A 3,5-dinitro­benzoyl derivative of a stereoisomer of glycerol menthonide

The title compound, [(2S,5R,6S,9R)-6-isopropyl-9-methyl-1,4-dioxaspiro-[4.5]dec-2-yl]methyl 3,5-dinitro-benzoate, C(20)H(26)N(2)O(8), was synthesized as part of a study of three-carbon stereochemical systems. The crystallographic assignment of the absolute stereochemistry is consistent with having started with (-)-menthone, the acetal carbon is R and the secondary alcohol is S. This brings the dinitro-benzoate into approximately the same plane as the menthyl ring and anti to the isopropyl group. Close inter-molecular C=O⋯NO(2) contacts between neighboring mol-ecules [2.8341 (16) Å] contribute to the packing arrangement. The structure was refined as a pseudo-merohedral twin (monoclinic space group P2(1) emulating the ortho-rhom-bic space group C222(1)). Application of the twin law 100, 00, 0 gave a 2:1 ratio of twin moieties [refined BASF value = 0.3790 (7)].