A monoclinic form of dendocarbin A: a borderline case of one‐dimensional isostructural polymorphism

The title compound, dendocarbin A [systematic name: (1 R ,5a S ,9a S ,9b R )‐1‐hydroxy‐6,6,9a‐trimethyldodecahydronaphtho[1,2‐ c ]furan‐3‐one], C 15 H 22 O 3 , is a sesquiterpene lactone isolated from Drimys winteri var chilensis . The monoclinic phase described herein displays an identical molecular structure to the orthorhombic phase that we reported previously [Paz Robles et al. (2014). Acta Cryst. C 70 , 1007–1010], while varying significantly in chain pitch, and can thus be considered as a borderline case of one‐dimensional isostructural polymorphism.