31] Linkage analysis using reductive cleavage method

Abstract

Publisher Summary This chapter discusses linkage analysis using reductive cleavage method. The relatively recently introduced technique of reductive cleavage allows the simultaneous determination of position(s) of linkage and ring form(s) in polysaccharides. The technique is based on methylation analysis, but departs from it significantly with regard to the types of fragments ultimately analyzed. In standard methylation analysis, the fully methylated polysaccharide is hydrolyzed, and the partially methylated sugars so formed are reduced (NaBH 4 ) and acetylated, and then characterized by gas-liquid chromatography-mass spectrometry. Total reductive cleavage is performed with triethylsilane as the reducing agent and with either trimethylsilyl trifluoromethane sulfonate (TMSOTf) or a mixture of trimethylsilylmethane sulfonate (TMSOMs) and boron trifluoride etherate (BF 3 • Et 2 O) as the catalyst. Reductive cleavage with Et 3 SiH and TMSOTf and subsequent in situ acetylation are accomplished as previously described in this series. The fragmentation patterns for derivatives of this type have not been established, but inspection of the spectra reported herein reveals diagnostic differences based upon the presence or absence of only a few ions in the spectra.