One-Pot Direct Conversion of 2,3-Epoxy Alcohols into Enantiomerically Pure 4-Hydroxy-4,5-dihydroisoxazole 2-Oxides
摘要:
[GRAPHICS]A new methodology for the one-pot direct conversion of 2,3-epoxy alcohols into enantiomerically pure 4-hydroxy-4,5-dihydroisoxazole P-oxides 1 has been found. The reaction works at room temperature and can be run at the 5-10 g scale. The mixture of 4,5-cis and 4,5-trans isomers obtained can be separated as such or as the bis-TDS ethers, A preliminary example of reductive cleavage of 1 to the corresponding amino polyol is also reported.
The hydrolytic kineticresolution of five glycidaldehyde acetal derivatives was examined using the recombinant Aspergillus nigerepoxide hydrolase as biocatalyst. This could successfully be performed, at room temperature, using solely demineralised water as solvent and following a two-phase methodology allowing us to operate at a global substrate concentration as high as 200 g/L in the reactor. The
使用重组黑曲霉环氧化物水解酶作为生物催化剂检测了五种缩水甘油醛缩醛衍生物的水解动力学拆分。这可以在室温下成功完成,仅使用软化水作为溶剂,并遵循两阶段方法,使我们能够在反应器中以高达200 g / L的总体底物浓度运行。根据缩醛部分的结构,观察到的E值适中至极好,表明仅通过选择正确的取代基就可以非常有效地实现该拆分。因此,未反应的(R)-环氧化物和形成的(S)-二醇都可以良好或优异的ee获得。(对于环氧化物,ee > 99%)。对于最佳的底物,可通过使用约9至10×10 -4 mol%的底物上的生物催化剂对分子的比率在数小时内进行反应。与化学催化剂相比,该酶的周转频率(TOF)和总周转数(TON)被证明是极好的–分别达到6×10 2 mol sub / mol enz / min和6×数量级的值。 10 4 mol sub / mol enz。最佳(两相)反应器的时空产率因此可以达到高达56
First stereoselective total synthesis and reconfirmation of absolute structure of nonenolide (−)-stagonolide D
The first stereoselective totalsynthesis of nonenolide (−)-stagonolide D has been accomplished. Midland Alpine borane reduction to install hydroxyl group at C4, Henbest epoxidation to introduce epoxide stereoselectively between C7 and C8, Yamaguchi esterification and Olefin metathesis reaction are the key steps involved in the totalsynthesis.
Juliá–Colonna stereoselective epoxidation of some α,β-unsaturated enones possessing a stereogenic centre at the γ-position: synthesis of a protected galactonic acid derivative
作者:Peter C. Ray、Stanley M. Roberts
DOI:10.1039/b007100p
日期:——
The oxidation of enones 6â8 using peroxide or percarbonate and polyleucines as catalysts gave the corresponding diastereomers 9â12 in high yield. The compound 9 was converted into the galactonic acid derivative 16 in five steps and in an overall yield of nearly 60%. Polyleucines are shown to be catalysts powerful enough to overturn the intrinsic stereocontrol in the chosen substrates.
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A stereospecific route to (R)- and (S)-[C-13]-butadiene monoxide was developed using (R)- or (S)-glycidaldehyde and a polymer-supported Wittig reagent. (C) 1997 Elsevier Science Ltd.
A highly selective synthesis of (Z)-α,β-unsaturated ketones
作者:Wensheng Yu、Mei Su、Zhendong Jin
DOI:10.1016/s0040-4039(99)01393-3
日期:1999.9
New Wadsworth-Emmons reagents, bis(2,2,2-trifluoroethyl)-(2-oxopropyl)phosphonate 6 and bis(2,2,2-trifluoroethyl)-(1-methyl-2-oxopropyl)-phosphonate 7 were prepared and their reactions with aldehydes yielded disubstituted and trisubstituted (Z)-alpha,beta-unsaturated ketones. (C) 1999 Elsevier Science Ltd. All rights reserved.