THE KETENE THIOACETAL GROUP AS A CATIONIC CYCLIZATION TERMINATOR. A SYNTHESIS OF THE PYRROLIZIDINE RING SYSTEM.

Article abstract of DOI:10.1016/S0040-4039(00)87412-2

A cationic cyclization to the pyrrolizidine ring system is reported in which a ketene thioacetal group serves as an efficient terminator for 5-membered ring formation. (+/-)-Supinidine is prepared using this methodology.