29Si chemical shifts and additivity in pertrimethylsilylated O-methyl,O-benzyl,O-benzoyl and O-acetyl methyl β-D-xylopyranosides

²⁹Si chemical shifts in pertrimethylsilylated O-methyl, O-benzoyl, O-benzoyl and O-acetyl methyl β-D -xylopyranoside derivatives are reported. The chemical shifts in monotrimethylsilyl derivatives with the same O-substituents are in the order: δ(Si-2) > δ(Si-4) > δ(Si-3). When the chemical shifts in bis (trimethylsilyl) and tris(trimethylsilyl) derivatives are assigned according to this rule, all the chemical shifts agree well with a direct additivity rule. The only significant deviation from additivity occurs for methyl 2,4-di-O-benzoyl-3-O-trimethylsilyl-β-D -xylopyranoside, which has a different average conformation from the other compounds studied.