Intramolecular Chiral Relay at Stereogenic Nitrogen. Synthesis and Application of a New Chiral Auxiliary Derived from (1<i>R</i>,2<i>S</i>)-Norephedrine and Acetone
作者:Shawn R. Hitchcock、David M. Casper、Jeremy F. Vaughn、Jennifer M. Finefield、Gregory M. Ferrence、Joel M. Esken
DOI:10.1021/jo035325n
日期:2004.2.1
aldol addition reaction by treatment with titanium tetrachloride, triethylamine, and a variety of aldehydes at 0 °C. The aldol adducts 10a−i and 11a,b were found to have diastereoselectivities ranging from 8:1 to >99:1 favoring the formation of the non-Evans syn configuration. The absolute stereochemistry of the adduct 10a was determined by acid hydrolysis. This process afforded the N4-isopropyloxadiazinone
(1 - [R,2小号) -降麻黄碱已经以一种新颖的3,4,5,6-四氢-2的合成已经采用ħ -1,3,4-恶二嗪-2-酮通过还原性烷基化,用丙酮,Ñ -亚硝化,还原和环化。用丙二酰氯或3-硫代苯丙酰氯处理恶二嗪酮,分别得到相应的N 3-酰化的恶二嗪酮9a和9b。N 3-硫代苯丙酰基羰基恶二嗪酮9b的X射线晶体分析表明,C 2-尿烷羰基和N 3-羰基以反平面构象排列。通过在0℃下用四氯化钛,三乙胺和各种醛处理,将恶二嗪酮应用于钛介导的不对称羟醛加成反应中。发现醛醇加合物10a - i和11a,b具有8∶1至> 99∶1的非对映选择性,有利于形成非伊文斯同构型。通过酸水解确定加合物10a的绝对立体化学。该过程提供了N 4-异丙基恶二嗪酮8和(2 S,3 S对映体过量≥95%的)-3-羟基-2-甲基-3-苯基丙酸14