Synthetic approaches to pentacyclic triterpenes of the arborane family II1 - @Tetracyclic intermediates
摘要:
Diels-Alder condensation of the bicyclic diene 1 with 2,6-dimethylbenzoquinone 2 under thermal and Lewis acid-catalyzed conditions gives the diastereomers 3, 4, 5 and 8; their structures are demonstrated by NMR analysis, in full agreement with the conformations deduced from molecular mechanics.