Synthesis of (−)-Sedinine by Allene Cyclization and Iminium Ion Chemistry Roderick W. Bates Yongna Lu 10.1021/ol1016492.s001 https://acs.figshare.com/articles/journal_contribution/Synthesis_of_Sedinine_by_Allene_Cyclization_and_Iminium_Ion_Chemistry/2735935 A synthesis of the <i>sedum</i> alkaloid sedinine has been achieved employing silver(I)-catalyzed allenic hydroxylamine cyclization and ring-closing metathesis to form a bicyclic <i>N</i>,<i>O</i>-acetal. Ring opening of this acetal with a silyl enol ether under Lewis acidic conditions is exclusively <i>trans</i> selective, leading to the natural product after reduction. On the other hand, conversion of the bicyclic <i>N</i>,<i>O</i>-acetal to a semicyclic <i>N</i>,<i>O</i>-acetal results in no stereoselectivity during such a reaction. The contrasting results can be rationalized by consideration of the conformation of the iminium ions. 2010-09-03 00:00:00 Allene Cyclization semicyclic bicyclic cyclization iminium ions metathesi hydroxylamine allenic silyl enol ether consideration conformation Sedinine acetal synthesis opening conversion Lewis acidic conditions stereoselectivity Iminium Ion Chemistry tran sedum alkaloid sedinine Synthesi