A rule to predict which enantiomer of a secondary alcohol reacts faster in reactions catalyzed by cholesterol esterase, lipase from Pseudomonas cepacia, and lipase from Candida rugosa
摘要:
The enantioselectivity of the title enzymes for more than 130 esters of secondary alcohols is correlated by a rule based on the sizes of the substituents at the stereocenter. This rule predicts which enantiomer of a racemic secondary alcohol reacts faster for 14 of 15 substrates of cholesterol esterase (CE), 63 of 64 substrates of lipase from Pseudomonas cepacia (PCL), and 51 of 55 cyclic substrates of lipase from Candida rugosa (CRL). The enantioselectivity of CRL for acyclic secondary alcohols is not reliably predicted by this rule. This rule implies that the most efficiently resolved substrates are those having substituents which differ significantly in size. This hypothesis was used to design syntheses of two chiral synthons: esters of (R)-lactic acid and (S)-(-)-4-acetoxy-2-cyclohexen-1-one, 70. As predicted, the acetate group of the methyl ester of lactyl acetate was hydrolyzed by PCL with low enantioselectivity because the two substituents, CH3 and C(O)OCH3, are similar in size. To improve the enantioselectivity, the methyl ester was replaced by a tert-butyl ester. The acetate group of the tert-butyl ester of lactyl acetate was hydrolyzed with high enantioselectivity (E > 50). Enantiomerically pure (R)-(+)-tert-butyl lactate (> 98% ee, 6.4 g) was prepared by kinetic resolution. For the second example, low enantioselectivity (E < 3) was observed in the hydrolysis of cis-1,4-diacetoxycyclohex-2-ene, a meso substrate where the two substituents, CH2CH2 and CH = CH, are similar in size. To improve enantioselectivity, the size of the CH = CH substituent was increased by addition of Br2. The new substrate was hydrolyzed with high enantioselectivity (E > 65) using either CE or CRL. Enantiomerically pure 70 (98% ee) was obtained after removal of the bromines with zinc and oxidation with CrO3/pyridine.
Transesterification/Acylation of Secondary Alcohols Mediated by N-Heterocyclic Carbene Catalysts
摘要:
N-Heterocyclic carbenes (NHC) are efficient catalysts for transesterification/acylation reactions involving secondary alcohols. The catalytic transformations are carried out employing low catalyst loadings in convenient reaction times at room temperature.
Chlorotrimethylsilane Catalysed Acylation of Alcohols<sup>1</sup>
作者:R. Kumareswaran、Anuradha Gupta、Yashwant D. Vankar
DOI:10.1080/00397919708005028
日期:1997.1
A variety of alcohols are converted into the corresponding acetates upon treatment with acetic anhydride and catalytic amount of chlorotrimethylsilane in acetonitrile (or dichloromethane).
在乙腈(或二氯甲烷)中用乙酸酐和催化量的三甲基氯硅烷处理后,多种醇转化为相应的乙酸酯。
Iron (III) Phosphate as a Green and Reusable Catalyst Promoted Chemo Selective Acetylation of Alcohols and Phenols with Acetic Anhydride Under Solvent Free Conditions at Room Temperature
作者:F.K. Behbahani、M. Farahani、H.A. Oskooie
DOI:10.5012/jkcs.2011.55.4.633
日期:2011.8.20
알코올과 페놀 계 화합물을 아실화시키는 반응에서, iron (III) phosphate 촉매를 사용했을 때에, 좋은 수율로 아실화 화합물을 얻었다. Iron (III) phosphate 촉매는 또한 친환경 반응에 재사용할 수 있는 친환경 촉매이다.
Iron (III) phosphate was employed as an efficient catalyst for the chemo selective acetylation of alcohols and phenols under solvent free condition at room temperature and with high yields. Iron (III) phosphate is also a potential green catalyst due to solid intrinsically, reusable and with high catalytic activity.
Method for producing organic compounds by substituting halogen atoms
申请人:MITSUI CHEMICALS, INC.
公开号:EP1486479A1
公开(公告)日:2004-12-15
The invention pertains to a method in which a halogen atom of an organic compound is replaced with a group derived from a nucleophilic agent, at high yield and high efficiency, by the following method which includes a step of reacting the nucleophilic agent with an organic material having a halogen atom bonded to a carbon atom having four σ bonds, more specifically: a method for producing an organic compound having Q, the method including a step of reacting a compound represented by general formula (2) with an organic starting material having at least one halogen atom bonded to a carbon atom having four σ bonds so as to replace the halogen atom in the organic starting material with Q:
MQa (2)
(wherein M represents an alkali metal atom, an alkali earth metal atom, or a rare earth metal atom; Q represents a moiety of an inorganic acid or an active hydrogen compound derived by eliminating a proton, wherein Q is a halogen atom different from the halogen atom in the organic starting material having the halogen atom bonded to the carbon atom having the four σ bonds; and a represents an integer of 1 to 3) in the presence of a compound represented by general formula (1)
(wherein Z- represents an anion derived by eliminating a proton from an inorganic acid or an active hydrogen compound; R2 is the same or different; R2 each independently represent a C1-C10 hydrocarbon group or two R2 on the same nitrogen atom may be bonded with each other to form a ring with the nitrogen atom).
Pharmaceutical formulations and methods of treatment using the same
申请人:Malcolm A. Bruce
公开号:US20070010431A1
公开(公告)日:2007-01-11
Pharmaceutical formulations containing at least one compound of Formulae I-XXVI herein and at least one surfactant. Pharmaceutically acceptable carriers and excipients may also be included in the formulations. The formulations of the present invention are suited for use in single unit dosages.
Meerwein–Ponndorf–Verley-type reductive acetylation of carbonyl compounds to acetates was successfully carried out in the presence of isopropenylacetate under the influence of a catalytic amount of Ln(OiPr)3 at room temperature. Various carbonyl compounds were converted into the corresponding acetates in fair to good yields.
在室温下,在催化量Ln(O i Pr)3的影响下,在乙酸异丙烯酯的存在下,成功实现了Meerwein-Ponndorf-Verley型羰基化合物还原为乙酸的乙酰基化反应。各种羰基化合物均以适当的收率转化为相应的乙酸盐。