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Biogenetically related caged ent-kaurane diterpenoids from Isodon eriocalyx var. laxiflora
- Wang, Wei-Guang, Li, Xiao-Nian, Du, Xue, Dong, Ke, Zhao, Wei, Wu, Hai-Yan, Kong, Ling-Mei, Li, Yan, Pu, Jian-Xin, Sun, Han-Dong
- Tetrahedron letters 2012 v.53 no.22 pp. 2777-2781
- X-ray diffraction, chemical reactions, chemical structure, cytotoxicity, diterpenoids
- Two novel caged ent-kauranoids, neolaxiflorins D (1) and E (2), along with three other new ent-kauranoids, neolaxiflorins F–H (3–5), and a known one, eriocalyxin B (6), were obtained from Isodon eriocalyx var. laxiflora. Neolaxiflorin D (1) is the first 15,16-seco-16,17-dinor-ent-kaurane diterpenoid, and neolaxiflorin E (2) is the first 15,16-seco-17-homo-ent-kauranoid. The absolute configurations of ent-kauranoids 1 and 2 were determined by single-crystal X-ray diffraction analyses. Structural analysis of intermediate compounds 3–5 indicated that eriocalyxin B (6) is a biogenetic precursor of caged ent-kauranoids 1 and 2 as illustrated. The cytotoxic activity of the new compounds was evaluated by an MTT assay.