## 2 The Phytochemistry of _Artemisia annua_ L. (Qinghao)
### Sesquiterpenenoids
#### 2.6.3. Bicyclic Sesquiterpenes  
2.6.3.1. Eudesmanes and Eremophilanes  
The bicyclic eudesmane sesquiterpenes (Table 34) are thought to be derived from further cyclization of the monocyclic germacranes (Table 31, Section 2.6.2). Eudesmanes are sometimes referred to as selinanes in the older literature and the most abundant eudesmane from _A. annua_ is \(\beta\)-selinene (**412**) [40,42]. The isolation of the eudesmane allylic hydroperoxide (**414**) from _A. annua_ is significant, as its structure is suggestive of formation by spontaneous autoxidation of the hydrocarbon precursor selina-4,11-diene (**422**) [9]. It has been suggested that reduction of the hydroperoxide in **414** would then result in the allylic alcohol group observed in the natural product 5\(\alpha\)-hydroxy-eudesmane-4(15),11-diene (**413**), as shown in Scheme 4 [9].  
**Scheme 4.** Postulated biogenesis of (**414**) and (**413**) by spontaneous autoxidation reaction of (**422**), followed by reduction.  
\begin{table}
\begin{tabular}{|l|l|l|l|} \hline
**Name** & **Alternative Name(s)** & **CAS Number** & **References** \\ \hline \(\beta\)-Selinene (**412**) & 4(15),11–Eudesmadiene & [17066-67-0] & [19, 23, 28, 30-32, 34, 40, 42, 43, 48, 113] \\ \hline \(5a\)-Hydroxy-eudesm-4(15),11-diene (**413**) & 4(15),11–Eudesmadien-5\(\alpha\)-ol & [9, 97] \\ \hline \(5a\)-Hydroperoxy-eudesma-4(15),11-diene (**414**) & & [9] \\ \hline \(19\),6\(\alpha\)-Dihydroxy-4(15)-eudesmane (**415**) & & [9] \\ \hline \(19\)-Hydroxy-4(15),5-eudesmadiene (**416**) & & [9] \\ \hline \(19\)-Hydro-4(15),7-eudesmadiene (**417**) & & [9] \\ \hline \(\gamma\)-Selinene (**418**) & 4(15),7(11)-Eudesmadiene & [515-17-3] & [45, 48] \\ \hline \(\beta\)-Eudesmol (**419**) & 4(15)-Eudesmen-11-ol & [473-15-4] & [45] \\ \hline \(\alpha\)-Selinene (**420**) & (5a,7\(\beta\),10\(\beta\))-\(\alpha\)-Eudesmane & [473-13-2] & [34, 111] \\ \hline \(3\),11-Eudesmadiene & & \\ \hline Kongol (**421**) & 11–Eudesm-4-ol(4\(\alpha\),5\(\alpha\),7\(\beta\),10\(\beta\)) & [16641-47-7] & [19, 27] \\ \hline Selina-4,11-diene (**422**) & Eudesma-4,11-diene & [17627-30-4] & [135] \\ \hline \(\gamma\)-Eudesmol (**423**) & 4-Eudesmen-11-ol & [1209-71-8] & [27] \\ \hline \(10\)-_epi-\(\gamma\)-Eudesmol (**424**) & 4-Eudemen-11-ol (7\(\beta\),10\(\alpha\)) & [15051-81-7] & [27, 45] \\ \hline Occidentalol (**425**) & 1,3-Eudesmadien-11-ol & [473-17-6] & [27] \\ \hline Occidentalol acetate (**426**) & & [346608-97-7] & [27] \\ \hline Occidol (**427**) & 1,2,3,4-Tetrahydro-\(\alpha\),\(\alpha\)-5,8- & [5986-36-7] & [27] \\ \hline Artemisin (**428**) & & & [141] \\ \hline \(a\)-Hydroxysantonin (**429**) & & & [142] \\ \hline \end{tabular}
\end{table}
Table 34: Eudesmane (Selinane) Sesquiterpenoids (Decahydro-1,4\(\alpha\)-dimethyl-7-(1-methylethyl))-naphthalene, 9 CI).  
The eremophilane skeleton (decahydro-1,8a-dimethyl-7-(1-methylethyl)naphthalene, 9 CI) is thought to be derived from the eudesmane skeleton by migration of the C-10 methyl group to C-5 [16]. Two eremophilanes: nootkatone (1(10),11-eremophiladiene-2-one [4674-50-4]) (**430**) [22,43] and valencene (1(10),11-eremophiladiene (4\(\alpha\),5\(\alpha\),7\(\beta\)) [4630-07-3]) (**431**) [28] are currently reported from _A. annua_. The aristolane sesquiterpenoid, \(\beta\)-gurjunene (1(10)-aristolene [73464-47-8]) (**432**) [34], is the only example of a 6,11-cycloeremophilane from this species.  
\begin{table}
\begin{tabular}{c c c}  & **Table 34**. _Cont._ \\ \end{tabular}
\end{table}
Table 34: _Cont._