Enantioselective Total Syntheses of theIpecacuanha Alkaloid Emetine, theAlangium Alkaloid Tubulosine and a Novel Benzoquinolizidine Alkaloid by Using a Domino Process
作者:Lutz F. Tietze、Nils Rackelmann、I. Müller
DOI:10.1002/chem.200306039
日期:2004.6.7
The first enantioselective syntheses of the Ipecacuanha alkaloid emetine (1) and the Alangium alkaloid tubulosine (2) is described employing a domino Knoevenagel/hetero-Diels-Alder reaction and an enantioselective catalytic transfer hydrogenation of imines as key steps. Thus, hydrogenation of the imine 15 with the catalyst (R,R)-16 gives the tetrahydroisoquinoline 14 with 95 % ee which was transformed
Ipecacuanha生物碱metetine(1)和Alangium alkaloidtubulosine(2)的第一个对映选择性合成描述了采用多米诺Knoevenagel / hetero-Diels-Alder反应和亚胺的对映选择性催化转移氢化作为关键步骤。因此,用催化剂(R,R)-16氢化亚胺15得到具有95%ee的四氢异喹啉14,其被转化为醛(1S)-7。(1S)-7与6和8的三组分多米诺反应导致19,在第二个多米诺过程中,先用K(2)CO(3)在甲醇中处理,然后氢化得到苯并喹啉4非对映体22和23,总产率为66%。用胺3和5进一步转化4分别得到对映纯的Emetine(1)和tubulosine(2)。此外,从19开始,合成了新的苯并喹喔啉生物碱34。该化合物类似于缬草胺胆碱生物碱二氢黄嘌呤31,该化合物迄今尚未分离出来,但很可能在自然界中也存在。