Baccaramiones A–D, Four Highly Oxygenated and Rearranged Trinorditerpenoids from <i>Baccaurea ramiflora</i>
Shu-Shuai Chen, Xiao Tong, Xiangyu Liu, Cheng‐Yu Zheng, Jun‐Su Zhou, Yao‐Yue Fan, Shijun He, Bin Zhou, Jian‐Min Yue
Abstract
Baccaramiones A–D (1–4), four highly oxygenated and rearranged trinorditerpenoids, were isolated from Baccaurea ramiflora. Compound 1 is a 1(10 → 5)-abeo-15,16,17-trinor-ent-abietane featuring a unique 5/6/6 spirocyclic scaffold, and 2–4 are the first example of a novel 20(10 → 5)-abeo-15,16,17-trinor-ent-abietane skeleton. Their structures were established by spectroscopic analysis, X-ray crystallography, and electronic circular dichroism calculations. A plausible biosynthetic pathway for 1–4 was proposed. Interestingly, compounds 3 and 4 exhibited significant immunosuppressive activities against concanavalin A-induced T cell proliferation and lipopolysaccharide-induced B cell proliferation in vitro.