Asymmetric Total Synthesis of (+)-Karanone: An Important Aroma Compound in Fine Agarwood

The first asymmetric total synthesis of (+)-karanone, a key aroma compound in high-grade agarwood (“Kyara”), was accomplished in 17 steps from 4-penten-2-ol. The key stereocenters at C7, C4, and C5 were introduced via asymmetric aldol condensation and Ireland–Claisen rearrangement. The oxygen-functional group at C8 was formed through oxidative rearrangement, and the bicyclic core of (+)-karanone was constructed by ring-closing metathesis. Two related compounds, namely (+)-4-epi-karanone and (+)-warburgiadione, were also synthesized. Studies of the structure–odor relationship among (+)-karanone, (+)-4-epi-karanone, and (+)-warburgiadione were also performed.

高档沉香（俗称奇楠，Kyara）中的关键香气成分(+)-卡兰酮（(+)-karanone）的首例不对称全合成，以4-戊烯-2-醇为起始原料，经17步反应完成。C7、C4与C5位的关键手性中心通过不对称羟醛缩合与爱尔兰-克莱森重排反应构建；C8位的氧官能团经由氧化重排反应引入，而(+)-卡兰酮的双环核心则通过关环复分解反应组装。本研究同时完成了两种相关化合物——(+)-4-表卡兰酮（(+)-4-epi-karanone）与(+)-瓦堡二酮（(+)-warburgiadione）的全合成，并对(+)-卡兰酮、(+)-4-表卡兰酮及(+)-瓦堡二酮的结构-气味相关性开展了系统研究。