Fucose spectroscopy

Additional evidence for an alternative pathway for the production of L-fucose came from experiments in mouse lymphoma cell lines blocked in the conversion of GDP-D-[ H]-mannose to GDP-L-[ H]-fucose. Reitman et al. observed that the block could be bypassed by growing the cells in the presence of L-fucose [119]. That this short activation pathway may be a general salvage mechanism is also indicated by the fact that 6-deoxy-D-glucose derivatives could be incorporated into neomycin [71]. The existence of a short activation pathway was recently proven in our laboratories [120] by successful incorporation of l-[2, 3--H2]-rhodinose [121] into landomycin A (12). In this experiment, NMR spectroscopy of the product showed, that only the four protons of the two L-rhodinose moieties were labeled. In a control experiment, d-[2, 2, 3, 3- H4]-rhodinose [121] was fed and, as expected, no incorporation into 12 was observed [120] (Scheme 27). 

A polysaccharide (mol. wt. 9.5 x 10 ) containing residues of D-galactose, D-mannose, and L-fucose (12 3 4) has been purified from the fruiting bodies of Flammulina velutipes. The structure (23) is based on the results of methyla-tion analysis, i.r. spectroscopy, and interaction studies with concanavalin A. Every third (1 -> 6)-linked a-D-galactopyranosyl residue is substituted with either an L-fucopyranosyl group or a 3-0-a-D-mannopyranosyl-L-fucopyranosyl unit. 

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