Korea Institute of Ocean Science & Technology (KIOST), Busan 49111, Korea.
Department of Marine Biotechnology, University of Science & Technology, Daejeon 34113, Korea.
Mar Drugs. 2020 Nov 30;18(12):607. doi: 10.3390/md18120607.
A total of eight new oxygenated 4--methylene sterols, -, together with one artifact and six known sterols -, were isolated from the marine sponge collected from the Bohol province in Philippines. Structures of sterols - were determined from 1D and 2D NMR data. Among the sterols, 8-hydroxytheonellasterol () spontaneously underwent an allylic 1,3-hydroxyl shift to produce 15-hydroxytheonellasterol () as an artifact; this was rationalized by quantum mechanical calculations of the transition state. In addition, the 1,2-epoxy alcohol subunit of 8-hydroxy-14,15--epoxytheonellasterol () was assigned using the Gauge-Independent Atomic Orbital (GIAO) NMR chemical shift calculations and subsequent DP4+ analysis. Finally, comparison of the C chemical shifts of isolated 7-hydroxytheonellasterol () with the reported values revealed significant discrepancies at C-6, C-7, C-8, and C-14, leading to reassignment of the C-7 stereochemistry in the known structure.
从菲律宾薄荷省采集的海绵中分离得到了八种新型含氧 4--亚甲基甾醇、-，以及一种副产物和六种已知甾醇、-。甾醇-的结构通过 1D 和 2D NMR 数据确定。在这些甾醇中，8-羟基异石胆甾醇（）自发经历烯丙基 1,3-羟基移位，生成作为副产物的 15-羟基异石胆甾醇（）；这可以通过过渡态的量子力学计算来合理化。此外，使用 Gauge-Independent Atomic Orbital (GIAO) NMR 化学位移计算和随后的 DP4+分析，确定了 8-羟基-14,15--环氧异石胆甾醇（）中 1,2-环氧醇亚基的位置。最后，与报道值相比，分离得到的 7-羟基异石胆甾醇（）的 C 化学位移存在显著差异，特别是在 C-6、C-7、C-8 和 C-14 处，导致已知结构中 C-7 立体化学的重新分配。
