抗霉素是众所周知的由链霉菌产生的抗真菌代谢物之一。新抗霉素及其类似物,即具有 15 元四酯环的扩环抗霉素,已被证明是致癌蛋白 GRP78/BiP 和 K-Ras 的有效调节剂。异新霉素是从Streptomyces fradiae中分离出来的IFO12773 (ISP 5063) 作为新抗霉素发酵过程中的次要代谢物,是第一个报道的不含大环内酯核心的抗霉素家族抗生素。在这项研究中,我们探索了异抗霉素的全合成和立体化学分配,作为对新抗霉素进行结构-活性研究的一种方法。考虑到新抗霉素的生物合成途径,我们推测异抗霉素的立体化学与新抗霉素的立体化学相同。我们的目标分子与 (1 S ,2 R ,5 S ,6 S ,14 R ,15 R ,17 S) 配置是通过使用手性池构建块实现的。合成样品和天然样品的光谱数据比较证实了我们对天然异抗霉素立体化学的假设。
Nickel-Catalyzed Asymmetric Kumada Cross-Coupling of Symmetric Cyclic Sulfates
作者:Meredith S. Eno、Alexander Lu、James P. Morken
DOI:10.1021/jacs.6b03384
日期:2016.6.29
Nickel-catalyzed enantioselective cross-couplings between symmetric cyclic sulfates and aromatic Grignard reagents are described. These reactions are effective with a broad range of substituted cyclic sulfates and deliver products with asymmetric tertiary carbon centers. Mechanistic experiments point to a stereoinvertive SN2-like oxidative addition of a nickel complex to the electrophilic substrate
Enantioselective synthesis of 2-benzyloxy alcohols and 1,2-diols via alkylation of chiral glycolate imides. A convenient approach to optically active glycerol derivatives
The alkylation of the chiral enolates of glycolate imides 2a and 2b proceedes in highly diastereoselective manner to give 2'-substituted products in good yield. Reductive cleavage with LiBH4 affords the corresponding 2-benzyloxyalcohols 3a-c and 11a-b which are successively converted to 1,2-diols in high optical purity. By this method (R)-1-propanoyloxy-2, 3-propanediol 9 and (S)-1-tridecyloxy-2,3-propanediol
Using a trifluoromethylated oxazolidine (Fox) chiral auxiliary, the hydroxylation reaction of enolates was very efficiently performed under smooth and friendly conditions with molecular oxygen as oxidizer. This reaction occurred with an extremely high diastereoselectivity. After cleavage, the chiral auxiliary is efficiently recovered and highly valuable enantiopure oxygenated carboxylic acids and alcohols