Total synthesis of malyngamide X and its 7′S-epi isomer
摘要:
Stereoselective syntheses of malyngamide X (1) and its 7'(S)-epimer are described. A Lewis acid (Et2AlCl) mediated anti-aldol reaction was employed to generate the stereocenters C-7 and C-8. The route is convergent and provides a convenient access to the synthesis of structural variants of malyngamide X. Stereochemistry at C-7' in the molecules of natural and synthetic 1, and 7'(S)-epi 1 was confirmed by NMR chiral solvation experiments. (c) 2007 Elsevier Ltd. All rights reserved.
The first totalsynthesis of (+)-cytosporolide A was achieved by a biomimetic hetero-Diels-Alder reaction of (-)-fuscoatrol A with o-quinone methide generated from (+)-CJ-12,373. The dienophile, highly oxygenated caryophyllene sesquiterpenoid (-)-fuscoatrol A, was synthesized from the synthetic intermediate in our previous totalsynthesis of (+)-pestalotiopsin A. The o-quinone methide precursor, isochroman
(+)-胞孢内酯 A 的首次全合成是通过 (-)-fuscoatrol A 与 (+)-CJ-12,373 产生的邻醌甲基化物的仿生异狄尔斯-阿尔德反应实现的。亲二烯体,高度氧化的石竹烯倍半萜 (-)-fuscoatrol A,是从我们之前 (+)-pestalotiopsin A 全合成中的合成中间体合成的。 邻醌甲基化物前体,异色满甲酸 (+)-CJ-12,373 , 是通过 Kolbe-Schmitt 反应和 oxa-Pictet-Spengler 反应合成的。这两种化合物的杂狄尔斯-阿尔德反应具有完全的化学选择性、区域选择性和立体选择性,以产生复杂的胞孢内酯骨架的五环系统。这种全合成明确表明天然胞孢内酯 A 具有先前建议的结构。
[3,3]-Acyloxy Rearrangement-Triggered Regioselective Hydration of δ-Acetoxy-α,β-Alkynoates/Halo Alkynes
作者:Kishor L. Mendhekar、Tapas R. Pradhan、Debendra K. Mohapatra
DOI:10.1021/acs.joc.0c00061
日期:2020.4.3
that is facilitated by an unusual interception of an electrophilic intermediate by water generated via acetate group participation during [3,3]-acyloxy rearrangement. Various carboxylate-directing groups including acetate, acrylates, pivalates, benzoate or its derivatives, and those derivedfrom bioactive natural products were successfully implemented to direct the regioselective hydration for various
Asymmetric synthesis of 3-substituted 3,4-dihydroisocoumarins via stereoselective addition of laterally lithiated chiral 2-(o-tolyl)oxazolines to aldehydes followed by diastereomer-selective lactonization
作者:Yuji Kurosaki、Tsutomu Fukuda、Masatomo Iwao
DOI:10.1016/j.tet.2005.01.103
日期:2005.3
Lateral lithiation of (S)-4-isopropyl-2-(o-tolyl)oxazoline in diethyl ether followed by the reaction with aldehydes in the presence of TMEDA produced the addition products with stereoselectivities up to 84% de. Utilization of TMEDA as a ligand is essential for the good selectivity. Rationale for the stereoselectivity is proposed based on ab initio calculation of the lateral lithio species. The major
Synthesis and Absolute Configuration of Two Natural Phenolic Homobenzyl Esters
作者:Murong Xu、Shijun Zhu、Zejun Xu、Yikang Wu、Po Gao
DOI:10.1002/cjoc.201500315
日期:2015.7
natural phenolic homobenzyl esters, isolated from Phragmipedium calurum (an orchid) and Eupatorium fortunei TURCZ (a perennial herb in the Asteraceae family), respectively, were synthesized in enantiopure forms. By comparison of the optical rotations for the synthetic and the natural samples, the absoluteconfigurations for the natural products were reliably assigned. The synthesis also enables establishment
On the proposed structures and stereocontrolled synthesis of the cephalosporolides
作者:Sami F Tlais、Gregory B Dudley
DOI:10.3762/bjoc.8.146
日期:——
The synthesis of four candidate stereoisomers of cephalosporolide H is described, made possible by a zinc-chelation strategy for controlling the stereochemistry of oxygenated 5,5-spiroketals. The same strategy likewise enables the first stereocontrolledsynthesis of cephalosporolide E, which is typically isolated and prepared admixed with its spiroketal epimer, cephalosporolide F.
描述了头孢菌素 H 的四种候选立体异构体的合成,通过锌螯合策略控制氧化 5,5-spiroketals 的立体化学成为可能。同样的策略同样使头孢菌素 E 的首次立体控制合成成为可能,它通常是分离出来的,并与其螺缩酮差向异构体头孢菌素 F 混合制备。