Synthesis and spectroscopic characterization of hydroxycinnamoylated methyl alpha-L-arabinofuranosyl-(1-->2)- and (1-->3)-beta-D-xylopyranosides.

A reaction sequence for the preparation of methyl 5-O-feruloyl-alpha-L- arabinofuranosyl-(1-->3)-beta-D-xylopyranoside, the companion 5-O-p-coumaroyl disaccharide, and their (1-->2) analogs has been developed. The (1-->3) hydroxycinnamoylated disaccharides are available in 11 steps from L-arabinose and methyl beta-D-xylopyranoside in 17% overall yield (based on methyl beta-D-xylopyranoside). The corresponding (1-->2) materials were prepared in 9 steps in > 37% overall yield. Complete spectral characterization provides unambiguous assignments for comparison with analogous materials isolated from plant cell-walls. Conformational aspects of the prepared materials are discussed in relation to coupling-constant information.