6,6-Di-C-alkyl-d-galactopyranoses. A new group of liquid crystalline compounds forming columnar phases [1]

The geminally C-branched 6,6-di-C-n-alkyl-d-galactopyranoses 3a–d prepared in two steps from 1,2:3,4-di-O-isopropylidene-d-galacturonic acid methylester 1 and the even numbered C8-C12-alkylmagnesium bromides, represent a new group of ‘double tailed’ thermotropic mesogens forming columnar supramolecular structures based on hydrogen bridged (disc-like) multimers in accordance with the hypothesis of the Praefcke group. Furthermore, the thermal behaviour of the homologous 6-O-alkyl-d-galactopyranoses 4a–e is discussed in connection with the revised model for the molecular arrangement in smectic A phases of ‘single tailed’ carbohydrates.