Asymmetric Total Synthesis of (+)-Phainanoid A and Biological Evaluation of the Natural Product and Its Synthetic Analogues

• Published in: Journal of the American Chemical Society 2023-03, Vol.145 (8), p.4828-4852
• Main Authors: Xie, Jiaxin, Zheng, Zhong, Liu, Xin, Zhang, Nan, Choi, Shinyoung, He, Chuan, Dong, Guangbin
• Format: Article
• Language: English
• Subjects: Biological Products - chemistry; Cell Survival; Immunosuppressive Agents - pharmacology; Stereoisomerism; Structure-Activity Relationship
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.2c13889

Here, we report our detailed efforts toward the synthesis of phainanoids, a novel class of dammarane-type triterpenoids with potent immunosuppressive activities and unique structural features. Systematic model studies have been carried out, and efficient approaches have been established to construct the benzofuranone-based 4,5-spirocycle, the D/E/F tricyclic core, the [4.3.1] propellane, and the 5,5-oxaspirolactone moieties. The asymmetric synthesis of (+)-phainanoid A has been achieved through kinetic resolution of the tricyclic core followed by diastereoselective installation of the A/B/C and G/H rings and fragment coupling with the enantioenriched I/J rings. In addition, novel estrone-derived phainanoid analogues have been prepared. The immunosuppressive and cell survival assays revealed that (+)-phainanoid A and some of its synthetic analogues can specifically inhibit stimulation-induced lymphocyte proliferation but not cell survival at their effective concentrations. Preliminary structure–activity relationship information has been obtained, which could inspire future design of immunosuppressive phainanoid analogues.