[(2R,5R,6S,9R)-6-Isopropyl-9-methyl-1,4-dioxaspiro­[4.5]decan-2-yl]methyl 4-bromo­benzoate

The title compound, C(20)H(27)BrO(4), a 4-bromo­benzoyl derivative of a stereoisomer of glycerol menthonide, synthesized as part of a study of 3-carbon stereochemical moieties, crystallizes with two crystallographically independent mol­ecules in the asymmetric unit, the two mol­ecules differing only in one of the C—O—C—C torsion angles around the ester O atom [−106.5 (7) and 146.1 (6)°]. The two mol­ecules are crystallographically related by a pseudotranslation along the (011) diagonal of the unit cell, emulating a primitive monoclinic cell of half the volume. The translational symmetry is broken by the 4-bromo­benzoate groups. The crystallographic assignment of the absolute stereochemistry is consistent with having started with (−)-menthone, the acetal C atom is R and the secondary alcohol is R. This brings the bromo­benzoate into approximately the same plane as the menthyl ring and cis to the isopropyl group. The glycerol menthonide sections of the molecules interact with each other via C—H⋯O interactions, leading to the formation of chains either A or B molecules that stretch parallel to [010], forming column-shaped double chains. Interactions between neighboring columns are limited to van der Waals contacts.