Elongation of the pentose chain at the terminal carbon atom with Grignard C1 reagents. A study of the homologation reaction

Article abstract of DOI:10.1016/S0040-4020(99)00197-0

Derivatives of four stereoisomeric pentodialdo-1,4-furanoses were reacted with four Grignard C₁ reagents: methoxymethyl-, allyloxymethyl-, benzyloxymethyl, and dimethylphenylsilylmethyl-magnesium chlorides. Derivatives of the expected stereoisomeric hexoses were accompanied in some cases by C-4 inverted products. The results have been discussed in terms of α- and β-chelated transition states. It has been found that the RX (X=O,Si) grouping of the Grignard reagent strongly influences the stereochemical outcome of the elongation reaction.