A new guaianolide from the roots of Pterocypsela elata

In order to find more biologically active substances,we have carefully investigated the chemical constituents of Pterocypsela elata.One new guaianolide,(4S)-11-methoxycarbonyl-guaiane- 1(10),5(6),7(11),8(9)-tetraen-6,l2-olide was isolated from the EtOAc extracts of the roots of P.elata. Its structure was elucidated by various spectroscopic methods and confirmed by X-ray crystallographic analysis.     

Stereochemistry of a Guaianolide from Cyathocline Purpurea by High Resolution NMR Spectroscopy

The stereochemistry of a sesquiterpene, 6α-hydroxy-4(14),10(15)-guaianadien-8β,12-olide (2) was established by high resolution and 2D-NMR spectroscopy. Careful analysis of the long range couplings along with vicinal spin-spin coupling constants predict a trans fusion of the lactone ring. Further information on the stereochemistry of 2 was obtained from 2D-NOESY and ROESY experiments.     

A Double Allylation Strategy for Gram‐Scale Guaianolide Production: Total Synthesis of (+)‐Mikanokryptin

With over 5000 members isolated to date, sesquiterpene lactones represent a prolific source of medicinal agents with several derivatives in human clinical trials. The guaianolides, a major subset of this group, have been intensely investigated from both medicinal and chemical‐synthesis perspectives for decades. To date, the myriad stereochemical permutations presented by this enormous family have precluded the synthesis of many unique members. Herein we report the total synthesis of the trans ‐fused 8,12‐guaianolide (+)‐mikanokryptin in 10 steps from (+)‐carvone. Notably, this synthesis is the first gram‐scale total synthesis of a guaianolide natural product.     

A Guaianolide Sesquiterpene,a Chromenone,and a Flavanone from Ligularia macrophylla

Three new compounds, (5β,9β)‐guaia‐6,10(14)‐dien‐9‐ol (=rel‐(1R,3aS,5R,8aR)‐1,2,3,3a,4,5,6,8a‐octahydro‐1‐methyl‐4‐methylene‐7‐(1‐methylethyl)azulen‐5‐ol; 1 ), 6‐acetyl‐8‐methoxy‐2,3‐dimethylchromen‐4‐one (=6‐acetyl‐8‐methoxy‐2,3‐dimethyl‐4H‐1‐benzopyran‐4‐one; 2 ), and (2S)‐3′‐hydroxy‐5′,7‐dimethoxyflavanone (=(2S)‐2,3‐dihydro‐2‐(3‐hydroxy‐5‐methoxyphenyl)‐7‐methoxy‐4H‐1‐benzopyran‐4‐one; 3 ) were isolated from the roots and rhizomes of Ligularia macrophylla, together with seven known compounds. Their structures and configurations were elucidated by spectroscopic methods, including 2D‐NMR techniques.