Application of furanyl carbamate cycloadditions toward the synthesis of hexahydroindolinone alkaloids.
Application of furanyl carbamate cycloadditions toward the synthesis of hexahydroindolinone alkaloids.
复制标题
呋喃基氨基甲酸酯环加成在六氢二氢吲哚酮生物碱合成中的应用。
DOI：
10.1021/jo010020z
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Wu,T
中科院分区：
文献类型：
--
作者：
Padwa,A;Brodney,MA;Dimitroff,M;Liu,B;Wu,T
通过带有链烯基的呋喃基氨基甲酸酯的分子内Diels−桤木环加成反应（IMDIA），可以方便地合成各种取代的六氢吲哚啉酮。最初形成的[4 + 2]-环加合物经历氮辅助开环，然后将所得的两性酮去质子化，得到重排的酮。的立体化学结果IMMOR环加成具有侧臂的拴链烯基基团取向的syn相对于氧桥。利用该方法完成了（±）-中膜和（±）-卷柏烷的合成路线。有可能对最初形成的六氢吲哚啉酮环进行立体选择性还原以产生顺-3a-芳基-氢吲哚骨架。利用[4 + 2]-环加成/重排反应合成了中国观赏兰（±）-石斛碱。通过N-[（2-甲基-2-环戊烯基）甲基]-N-（4-异丙基-呋喃-2-基）氨基甲酸叔丁酯的合成，立体选择性地形成了三环生物碱核。Kende的高级中间体33通过标准转化在另外七个步骤中制备，从而完成（±）-石斛碱的正式合成。
A convenient synthesis of various substituted hexahydroindolinones has been achieved by an intramolecular Diels−Alder cycloaddition reaction (IMDAF) of furanyl carbamates bearing tethered alkenyl groups. The initially formed [4 + 2]-cycloadduct undergoes nitrogen-assisted ring opening followed by deprotonation of the resulting zwitterion to give the rearranged ketone. The stereochemical outcome of the IMDAF cycloaddition has the sidearm of the tethered alkenyl group oriented syn with respect to the oxygen bridge. A synthetic route to (±)-mesembrane and (±)-crinane was accomplished using this methodology. It was possible to carry out a stereoselective reduction of the initially formed hexahydroindolinone ring to produce thecis-3a-aryl-hydroindole skeleton. A related [4 + 2]-cycloaddition/rearrangement sequence was also used for a formal synthesis of the Chinese ornamental orchid (±)-dendrobine. The tricyclic alkaloid core was formed stereoselectivity from the thermolysis ofN-[(2-methyl-2-cyclopentenyl)methyl]-N-(4-isopropyl-furan-2-yl)carbamic acidtert-butyl ester. Kende's advanced intermediate33was prepared in seven additional steps by standard transformations, thereby completing a formal synthesis of (±)-dendrobine.