Vinylogous Mannich Reactions. The Asymmetric Total Synthesis of (+)-Croomine

摘要

The alkaloid-rich extracts obtained from plants belonging to the Stemonaceae family (Stemona and Croomia species) have been used in traditional Chinese folk medicine to prepare herbal teas for treating numerous disorders, including pertussis, pulmonary tuberculosis, and bronchitis; several alkaloids also exhibit insecticidal activity. Although this class of alkaloids is relatively small, there is an increasing interest in representative members of the family owing to their unique and complex structures coupled with the rich opportunities for developing new chemistry for their synthesis. As illustrated by the prototypical examples croomine (1) and stemonine (2), these novel polycyclic alkaloids incorporate a butyrolactone ring that is appended or annelated to a 1-azabicyclo[5.3.0]decane nucleus.