One-pot sequential cross-metathesis/hydride reduction: highly stereoselective synthesis of primary (E)-allylic alcohols from terminal olefins
作者:Tapas Paul、Gopal Sirasani、Rodrigo B. Andrade
DOI:10.1016/j.tetlet.2008.03.132
日期:2008.5
Several di- and trisubstituted primary (E)-allylic alcohols have been prepared from the corresponding terminal olefins in a highly stereoselective manner (>20:1 E/Z) by sequencing olefin cross-metathesis (CM) with hydride reduction (DIBAL-H) in good yields utilizing only commercially available reagents in a one-pot fashion. The method is a reliable alternative to the direct CM of terminal olefins with
通过以氢化物还原法对烯烃交叉复分解(CM)进行测序(DIBAL-H),从相应的末端烯烃以高度立体选择性的方式(> 20:1 E / Z)制备了几种二和三取代的伯(E)烯丙基醇。)仅使用一锅法仅使用市售试剂即可获得高收率)。该方法是端烯与烯丙醇直接CM的可靠替代方法,后者并不总是立体选择性的,而是高度依赖底物的。
Identification of a Thioesterase Bottleneck in the Pikromycin Pathway through Full-Module Processing of Unnatural Pentaketides
作者:Douglas A. Hansen、Aaron A. Koch、David H. Sherman
DOI:10.1021/jacs.7b06432
日期:2017.9.27
Polyketide biosynthetic pathways have been engineered to generate natural product analogs for over two decades. However, manipulation of modular typeIpolyketidesynthases (PKSs) to make unnatural metabolites commonly results in attenuated yields or entirely inactive pathways, and the mechanistic basis for compromised production is rarely elucidated since rate-limiting or inactive domain(s) remain
二十多年来,聚酮化合物生物合成途径已被设计为生成天然产物类似物。然而,操纵模块化 I 型聚酮化合物合酶 (PKS) 以制造非天然代谢物通常会导致产量减弱或完全失活,并且由于限速或失活域仍未确定,因此很少阐明影响生产的机制基础。因此,我们合成并分析了一系列模拟早期通路工程的修饰 pikromycin (Pik) pentaketides,以在体外探测 PikAIII-TE 模块的底物耐受性。截短的五肽以不同的效率加工成相应的大环内酯,而具有差向异构化手性中心的五肽被 PikAIII-TE 加工不良,无法生成 12 元环产物。扩展但过早卸载的分流产物的分离和鉴定表明,Pik 硫酯酶 (TE) 域具有有限的底物灵活性,并在非天然底物的加工中起到看门人的作用。具有差向异构化亲核羟基的类似六酮化合物的合成允许直接评估切除的 TE 结构域的底物立体选择性。差向异构化的六酮化合物没有进行环化,而是完全水解,证实了
Sequencing cross-metathesis and non-metathesis reactions to rapidly access building blocks for synthesis
作者:Gopal Sirasani、Tapas Paul、Rodrigo B. Andrade
DOI:10.1016/j.tet.2011.01.080
日期:2011.3
The olefin cross-metathesis reaction has been sequenced with four common organic transformations in a one- or two-pot manner to rapidly access useful building blocks. Those reactions are: (1) phosphorus-based olefination (e.g.. Wittig and Horner-Wadsworth-Emmons); (2) hydride reduction; (3) Evans propionate aldol reaction; (4) Brown allyl- and Roush crotyl-boration. The products of these reactions include stereodefined 2,4-dienoates, trans allylic alcohols, syn-propionate aldols, and chiral non-racemic homoallylic alcohols, respectively. Many of these intermediates have been carried further to natural products, demonstrating the utility of the methodology. (C) 2011 Elsevier Ltd. All rights reserved.
Aldol methodology: synthesis of versatile intermediates, 3-hydroxy-2-vinylcarbonyl compounds