## 2 The Phytochemistry of _Artemisia annua_ L. (Qinghao)
### Sesquiterpenenoids
#### 2.6.3.4 Guaianes  
Guaianes (Table 39) are bicyclic sesquiterpenes which contain fused 5- and 7-membered rings. Guaianes are often found together with eudesmanes (which contain two fused 6-membered rings - see Table 34) and may be derived by an alternative cyclization of the same germacrane precursor which gives rise to eudesmanes.  
Aromadendrane sesquiterpenes (Table 40) are 6,11-cycloguaianes, in which an additional cyclopropyl ring has been formed by further cyclization of a guaiane precursor. The unusual metabolite, nortaylorione (15-_nor_-1,10-_seco_-1(5)-aromadendrene-4,10-dione [163128-16-3]) [**519**] [257], might be viewed as the product of oxidative rearrangements of such an aromadendrane precursor. The cubebane sesquiterpenoids (octahydro-3,7-dimethyl-4-(1-methylethyl)-_IH_-cyclopenta[1,3]-cyclopropa-[1,2]-benzene, 9 CI): \(\alpha\)-cubehene (3-cubehene [17699-14-8]) (**520**) [51] and \(\beta\)-cubehene [4(15)-cubehene [13744-15-5], (**521**)] [19,38,51,66], are also representatives of guaianes which have undergone a further cyclization, with the cyclopropyl ring now being formed between positions 1- and 6-. \(\alpha\)-Guaiane (**506**) is the most abundant guaiane sesquiterpene in _A. annua_[22], whilst spathulenol (**515**) is the most common aromadendrane [41] (both can reach levels up to 5% of the essential oil).  
\begin{table}
\begin{tabular}{|c|c|c|c|} \hline
**Name** & **Alternative Name(s)** & **CAS Number** & **References** \\ \hline \(\alpha\)-Guaiene (**506**) & 1(5),11-Guaiadiene & [3691-12-1] & [28, 36] \\ \hline \(\beta\)-Guaiene (**507**) & 1(5),7(11)-Guaiadiene & [88-84-6] & [32] \\ \hline \(\gamma\)-Gurjunene (**508**) & 5,11-Guaiadiene & [22567-17-5] & [31, 34] \\ Guaiazulene (**509**) & 2,4-Dimethyl-7-(1-methylethyl)azulene & [492-45-5] & [24] \\ \hline \end{tabular}
\end{table}
Table 39: Guaiane sesquiterpenoids (Decahydro-1,4-dimethyl-7-(1-methylethyl)azulene, 9 CI).  
\begin{table}
\begin{tabular}{|l|l|l|l|} \hline
**Name** & **Alternative Name(s)** & **CAS Number** & **References** \\ \hline \(a\)-Aromadendrene (**510**) & _allo-_Aromadendrene & [25246-27-9] & [23, 40, 43] \\  & 10(14)-Aromadendrene & [14682-34-9] & \\ \hline \(a\)-Gurjunene (**511**) & 4-Aromadendrene & [489-40-7] & [48] \\ \hline Globulol (**512**) & (1a,4a,5b,6a,7a,10a)-10-Aromadendranol & [489-41-8] & [19, 28, 34] \\ \hline _epi-_Globulol (**513**) & _IH-_Cycloprop(e)_|zalue-4-ol, decahydro-1,1,4,7- & [88728-58-9] & [34] \\  & tetramethyl:, (1a,4S,4 aR,7R,7 aS,7 bS)- & & \\ \hline Ledol (**514**) & 10-Aromadendron (18,4a,5b,6b,7b,10a) & [577-27-5] & [28] \\ \hline (-)-Spathulenol (**515**) & 10(14)-Aromadendren-4-ol & [77171-55-2] & [19, 27, 31, 32, 41, 43, 45] \\ \hline Cycloprop[7,8],8 azuleno[3a,4 -b]oxviene, decahydro- 1,4a,7,7-tetramethyl-, (1R,6 aR,7 aR,7R)- (**516**) & & \\ \hline Aromadendrene epoxide & Isoamodendrene epoxide & [85710-39-0] & [23, 34] \\ \hline (**517**) & 10(14)-Aromadendrene 10b,14-epoxide & [499134-59-7] & [45] \\ \hline Cyclocorlorenone (**518**) & 4-Aromadendren-3-one & [489-45-2] & [45] \\ \hline \end{tabular}
\end{table}
Table 40: Aromadendrane Sesquiterpenoids (Decahydro-1,1,4,7-tetramethyl-_IH_-cycloprop[e]azulene. 9 CI).