Bioorg Chem 2021 Mar 29;111:104870. Epub 2021 Mar 29.
Hubei Key Laboratory of Natural Medicinal Chemistry and Resource Evaluation, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China. Electronic address:
Seventeen diterpenoids (1-17), classified into eight diverse carbon skeleton types, grayanane (1, 2, and 12), micranthane (3, 4, and 13), mollane (5-7 and 14), 1,5-seco-grayanane (8), kalmane (9-11), 1,5-seco-kalmane (15), A-homo-B-nor-ent-kaurane (16), and leucothane (17), respectively, were isolated from the leaves extract of Rhododendron micranthum. Among them, diterpenoids 1-9 are new compounds and their structures were elucidated via extensive spectroscopic methods, quantum chemical calculations including the C NMR-DP4+ analysis and electronic circular dichroism (ECD) calculations, and the single-crystal X-ray diffraction analysis. Micranthanol A (1) represents the first example of a 5αH,9αH-grayanane diterpenoid and a 6-hydroxy-6,10-epoxygrayanane diterpenoid, and micranthanone B (3) is the first 6,10-epoxymicranthane and the 5α-hydroxy-micranthane diterpenoids. Read More