The periodate-oxidised methyl glycosides of β-L-arabinopyranose and α-L-rhamnopyranose and periodate-oxidised benzyl β-L-arabinopyranoside have been used as the dialdehyde components in the Robinson–Schöpf condensation, yielding analogues of 9-methyl-3-oxagranatan-7-one. Comment is made on the ultraviolet spectra of these compounds.