Asymmetric Synthesis of 4-Deoxyverrucarol via Two Types of Ring Expansion Reactions
作者:Junji Miyata、Hideo Nemoto、Masataka Ihara
DOI:10.1021/jo991430e
日期:2000.1.1
Asymmetric synthesis of a trichothecane analogue, 4-deoxyverrucarol (2), was carried out through two types of ring expansion reactions. First, synthesis of the racemate of 2 was investigated. Thus, 1-[1-(tert-butyldimethylsiloxy)-ethyl]-1-methoxycarbonyl-2-hexen-4-on e (10), prepared by Diels-Alder reaction, was converted into the cyclopropylidene 15. The cyclobutanone (+/-)-18 was obtained from 15
通过两种类型的扩环反应进行了三氯噻烷类似物4-脱氧维鲁卡罗(2)的不对称合成。首先,研究了2的外消旋体的合成。因此,通过Diels-Alder反应制备的1- [1-(1-叔丁基二甲基甲硅烷氧基)-乙基] -1-甲氧基羰基-2-己烯-4-酮(10)被转化为环亚丙基15。环丁酮(+从15通过二羟基化获得/-)-18,然后在咪唑和Florisil存在下用SO(2)Cl(2)进行连续处理。将(+/-)-18转变为乙烯基环丁醇(+/-)-19后,用Pd(OAc)(2)进行第二次扩环反应,得到环戊酮(+/-)-20。产物通过环己烯酮(+/-)-22转化为4-deoxyverrucarol(2)的外消旋体,但是引入双键期间的非对映选择性不令人满意。在不对称合成的情况下提高了选择性。通过15与73%ee的AD反应制备旋光性环丁酮(+)-18。通过钯介导的扩环反应将(+)-18转化为环己酮(-)-30后,使