생분해성 고분자를 위한 에스터로 연결된 아미노산-당 알코올 콘쥬게이트의 효소적 합성

학위논문(박사) - 한국과학기술원 : 화학공학과, 2001.8, [ vii, 124 p. ]Commercial lipases and proteases were tested for the selective acylation of monosaccharides and sugar alcohol through the transesterification of activated amino acid esters. A commercialized protease from Bacillus licheniformis, Optimase M-440 showed the highest catalytic activity in the transesterification of N-t-Boc-L-Phe-OTFE with D-glucose and D-sorbitol. The broad substrate specificity of Optimase M-440 was effective for the acylation of monosaccharides and sugar alcohols with various amino acid esters. Trifluoroethyl ester of L-phenylalanine was more effective for the transesterification than trichloroethyl ester, cyanomethyl ester and oxime ester. Various solvents were tested for the transesterification with Optimase M-440 as a reaction medium. Optimase M-440 catalyzed the highest conversion in pyridine among the tested organic solvents. Optimase M-440 showed a broad substrate specificity towards trifluoroethyl esters of amino acids and the transesterification of L-form of phenylalanine was faster than D-form. Optimase M-440 exhibited a preferable catalytic activity on the primary hydroxyl group of monosaccharides and sugar alcohols and the regioselectivity was confirmed by the $^13C-NMR$ of the conjugates of amino acid and saccharides. The acylation occurred at the primary hydroxyl groups of D-glucose, and regioselectivity and chemoselectivity of Optimase M-440 was observed in acylation of D-glucosamine. Optimase M-440 catalyzed the acylation of two primary hydroxyl groups of sugar alcohols in spite of the change of reaction conditions. Sugar alcohol conjugates of N-t-Boc-L-Phe-OTFE and N-t-Boc-L-Met-OTFE were synthesized without the acylation of secondary hydroxyl groups. In the transesterification of Nα, Nε-di-t-Boc-L-Lys-OTFE$ and N-t-Boc-L-Asp-diOTFE, Optimase M-440 did not discriminate the glycosidic hydroxyl groups. Only when the glycosidic -OH was blocked, Optimase M-440 could selectively catalyze the acylation of primary hydroxyl group without o...한국과학기술원 : 화학공학과

트리알킬실릴 트리플레이트에 의한 엔아민 유도체와 엔올 실릴 에테르의 α,β-불포화카르보닐 화합물들에 대한 콘쥬게이션 첨가 반응

학위논문(석사) - 한국과학기술원 : 화학과, 1997.2, [ iii, 64 p. ]한국과학기술원 : 화학과

Lipase를 이용한 피마자유의 methanolysis

피마자유와 메탄올의 transesterification 반응 (methanolysis)에서 Novozym 435가 가장 좋은 활성을 나타냈다. Novozym 435의 경우 유기용매를 사용하지 않을 경우에도 좋은 활성을 유지하였고 사용되는 효소량에 따라 최적의 유기용매가 다르다는 것을 확인하였다. 0.5 wt% Novozym 435를 사용한 경우 DIPE를 사용하였을 매 가장 높은 활성을 나타내었으나, 1.0 wt% 의 경우에는 heptane을 이용하였을 때 가장 높은 활성을 보였다. Novozym 435를 이용한 피마자유의 methanolysis에서 methanol 에 의한 저해 반응이 나타나고 oil과 methanol의 몰 비 가 약 1:7.37 일 경우 최대의 ricinoJeic acid methyl ester 를 얻을 수 있었다. 1.0wt%의 Novozym 435를 이용한 methanolysis를 통하여 하루동안 피마자유로부터 ricinoleic acid methyl ester 를 86.1% 의 수율로 얻을 수 있었다

Enzymatic synthesis of ester0linked conjugates of amino acid and monosaccharide

In this study the enzymatic synthesis of ester-linked conjugates of amino acid and monosaccharide in pyridine was tested by the catalysis of Optimase M-440, an alkaline serine pretense. Optimase M-440 showed the higher activity in the reaction of monosaccharides which have one or more primary -OH groups. And also Optimase M-440 showed high regioselectivity; The transesterification of primary -OH group selectively occurred