Preparation of regioselectively feruloylated p-nitrophenyl alpha-L-arabinofuranosides and beta-D-xylopyranosides-convenient substrates for study of feruloyl esterase specificity.

p-Nitrophenyl alpha-L-arabinofuranoside and beta-D-xylopyranoside mono-O-ferulates were prepared by 4-O-acetylferuloylation of corresponding enzymatically prepared di-O-acetates followed by deacetylation. An alternative mild acylation catalysed by zinc oxide was tested on xylopyranoside derivatives. The chemoselective methanolysis of the acetyl groups using neutral catalyst dibutyltin oxide at reflux was used as deacetylation method. Under these conditions a significant feruloyl migration was observed mainly on p-nitrophenyl 3-O-feruloyl-beta-D-xylopyranoside resulting in low yields of the positional isomers. Investigation of substrate and positional specificity of different types of feruloyl esterases on the presented compounds in enzyme-coupled assays was reported previously.