Rearranged Phloroglucinol-Monoterpenoid Adducts from <i>Callistemon rigidus</i>

Callisretones A (1) and B (2), two rearranged phloroglucinol-monoterpenoid adducts featuring an unprecedented isopropylcyclopenta­[b]­benzofuran backbone, together with their postulated biosynthetic precursors (3–9), were isolated from Callistemon rigidus. The previously assigned absolute configurations of viminalins H (7), L (8), and N (9) were revised and unequivocally established by X-ray diffraction data. A putative biosynthetic pathway toward callisretones A and B involving the rearrangement of the terpenoid motif is proposed. In addition, 1 and 2 showed inhibitory effects on nitric oxide production with IC50 values of 15.3 ± 1.0 and 17.7 ± 1.1 μM, respectively.从红千层（Callistemon rigidus）中分离得到2个重排型间苯三酚-单萜（phloroglucinol-monoterpenoid）加合物——卡利斯特酮A（Callisretones A）（1）与卡利斯特酮B（Callisretones B）（2），二者拥有前所未有的异丙基环戊并[b]呋喃（isopropylcyclopenta[b]benzofuran）骨架；同时还分离得到了其推定的生物合成前体（3~9）。此前被指定的维米那素（viminalins）H（7）、L（8）与N（9）的绝对构型被修正，并通过X射线衍射（X-ray diffraction）数据得到了明确确证。本文提出了一条涉及萜类骨架重排的、通向卡利斯特酮A与B的推定生物合成途径。此外，化合物1与2对一氧化氮生成具有抑制活性，其半最大抑制浓度（IC50）分别为15.3 ± 1.0 μM与17.7 ± 1.1 μM。