The first total synthesis of oxazolomycin A, a structurally novel oxazole polyene gamma-lactam/beta-lactone antibiotic, is described. Key features Include the stereocontrolled construction of the right-hand heterocyclic core by taking advantage of an In(III)-catalyzed Conia-ene type cyclization and the asymmetric synthesis of the left-hand segment starting with a Cinchona alkaloid-catalyzed cyclocondensation of an aldehyde with an acid chloride.
The first total synthesis of oxazolomycin A, a structurally novel oxazole polyene gamma-lactam/beta-lactone antibiotic, is described. Key features Include the stereocontrolled construction of the right-hand heterocyclic core by taking advantage of an In(III)-catalyzed Conia-ene type cyclization and the asymmetric synthesis of the left-hand segment starting with a Cinchona alkaloid-catalyzed cyclocondensation of an aldehyde with an acid chloride.
An effective method for the protection of carboxylic acids with a triisopropylsiloxymethyl (TIPSOCH2) group is described. The reactions of various carboxylic acids with C12H25SCH2OTIPS in the presence of CuBr2, Et3N, and molecular sieves 4A afford the corresponding triisopropylsiloxymethyl esters in good yields.
The proposed structure of mohangic acid C (3) was stereoselectively synthesized via a catalytic asymmetric aldol reaction to install a p-aminoacetophenone moiety, Marshall propargylation furnishing two stereocenters, and Cu-mediated Stille-type coupling to construct the whole framework of 3.
通过催化不对称醛醇反应安装对氨基苯乙酮部分、提供两个立体中心的 Marshall 炔丙基化和 Cu 介导的 Stille 型偶联构建 3 的整个框架,立体选择性合成了所提出的 mohangic 酸 C ( 3 ) 结构。
Stereoselective synthesis of the right-hand cores of 16-methylated oxazolomycins
作者:Kohei Eto、Jun Ishihara、Susumi Hatakeyama
DOI:10.1016/j.tet.2017.12.036
日期:2018.2
The right-hand heterocyclic cores of oxazolomycins having either 16R or 16S-methyl group configurations on the beta-lactones were stereoselectively synthesized from the common intermediate utilized for our previous syntheses of neooxazolomycin and oxazolomycin A. In addition, the right-hand segment required for the synthesis of KSM-2690 and lajollamycin members was also synthesized in a stereo-selective manner. (C) 2017 Elsevier Ltd. All rights reserved.