Structures of three disubstituted [13]-macro-di-lac-tones reveal effects of substitution on macrocycle conformation

The synthesis and crystal structures of three new disubstituted [13]-macro-di-lactones, namely, trans-4,8-dimethyl-1,10-dioxa-cyclo-tridec-5-ene-2,9-dione, C₁₃H₂₀O₄, I, cis-4-(4-bromo-phen-yl)-13-methyl-1,10-dioxa-cyclo-tridec-5-ene-2,9-dione C₁₈H₂₁BrO₄, II, and trans-11-methyl-4-phenyl-1,10-dioxa-cyclo-tridec-5-ene-2,9-dione, C₁₈H₂₂O₄, III, are reported and their conformations are put in the context of other [13]-macrodilactone structures reported previously. Together, they show that the number, location, and relative disposition of groups attached at the termini of planar units of the [13]-macrodilactones subtly influence their aspect ratios.