posted on 2024-01-10, 22:07authored bySoumyakanta Maji, Balasaheb K. Ghotekar, Suvarn S. Kulkarni
Herein,
we report the first total synthesis of the tetrasaccharide
repeating unit of Vibrio cholerae O:3 O-antigen polysaccharide.
The highly complex tetrasaccharide contains rare amino sugars such
as d-bacillosamine and l-fucosamine, highly labile
sugar ascarylose, and higher carbon sugar d-d-heptose.
Stereoselective glycosylation of the notoriously reactive ascarylose
with d-d-heptose, poor nucleophilicity of the axial
C4-OH of l-fucosamine, and amide coupling are the key challenges
encountered in the total synthesis, which was completed via a longest
linear sequence of 23 steps in 4.2% overall yield.