Bioactive sesquiterpenes from Santolina rosmarinifolia subsp. canescens. A conformational analysis of the germacrane ring - Barrero, A F; Herrador, M M; Quilez, J F; Alvarez-Manzaneda, R; Portal, D; Gavin, J A; Gravalos, D G; Simmonds, M S; Blaney, W M (Phytochemistry, 1999)