L-형태의 기질에 대한 입체선택성이 증가하였다. D-와 L-NEP 및 Man-PNP를 기질로 사용하였을 때는 두 광학이성질체 사이의 가수분해 속도차이는 보이지 않았다. 더 소수성인 D-NBP 및 L-NBP의 경우에는 촉매활성이 증가하였으며 뚜렷한 입체선택성이 나타났다. 온도에 따른 소수성상호작용의 변화에 의해 온도가 낮아질수록 반응속도가 증가하였고 입체선택성도 증가하였다. 고분자계면활성제 촉매에 대한 미셀 계면활성제의 영향은 사용한 종류에 따라 달랐다. CDEAB 70몰%와 II 30몰%의 경우에 입체선택성이 증가하였다. 가수분해반응 용액에서의 이미다졸을 갖는 고분자계면활성제의 구조를 혼탁도 측정 및 전자현미경 사진을 통해 관찰하였다. 사용한 가수분해 계에 따라서 200-600nm의 직경을 갖는 규칙적인 집합체의 형태를 볼 수 있었다. 이상의 결과로 볼 때 기질과 고분자촉매 사이의 소수성 상호작용이 입체선택적 가수분해에 중요한 역할을 하고 있음을 알 수 있었다.
