ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 49, Number 1
JKCSEZ 49(1)
February 20, 2005 

Intramolecular radical cyclizations of dehydroamino acid dipeptide derivatives were performed with various radical initiation methods and precursors. When the radical precursor was iodine, the reaction under the radical initiation condition with AIBN, Bu3SnH, and heating gave the cyclized product with high yield. However, the stereoselectivity of new forming stereocenter which was suppose to be controlled by the chiral auxiliary on the adjacent amino acid was low. In case of radical initiation with Et3B and Bu3SnH at -20 oC, much enhanced stereoselectivity was found with similar yield. The intramolecular radical cyclization of dehydroamino acid methyl ester which has a chiral center next to the double bond was also checked. High yield and affordable stereoselectivity was found but still unsatisfactory under the reaction condition with AIBN, Bu3SnH at 70 oC.