Three new 5,10-epoxygermacranolides from Liatris chapmanii and Liatris gracilis

Examination of Liatris chapmanii (T + G) Kuntze led to the isolation of two new germacranolides, chapliatrin (1a) and isochapliatrin (1b). Liatris gracilis Pursh gave chapliatrin and acetylchapliatrin 1c). The stereochemistry assigned to C-3, C-4 and C-10 is tentative. All three compounds possess the hitherto-unreported 5,10-oxygen linkage. L. gracilis also gave the benzofuran euparin (2) and the flavones hispidulin (dinatin, 3a and 3′,6-dimethoxy-4′,5,7-trihydroxyflavone (3b). L. chapimanii also gave 5-hydroxy-3′,4′,6,7-tetramethoxyflavone (3c).