Catalytic Asymmetric Synthesis of Allylic Thiol Derivatives
作者:Larry E. Overman、Scott W. Roberts、Helen F. Sneddon
DOI:10.1021/ol8002942
日期:2008.4.1
The palladium(II) complex [(Rp,S)-COP-Cl]2 and its enantiomer catalyze the rearrangement of linear prochiral O-allyl carbamothioates under mild conditions to provide branched S-allyl carbamothioates in high yield and high enantiomeric purity.
钯 (II) 络合物 [(Rp,S)-COP-Cl]2 及其对映异构体在温和条件下催化线性前手性 O-烯丙基硫代氨基甲酸酯的重排,以高产率和高对映体纯度提供支链 S-烯丙基硫代氨基甲酸酯。
Stereoselective Synthesis of Pamamycin-607
作者:Jeong、Eun Joo Kang、Lee Taek Sung、Sung Kil Hong、Eun Lee
DOI:10.1021/ja0279646
日期:2002.12.1
A macrodiolide antibiotic pamamycin-607 was synthesized by joining two hydroxy acid components. Three cis-2, 5-disubstituted tetrahydrofuran rings in the molecule were stereoselectively prepared by radical cyclization reactions of beta-alkoxyvinyl ketone intermediates and a beta-alkoxymethacrylate substrate. The key step of the synthesis is characterized by the predominant threo product formation in
pentafluorophenyltrimethylsilane (I) and cyanomethyltrimethylsilane (II) with enolizable ketones in the presence of a catalytic amount of potassium cyanide-18-crown-6 complex gave the corresponding trimethylsilyl enolethers. The same dehydrogenative silylation of acetylacetone and benzoylacetone with silane I was extended to the preparation of 2,4-bis(trimethylsiloxy)-1,3-pentadiene and 1-phenyl-1,3 -bis(trimethylsiloxy)-1
在催化量的氰化钾-18-冠-6配合物存在下,用可烯丙基化的酮处理五氟苯基三甲基硅烷(I)和氰基甲基三甲基硅烷(II),得到相应的三甲基甲硅烷基烯醇醚。乙酰丙酮和苯甲酰基丙酮与硅烷I的相同脱氢甲硅烷基化反应扩展到了2,4-双(三甲基甲硅烷氧基)-1,3-戊二烯和1-苯基-1,3-双(三甲基甲硅烷氧基)-1,3-丁二烯的制备, 分别。在相同条件下用二甲基双(五氟苯基)硅烷对乙酰丙酮和苯甲酰基丙酮进行脱氢甲硅烷基化反应,得到了新颖的杂环基5-亚甲基-2,6-二氧杂-1-硅酰基己烯-3-烯。在研究的反应中,硅烷的甲硅烷基化能力按Me 3 SiCN⋍Me 2 Si(CN)2的顺序增加<Me 3 SiCH 2 CN <Me 3 SiC 6 F 5> Me 2 Si(C 6 F 5)2。另一方面,氰化钾-18-冠-6配合物催化将硅烷I或II加成至不可烯化的化合物如苯甲醛,巴豆醛和甲基(三乙基锗基)乙烯酮的羰基上。
Substoichiometric TiCl4-mediated vicinal difunctionalization of α,β-acetylenic ketones for the synthesis of β-halo Baylis–Hillman olefins
作者:Han-Xun Wei、Ju J Gao、Guigen Li
DOI:10.1016/s0040-4039(01)02020-2
日期:2001.12
α-hydroxyalkylation/β-chlorination of α,β-acetylenicketones in the presence of (n-Bu)4NI. This method provides the concise synthesis of (E)-β-halo Baylis–Hillman adducts. No β-iodo products were detected when using this combination of halogen sources. The reaction process involves 1,4-addition of chloro anion released from TiCl4 onto α,β-acetylenicketones to give TiCl3–allenolate intermediates followed
发现在(n -Bu)4 NI存在下,亚化学计量的四氯化钛有效地促进和参与了α,β-炔酮的串联α-羟烷基化/β-氯化反应。此方法提供了(E)-β-卤代Baylis-Hillman加合物的简明合成。当使用这种卤素源组合时,没有检测到β-碘产物。反应过程涉及将TiCl 4释放的氯阴离子1,4-加成到α,β-炔基酮上,得到TiCl 3-烯丙基化物中间体,然后由路易斯酸钛促进的羰基加成反应。中等至良品率(53–77%)和出色的E / Z 对于10个实例,已经获得了立体选择性(> 95%)。
Mutation of Cysteine-295 to Alanine in Secondary Alcohol Dehydrogenase from Thermoanaerobacter ethanolicus Affects the Enantioselectivity and Substrate Specificity of Ketone Reductions
作者:Christian Heiss、Maris Laivenieks、J.Gregory Zeikus、Robert S Phillips
DOI:10.1016/s0968-0896(01)00073-6
日期:2001.7
The mutation of Cys-295 to alanine in Thermoanaerobacter ethanolicus secondaryalcoholdehydrogenase (SADH) was performed to give C295A SADH, on the basis of molecular modeling studies utilizing the X-ray crystal structure coordinates of the highly homologous T. brockii secondaryalcoholdehydrogenase (1YKF.PDB). This mutant SADH has activity for 2-propanol comparable to wild-type SADH. However, the