Two efficient ways to 2-O- and 5-O-feruloylated 4-nitrophenyl α-l-arabinofuranosides as substrates for differentiation of feruloyl esterases

4-Nitrophenyl 2-O-(E)-feruloyl-α-l-arabinofuranoside 1 and 4-nitrophenyl 5-O-(E)-feruloyl-α-l-arabinofuranoside 2 have been synthesized by two different routes. Monoferuloylation was accomplished by a chemoenzymatic sequence employing a regioselective transesterification catalyzed by lipases. The feruloyl group was introduced to enzymatically prepared 2,3- and 3,5-diacetates of 4-nitrophenyl α-l-arabinofuranoside by reaction with 4-O-acetylferuloyl chloride. Removal of the protecting acetyl groups yielded 1 and 2. An alternative chemical synthesis suitable for preparation of larger quantities of 1 and 2 also is presented. The new substrates represent convenient tools to differentiate feruloyl esterases on the basis of their substrate specificity.