Radical cyclisation studies of chiral α-acylamino radicals : a model study towards Tacaman indole alkaloid synthesis

he radical cyclisation of chiral 4,5-substituted N-acyl-2-aza-6-heptenyl radicals, derived from D-ribose, has been undertaken as a model stuay towards Tacaman indole alkaloid synthesis. The radical cyclisations were conducted using tributyltin hydride/AIBN in refluxing benzene. The α-acylamino radicals added to double bonds which were activated by an ethoxycarbonyl substituent. No reduction of the radicals by the tributyltin hydride was observed. Those radicals incorporating an isopropylidene ketal at the 4 and 5 positions as chiral auxiliary showed excellent regio- and stereoselectivity. Out of a possible 4 diastereomers, only two were obtained in a 2:8 ratio. It was established that the isopropylidene ketal directed the cyclisation stereoselectively and that no stereoselectivity was observed in the absence of the chiral auxiliary.

Grantor dc:publisher.institution

Department of Chemistry

Year dc:date.issued

1996

Author dc:creator

• Clauss, Rainer

Advisor dc:contributor.advisor

• Hunter, Roger

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/16138

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/16138