Isolation, Synthesis, and Structure-Activity Relationship Study on Daphnane and Tigliane Diterpenes as HIV Latency-Reversing Agents.

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 EC 50 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.