Electrophilic additions to dienes and the 1-phenylpropenes with pyridine-halogen complexes and tribromides. Effects on stereochemistry and product ratios
Two Syntheses of (−)-Kainic Acid via Highly Stereoselective Zinc-ene Cyclizations
作者:Justin M. Chalker、Ao Yang、Kai Deng、Theodore Cohen
DOI:10.1021/ol701733u
日期:2007.9.1
Two concise, high-yielding syntheses of enantioenriched (-)-kainic acid are presented. Both routes feature a Pd-catalyzed Zn-ene cyclization that proceeds with complete diastereoselectivity. The key step can be carried out on a multigram scale, and the overall yields are among the highest to date for this marine alkaloid.
Role of Ring <i>Ortho</i> Substituents on the Configuration of Carotenoid Polyene Chains
作者:Minsoo Kim、Hyunuk Jung、Albert C. Aragonès、Ismael Díez-Pérez、Kwang-Hyun Ahn、Wook-Jin Chung、Dahye Kim、Sangho Koo
DOI:10.1021/acs.orglett.7b03930
日期:2018.1.19
The 9-(Z)-configuration was exclusively obtained in the carotenoid polyenechain irrespective of olefination and disconnection methods for terminal ortho-unsubstituted benzene rings. The 2,6-dimethyl substituents in the terminal rings secure an all-(E)-polyene structure. The single molecular conductance of the pure 9-(Z)-carotene was measured for the first time to be 1.53 × 10–4 ± 6.37 × 10–5G0, whose
9-(Z)-构型仅在类胡萝卜素多烯链中获得,而与末端邻-未取代的苯环的烯烃化和断开方法无关。末端环中的2,6-二甲基取代基可确保全(E)-多烯结构。首次测得纯9-(Z)-胡萝卜素的单分子电导为1.53×10 –4 ±6.37×10 –5 G 0,其值为全(E)-的47%胡萝卜素((3.23×10 -4)±(1.23×10 -4)G 0)。
General and systematic synthetic entry to carotenoid natural products