Abstract
Excerpt: The asymmetric addition of metalated [ (methylenedioxy) isoquinolyl] oxazolines is 100% selective for the erythro(a-hydroxybenzyl)isoquinoline diastereomers, with 2:1 selectivity of the two possible erythro stereoisomers.Enrichment to 100% ee after removal of the auxiliary and conversion to (-)-bicuculline and (+)-bicuculline diolestablish the absolute configuration of the major addition product. Inversion of the C-9 hydroxyl affords entryinto the threo series as well. The asymmetric carbonyl addition was used to synthesize, for the first time, thephthalide-isoquinoline hemiacetals corytensine and egenine, confirming the previously assigned structures andabsolute configurations, and establishing the identity of egenine with decumbensine and of corytensine withepi-a-decumbensine.