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

Abstract

The title compound, C(20)H(27)BrO(4), a 4-bromo-benzoyl derivative of a stereoisomer of glycerol menthonide, synthesized as part of a study of 3-carbon stereochemical moieties, crystallizes with two crystallographically independent mol-ecules in the asymmetric unit, the two mol-ecules 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 mol-ecules 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-bromo-benzoate 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 bromo-benzoate 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.

Fig. 1.

Displacement ellipsoid style view of the two molecules A and B of the title compound. Ellipsoid probability is at the 50% level.

Fig. 2.

Overlay of the two crystallographically independent molecules.

Fig. 3.

Packing view of the title compound, view down the (0 1 1) diagonal showing the pseudotranslation. Molecules A are shown in red, molecules B in blue.

Fig. 4.

Packing view of the title compound with intermolecular C—H···O interactions shown (blue dashed lines). Molecules A are shown in red, molecules B in blue.

Fig. 5.

Q-peaks (yellow spheres) caused by correlation effects due to pseudo-translation and their positions with respect to the Br atoms (green smaller spheres). Q1, located close to Br1, is created by translation of Br2 and Q2 by translation of Br1 by half a unit cell along the (0 1 1) direction. View is down the direction of the pseudotranslation as in Fig. 3.