摘要
Kalmane diterpenoids,featuring a 5/8/5/5 tetracyclic carbon skeleton,are very rare in nature.The flowers of Rhododendron dauricum L.(Ericaceae)were phytochemically investigated for the first time,leading to the isolation of eight kalmane diterpenoids(1-8)including four new ones,named rhodokalmanols A-D(1-4).The structures of 1-8 were elucidated by comprehensive spectroscopic methods and ic NMR-DP4+analysis,and the absolute configurations of 1,2,4,and 5 were defined by single-crystal X-ray diffraction analysis with Cu Kαradiation.Rhodokalmanol A(1)represents the first 5,8-epoxykalmane diterpenoid and also the first kalm-15(16)-ene diterpenoid.Rhodokalmanols BD(2-4)are the first examples of kalm-7(8)-ene,kalm-16(17)-ene,and 8α-methoxykalmane diterpenoids,respectively.All the isolated kalmane diterpenoids 1-8 exhibited significant analgesic effects,and rhodokalmanol C(3)and kalmanoi(8)expressed more potent analgesic activity than morphine at doses of 0.2 and 0.04 mg/kg.The preliminary structure-activity relationships of kalmane diterpenoids as potent analgesics are discussed.
基金
This work was financially supported by the Scientific Research Project of Traditional Chinese Medicine of Hubei Provincial Health Commission(ZY2021M056)
the Open Project of State Key Laboratory of Chemistry and Molecular Engineering of Medicinal Resources(No.CMEMR-2021-B03)。