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Harringtonolide (5) has excellent anti-KB tumor activity (IC50 = 43nm)
Figure 1.
Recently, Hongbin Di’s research group of Peking University Shenzhen Graduate School achieved the first asymmetric total synthesis of (+)-mannolide C, a natural product of cephalotaxus diterpene
First, the readily available meso-anhydride 7 is used as a raw material to obtain rac-enol lactone 11 through nucleophilic addition and in-situ dehydration reaction
Figure 2.
The author screened and optimized the reaction conditions for the key transformation of double RCM, and obtained the expected core tetracyclic intermediate 10 (Figure 3)
entry | conditions | result |
1 | HG 2nd catalyst, Ar, 90 °C | no desired product |
2 | HG 2nd catalyst, ethylene, 90 °C | no desired product |
3[a] | HG 2nd catalyst, 18, 90 °C | 10 (trace) |
4 | HG 2nd catalyst, 18, 110 °C | 10 (45%) |
5 | HG 2nd catalyst, 18, 130 °C | 10 (25%) |
6 | HG 2nd catalyst, 18, microwave, 110 °C | 10 (30%) |
7 | HG 2nd catalyst, microwave, 110 °C | 10 (50%) |
8[b] | HG 2nd catalyst, microwave, 150 °C, 30 min | 10 (70%) |
9 | HG 2nd catalyst, microwave, 200 °C | decomposition |
[a] Additive 18 =2,3,5,6-Tetrafluorocyclohexa-2,5-diene-1,4-dione.
Figure 3.
Figure 4.
In summary, starting from meso-anhydride 7, and based on the dual RCM cyclization strategy, Zhai Hongbin's research group achieved the first highly efficient asymmetric total synthesis of (+)-mannolide C with 22 steps in total
The above work was mainly completed by the doctoral students Ao Qiaoqiao and Dr.