Supramolecular aggregation of two hydroxycarboxylic acid derivatives

The crystal structures of 7,7‐dicyclobutyl‐5‐hydroxymethyl‐6‐oxabicyclo[3.2.1]octane‐1‐carboxylic acid, C 17 H 26 O 4 , (I), and 1‐(hydroxymethyl)‐7‐oxaspiro[bicyclo[3.2.1]octane‐6,1′‐cyclopentane]‐5‐carboxylic acid, C 13 H 20 O 4 , (II), determined at 170 K, show that the conformation of the hydroxymethyl group ( anti or gauche ) affects the dimensionality (one‐ or two‐dimensional) of the supramolecular structures via O—H⋯O hydrogen bonds. In (I), the carboxyl and hydroxymethyl groups interact with themselves, forming a one‐dimensional step‐ladder, while in (II), a two‐dimensional structure is made up of carboxylic acid centrosymmetric R 2 2 (8) dimers connected by hydroxyl‐to‐ether contacts.