Synthesis of Tetrahydroisoquinoline Alkaloids and Related Compounds through the Alkylation of Anodically Prepared α-Amino Nitriles
作者:Lotfi Benmekhbi、Fadila Louafi、Thierry Roisnel、Jean-Pierre Hurvois
DOI:10.1021/acs.joc.6b01419
日期:2016.8.5
α-Amino nitrile 2a was conveniently prepared in two individual steps from chiral hexafluorophosphate salt isoquinolinium (−)-8b including anodic cyanation as an efficient means to activate the sp3 C1–H bond of the THIQ nucleus. The lithiation of 2a was carried out in THF at −80 °C in the presence of LDA to produce a stable α-amino carbanion which was condensed on a large variety of alkyl halides. The
α-氨基腈2a可以方便地在两个独立的步骤中从手性六氟磷酸盐异喹啉鎓(-)- 8b制备,包括阳极氰化作为激活THIQ核的sp 3 C1-H键的有效方法。2a的锂化反应是在LDA的存在下于-80°C的THF中于-80°C进行的,以生成稳定的α-氨基碳负离子,将其冷凝在多种烷基卤上。在作为氢化物供体的NaBH 4存在下,在乙醇中对所得的季α-氨基腈进行立体选择性还原脱氰反应,生成N -Boc-1-烷基-THIQs(+)- 10a – g除去手性辅助基团后最多可达到97:3 er。对THIQ(+)- 1f的ORTEP视图的检查表明,新创建的立体生成中心具有绝对的S构型。同样地,在四个后处理步骤中,从α-氨基腈(+)- 2b以63%的总收率合成了(-)-xylopinine 。在此过程中,将对映浓缩的(-)-去甲月桂花碱与1当量的(-)- N-乙酰基-1-亮氨酸的混合物(90:10)结晶,得到亮氨酸盐(+)-