Kunming Plant Institute has made new progress in the discovery and biomimetic total synthesis of novel diterpenes of Camellia sinensis plants

In order to lay the material foundation for in-depth functional research on this type of compound in the later stage, and to explore a new method for synthesizing spiro[4.
5]decane fragments, this task force carried out biomimetic total synthesis research
.
Core reaction strategies include iridium-catalyzed asymmetric polyene cyclization and half-frequency narol rearrangement
.
Using commercially available 3-methoxybenzaldehyde as the starting material, with the help of the asymmetric polyene cyclization strategy developed by Erick M.
Carreira's research group, 6/6/6 was obtained with a 4-step reaction and a yield of 35%.
Parallel ring intermediate 8
.
After a 6-step reaction, the construction
of precursor 12 was rearranged from 8 to half-frequency narol.
Although two tertiary alcohols are present in the structure of intermediate 12, C-13 is in the diallyl region, so the C-13 position is carbon-positive ratio C-9 carbocations are more stable
.
When the C-13 position carbocation is formed, the C-8/C-14 double bond can spontaneously migrate to the C-13/C-14 position.
Thus forming structural fragments of conjugated diene within the molecule, which are further rearranged by half-frequency narol into spirocyclic compounds15
.
Fortunately, boron trifluoride is at 0.
35 equivalents Ether Catalyzed, the researchers realized the skeleton rearrangement process from 6/6/6 parallel ring intermediate 12 to spiro[4.
5]decane intermediate 15
。 Subsequently, after 4 steps of late functional group modification, the biomimetic total synthesis of the target molecule rugosiformisin A was achieved (15 steps) (Fig 2）
。