Pictet-Spengler Cyclizationvs. Aminal Formation: Competing Reaction Pathways of Benzo[b][1,7]naphthyridines Controlled by the Configuration
摘要:
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.
Pictet-Spengler Cyclizationvs. Aminal Formation: Competing Reaction Pathways of Benzo[b][1,7]naphthyridines Controlled by the Configuration
摘要:
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.
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.