作者:Edward Danielyan、Maayan Zuniga、Khoi Hoang、David H. Magers、Daniel A. Osborne、Edward J. Valente
DOI:10.1007/s10870-023-00984-2
日期:2023.12
the coumarin carboxy oxygen, apparently favors rotamers that bring the side-chain ketone into proximity with the coumarin enolic hydroxy. The less-polar by-product of the Michael addition has been characterized by spectroscopy and crystallography as 2,2,4-trimethyl[2H,5H]pyrano[3,2-c][1]benzopyran-5-one. Computations on the alkyl warfarin analog 2-hydroxy-2,4-dimethyl-3,4-dihydro-2H,5H-pyrano[3,2-c]
4-羟基香豆素与异丙叉丙酮(华法林的类似物)迈克尔加成的极性更强的产物,结晶为外消旋环状香豆素半缩酮 2-羟基-2,4,4-三甲基-3,4-二氢-2 H ,5 H-吡喃并[3,2-c][1]苯并吡喃-5-酮。晶体出现在单斜晶系,空间群P 2(1)/ n,a 6.6655(4)Å,b 12.9450(7)Å,c 14.5809(7)Å,β 97.909(5)°,Z = 4。在核磁共振(400 MHz)溶液中,对映体香豆素半缩酮之间通过未观察到的中间开放互变异构体存在动态平衡。非对映体亚甲基和甲基 H 在非极性溶剂(乙酸和氯仿)中交换缓慢,在极性非质子溶剂(丙酮和二甲亚砜)中交换速度要快得多。在甲醇中,动态行为在 288-310 K 的慢交换区域开始,在 310.5 K 处信号聚结,然后是快速交换行为。发现环-开-环(外消旋化)的障碍为 ΔG ‡ = + 63(1) kJ/mol(在 CD 3