Isolation, Synthesis, and Structure–Activity Relationship Study on Daphnane and Tigliane Diterpenes as HIV Latency-Reversing Agents
Ahmed H. El‐Desoky, Keisuke Eguchi, Naoki Kishimoto, Toshifumi Asano, Hikaru Kato, Yuki Hitora, Shunsuke Kotani, Teruya Nakamura, Soken Tsuchiya, Teppei Kawahara, Masato Watanabe, Mikiyo Wada, Makoto Nakajima, Takashi Watanabe, Shogo Misumi, Sachiko Tsukamoto
Abstract
Three new diterpenes, stellejasmins A (1) and B (2) and 12-O-benzoylphorbol-13-heptanoate (3), were isolated from the roots of Stellera chamaejasme L. The structures of 1–3 were elucidated by extensive NMR and mass spectroscopic analyses. Compounds 1 and 2 are the first derivatives containing a hydroxy group at C-2 in the family of daphnane and tigliane diterpenes. The presence of a chlorine atom in 1 is unique in the plant metabolite. Compound 3 has an odd-number acyl group, which is biosynthetically notable. Human immunodeficiency virus (HIV) LTR-driven transcription activity was tested with 1–3 and 17 known diterpenes isolated from S. chamaejasme L. and Wikstroemia retusa A.Gray. Among these, gnidimacrin (4), stelleralide A (5), and wikstroelide A (20) were highly potent, with EC50 values of 0.14, 0.33, and 0.39 nM, respectively. The structure–activity relationship (SAR) was investigated using 20 natural and eight synthetic diterpenes. This is the first SAR study on natural daphnane and tigliane diterpenes.