L-Fucose is ubiquitous in nature and its presence in glycoconjugates and other biologically important moieties plays an important role in the activity of these substances [1]. However, it is a quite expensive sugar. In the course of synthesis of some biologically active oligosaccharides, it was therefore deemed pertinent to develop an easy route for the synthesis of L-fucose from a readily available source.
Several methods for the synthesis of L-fucose have been reported [2][3][4][5]. Two of these methods used D-galactose as the starting material. The first one [4] involved a lengthy reaction sequence and low yield. The second method [5] had a shorter route but utilized expensive reagents and involved syrupy intermediates. The purpose of this communication is to report an easy and inexpensive route for the synthesis of L-fucose from D-galactose in good yield using inexpensive reagents and involving mostly crystalline intermediates.
D-Galactose diethyl dithioacetal [6] (1), obtained from D-galactose, was reduced [7] with Raney nickel in the presence of zinc granules and sodium hydroxide to afford L-fucitol (2). The use of zinc and NaOH reduced the requirement of Raney nickel to one-half while the yield increased threefold. L-Fucitol (2), thus obtained, was partially acetylated [8] with acetic anhydride (1.2 equiv) and pyridine, giving 1-O-acetyl-L-fucitol (3). The tetrabenzoate (4), obtained by benzoylation of 3, was then deacetylated [9] with