Turnera ulmifolia L. is a shrubby perennial, tropical American plant that has been reported cyanogenic by [1]. The Turneraceae has long been considered to be closely related to the Passifloraceae and Flacourtiaceae [2,3]. Members of the latter two families are unique in producing cyclopentenoid cyanogens. Gynocardin has been isolated from the Flacourtiaceae [4], and gynocardin, tetraphyllin A, tetraphyllin B (barterin), epi-tetraphyllin B and deidaclin have been isolated from the Passifloraceae [1,5-9]. In reporting the isolation of deidaclin from Turnera ulmifolia, we offer further evidence of the affinity of the Turneraceae with the Passifloraceae and Flacourtiaceae. This is only the second report of deidaclin from a natural source. The NMR spectrum of the TMS ether of the unknown (Fig. 1) proved to be identical with that of the TMS ether of deidaclin previously reported [9]. The presence of a single glucose unit as the sugar moiety of the cyanogen was confirmed by the glucose oxidase method. The field desorption MS (source temperature 100°) of the unknown showed strong peaks at m/e 272 (M + 1), 245 (M-26), 163 and 164 and a doublet at m/e 92 and 93. These data are consistent with those of refs. [8] and [9].