Use of polystyrene-supported DBU in the synthesis and alpha-selective glycosylation study of the unstable Schmidt donor of L-kedarosamine.

In the alpha-glycosylation study of the unusual, 2-deoxy amino sugar of kedarcidin, polystyrene-supported DBU (PDBU) was found to be invaluable to the clean preparation of the highly labile Schmidt donor of l-kedarosamine. By further recognition that the C4-alcohol should be left free for favorable acceptor reactivity, we could for the first time successfully assemble the C13-O-alpha-glycoside of the ansamacrolide substructure of the kedarcidin chromophore. [reaction: see text]