螺环素 A、C 和 D 是已在海洋真菌菌株 LL-37H248 中鉴定的代谢物。它们独特的多环结构和有趣的生物活性使它们成为合成社区的有吸引力的目标。基于 5-取代萘醌的可扩展对映选择性环氧化、氧化/螺酮缩酮级联、苯酚单元的邻位选择性氯化和肟酯导向的乙酰氧基化、(-)-螺环素 A 和 C 的对映选择性全合成以及已经实现了 (-)-spiroxin D 的首次全合成。
Development of C-6′-modified quinine-derived phase-transfer catalysts and their application in the enantioselective α-hydroxylation of β-dicarbonyl compounds
We have developed C-6'-modified quinine quaternary ammonium salts as phase transfer catalysts for alpha-hydroxylation of beta-dicarbonyl compounds. The quinine quaternary ammonium salts, which was modified at C-6' and the N atom, had good activity for alpha-hydroxylation of B-dicarbonyl compounds. By using 5 mol % of 6-hydroxyl-N-(4'-fluoro-2'-trifluoromethyl)quinine quaternary ammonium salt as the organocatalyst, cumene hydroperoxide as the oxidant, toluene as the solvent, and 50% K2HPO4 as the aqueous alkali at room, temperature, the yield and enantioselectivity of the alpha-hydroxylation of beta-keto esters were 95% and 88%, respectively. This catalytic system was also applicable for beta-keto amides (92% yield and 76% ee). (C) 2016 Elsevier Ltd. All rights reserved.