Reactions of the ketone derived from (±)-3,4,5-tri-O-benzyl-1,2-O-isopropylidene-myo-inositol: preparation of racemic derivatives of epi-inositol and of 4-C-methyl-epi- [(±)-iso-laminitol] and 4-C-methyl-myo-inositol [(±)-laminitol]