Structures of three disubstituted [13]-macro­di­lac­tones reveal effects of substitution on macrocycle conformation

The synthesis and crystal structures of three new disubstituted [13]-macro­di­lactones, namely, trans-4,8-dimethyl-1,10-dioxa­cyclo­tridec-5-ene-2,9-dione, C13H20O4, I, cis-4-(4-bromo­phen­yl)-13-methyl-1,10-dioxa­cyclo­tridec-5-ene-2,9-dione C18H21BrO4, II, and trans-11-methyl-4-phenyl-1,10-dioxa­cyclo­tridec-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.