Pictet-Spengler Cyclizationvs. Aminal Formation: Competing Reaction Pathways of Benzo[b][1,7]naphthyridines Controlled by the Configuration
作者:Tim Dickner、Sabine Laschat
DOI:10.1002/1522-2675(20010711)84:7<2064::aid-hlca2064>3.0.co;2-y
日期:2001.7.11
Diastereoisomeric benzo[b][1,7]naphthyridines 13a,b were synthesized in nine steps from L-DOPA employing a Lewis acid-catalyzed cyclization of N-(4-methylpent-3-enyl)-alpha -amino aldehydes as the key step. Under aprotic Pictet-Spengler conditions, compounds 13a,b undergo different reaction pathways depending on the relative configuration. Whereas trans,cis-diastereoisomer 13a yielded the desired Pictet-Spengler cyclization product albeit in very low yield, the corresponding concave-shaped all-cis-diastereoisomer 13b undergoes intramolecular aminal formation.