Stereoselectivity in the epoxidation of carbohydrate based oxepines

ORGN 109

Shankar D. Markhad, shankar.markad@yahoo.com and Mark W. Peczuh, mark.peczuh@uconn.edu. Department of Chemistry, University of Connecticut, 55 North Eaglewille Road, Storrs, CT 06269
Carbohydrate based oxepines are ring expanded homologues of glycals and could be stereoselectively epoxidized using a variety of epoxidizing agents such as dimethyldioxirane, m-chloroperbenzoic acid, and diarylsulfoxide in combination with triflic anhydride. The results indicate that epoxidation takes place anti to the substituents present on the seven-membered oxacyclic molecular architecture nearly in all cases with good yields. It is believed that the high facioselectivity in the epoxidation is due to the stereoelectronic factors, which makes all substituents to orient in a pseudoequatorial manner and project away form the site of epoxidation.1 Our laboratory developed an efficient method for the synthesis of septanose sugars by Wittig olefination of lactol, vinyl etherification, ring closing metathesis, and oxirane formation followed by methanolysis.2 In continuation to our efforts, we plan to synthesize septanose sugars from hexoses and study their interactions with ConA. A detailed account of our results will be presented in the poster.