Abstract Partially methylated and acetylated 3-deoxyoctitols and 3-deoxyheptitols were prepared from synthetic derivatives of 3-deoxy- d -manno-octulosonic acid and 3-deoxy- d -arabino-heptulosonic acid, espectively, by derivatisation procedures used in methylation analysis (hydrolysis, carbonyl- and carboxyl-reduction, methylation, and acetylation). The compounds so obtained were characterised by