α-D-Fucopyranose (aka α-D-fucose) is a six-carbon deoxy monosaccharide. It is equivalent to 6-deoxy-D-galactose. It acts as a non-metabolizable analog of L-arabinose and inhibits induction of the L-arabinose operon in some bacteria. Other bacteria possess a mutant araC gene where D-fucose acts as a gratuitous inducer of the L-arabinose operon. D-fucose also acts as an activator of the galS promotor in E. coli. Because of its ability to regulate gene expression, there has been some interest in exploring D-fucose as a lead compound in neurodegenerative diseases or cancer.

L-fucose is a hexose deoxy sugar found on N-linked glycans on mammalian, insect and plant cell surfaces. Deficiency in L-fucose has been observed in several pathological conditions including cancer and atherosclerosis. On the other hand, L-fucose is an inhibitor of the sodium/myo-inositol transporter which may play a roll in the development of diabetes. L-fucose is has been considered as a diagnostic biomarker in several forms fo cancer.