Successful Combination of (Methoxydimethyl)methyl (MIP) and (2-Naphthyl)methyl (NAP) Ethers for the Synthesis of Arabinogalactan-Type Oligosaccharides

Abstract

In order to characterise the presumed epitopes of arabinogalactans, isolated from the extract of the cell-cultured Echinacea purpurea, two oligosaccharides were synthesized. The whole synthetic route was based on the successful combination of the (methoxydimethyl)methyl (MIP) and the (2-naphthyl)methyl ether (NAP) protecting groups. A β-(1→6)-linked trigalactoside was prepared, which contained a NAP ether at position 2′.This protecting group was selectively removed using either DDQ or Pd-C/H2 and the acceptor was ready for further glycosylation.We have used two arabinofuranosyl donor compounds: 2,3,5-tri-O-acetyl arabinofuranosyl trichloroacetimidate and a peracetylated α-(1→5)-linked diarabinofuranosyl trichloroacetimidate. For the deprotection of the tetra- and pentasaccharides a common procedure was used. All of the synthesized compounds were characterized by 1H and 13C NMR spectroscopy, as well as by MALDI-TOF mass-spectrometry.