regioselective synthetic pathway is reported to prepare 5-hydroxytetrahydroprotoberberines, starting from readily available isoquinoline derivatives. Bromoacetaldehyde diethyl acetal is found to be an effective and convenient reagent for N-alkylation of the latter derivatives, and subsequent acidic cyclization afforded the corresponding tetracyclic berbines in excellent overall yield. Stereochemical assignments
据报道,从容易获得的
异喹啉衍
生物开始,区域选择性合成途径可制备5-羟基四氢小ber碱。发现
溴乙醛二
乙缩醛是用于后者衍
生物的N-烷基化的有效和方便的试剂,并且随后的酸性环化以优异的总收率提供了相应的四环berbines。立体
化学分配是基于1 H NMR数据进行的,这些数据受去耦实验和NOE差异测量的支持。