Indirect Enzymatic Assay of D-galactofuranosides of 4-nitrocatechol with an Exoglycosidase from Radish (Raphanus sativus L.) Germs

摘要

alpha- And beta-L-arabinofuranosides of 4-nitrocatechol were synthesized by a modified Helferich method in the presence of BF3 center dot OBu2 as promoter. beta- and alpha-D-galactofuranosides of 4-nitrocatechol were synthesized by Michael method as modified by Mannich, from tetra-O-benzoyl-alpha-D-galactofuranosyl bromide and 4-nitrocatechol. The latter diastereomeric synthetic glycosides were submitted to oxidation with periodic acid (Malaprade reaction). The new formed aldehyde function was reduced with sodium borohydride and the produced L-arabinofuranosides were chromatographically compared with those directly synthesized and then put in interaction with an enzymatic extract from radish (Raphanus sativus L.) germs. In this way it was indirectly proved that 4-nitrocatechol galactosides syntesized possessed furanosic ring and can be used as substrates for galactofuranosidases.