The synthesis of 3‐deoxy‐L‐fucose (3,6‐dideoxy‐L‐xylo‐hexose)
The synthesis of 3-deoxy-L-fucose (19) could not be achieved by an inversion procedure, starting from the 3-O-triflate-activated derivatives 8 or 9, respectively. Also the Mitsunobu reaction with the 3-OH-unblocked sugars 6 or 7 did not lead to the desired compounds. Instead, the formation of the unexpected side products 10, 11 and 12 was observed and interpreted. However, an equilibrium mixture of 3-deoxy-L-fucose 19 and 21 was successfully synthesized by utilizing a Barton-type deoxygenation of methyl 2,4-di-O-benzoyl-α-L-fucoside (7). The latter compound could be obtained from methyl α-L-fucoside (1) in a one-pot reaction and crystallization in approximately 70% yield.