The crystal structure and absolute configuration of lactucin

11β,13-Dihydrolactucin-8-O-acetate hemihydrate

“…The absolute configuration was determined by refinement of the Flack (1983) parameter, based on resonant scattering of the light atoms. It agrees with that of lactucin (Ruban et al, 1978) and with the accepted configuration of sesquiterpene lactones from higher plants (Fischer et al, 1979). Analysis of the Bijvoet pairs using the method of Hooft et al (2008) yielded y = 0.03 (4) for this structure, confirming the absolute configuration.…”

“…For phytochemical reports of the title compound, see: Bohlmann et al (1981); Djordjevic et al (2004); Sarg et al (1982); Song et al (1995). The crystal structures of several related compounds have been reported: 8--hydroxyachillin (Campos et al, 1989); matricarin (Parvez et al, 2002); lactucin (Ruban et al, 1978); lactucopicrin (Ren et al, 2003); absolute configuration of sesquiterpene lactones Fischer et al (1979). For analysis of Bijvoet pairs, see: Hooft et al (2008).…”

Complete NMR spectral assignments of two lactucin‐type sesquiterpene lactone glycosides from Picris conyzoides

“…The position of attachment of the sugar moiety at C‐15 was confirmed from the HMBC spectrum of compound 2 in which cross peaks between H‐1′ and C‐15 as well as between C‐1′ and H‐15a /H‐15b were observed. The stereochemistry of compound 2 was derived from vicinal 1 H, 1 H‐coupling constants, and NOESY data on the basis of the assumption that H‐7 is α, as established for the structurally related guaianolide lactucin of known absolute stereochemistry . The vicinal coupling constants of H‐5 to H‐9 and H‐11 in compounds 1 and 2 were essentially the same and NOESY spectra of both compounds displayed the expected correlations between H‐5 and H‐7 and H‐7 and Me‐13, and between H‐6 and H‐11, H‐8 and H‐11, and H‐8 and H‐9β, in agreement with the assignments shown in Fig.…”

Lettuce allergy: sensitizing potency of allergens

“…An explanation for the findings that only lactucin produced positive reactions in the patients (while lactucopicrin did not) and elicited strong cross-reactions in lactucopicrin-sensitive animals (while lactucopicrin elicited only weak cross-reactions in lactucin-sensitive guinea pigs) might lead to the suggestion that lactucin is the real sensitizer. The absolute configuration of lactucin (14) reveals that the hydroxy group in the C(8) position (Fig. 1) adjacent to the methylene of the lactone has no essential influence on the latter.…”