Synthesis of Leonosides E and F derived from Leonurus japonicas Houtt Original Research Article

Leonosides E and F, two natural phenylethanoid glycosides derived from Leonurus japonicas Houtt, which bear different trisaccharide moieties—one linear and one branched, were totally synthesized via a direct transglycosylation strategy. After trisaccharyl trichloroacetimidates 3 and 4 were prepared as glycosyl donors, they were coupled with the homovanillyl aglycon via silver triflate-promoted transglycosylation to successfully furnish the fully protected glycosides, which were globally deprotected to afford the target molecules in 6.77% and 10.08% overall yields for the longest linear synthetic sequence starting from 6 and 14.