Biomimetic Synthesis of (.+-.)-Galanthamine and Asymmetric Synthesis of (-)-Galanthamine Using Remote Asymmetric Induction
作者:Manabu Node、Sumiaki Kodama、Yoshio Hamashima、Takahiro Katoh、Kiyoharu Nishide、Tetsuya Kajimoto
DOI:10.1248/cpb.54.1662
日期:——
employing a novel remote asymmetric induction, where conformation of the seven-membered ring in the product of the phenol coupling was restricted by forming a fused-chiral imidazolidinone ring with D-phenylalanine on the benzylic C-N bond of the tri-O-alkylated gallyl amino moiety. The conformational restriction and successive debenzylation of the protected hydroxyl groups on the pyrogallol ring caused
(+/-)-加兰他敏(1)通过应用PIFA介导的N-(4-羟基)苯乙基-N-(3',4',5'-三烷氧基)苄基甲酰胺( 15b)作为关键步骤。由于底物(15b)中邻苯三酚部分的对称特性,苯酚偶合产生唯一的偶合产物,除了氧化剂的挥发性成分。根据上述策略的成功结果,采用新颖的远程不对称诱导合成(-)-加兰他敏(1),其中苯酚偶联产物中的七元环构象通过形成在三-O-烷基化的胆酰基氨基部分的苄基CN键上具有D-苯丙氨酸的稠合手性咪唑啉酮环。