The first enantioselective synthesis of imino-deoxydigitoxose and protected imino-digitoxose by using L-threonine aldolase-catalyzed aldol condensation

摘要

The first enantioselective synthesis of protected imino-digitoxose (-)-16 was attained Starting with a synthetic intermediate of polyoxin C prepared by the L-threonine aldolase-catalyzed aldol condensation of (2S,3S)-2,3-O-isopropyriden-4-penten-1-al 8 and glycine. The strategy took advantage of an intramolecular nucleophilic attack by a Cbz-protected amino group on the hemiacetal Carbon, a side reaction in the synthesis of natural products, for the formation of the piperidine ring of the imino-sugar. Imino-deoxydigitoxose (+)-18 was also synthesized from (-)-16 by reduction and acid hydrolysis.