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.