Megastigmanes or C13 isonorterpenoids a terpene class of compounds, specially the title compounds are related to sesquiterpenoides but due to C13 skeleton also it is called as norterpenoides. Most of the megastimane compounds have been isolated from the plant source such as Cucumis sativus, Crotalaria zanzibarica, staphylea bumalda, Juniperus communis and Excoecaria cohinchinensis etc. Few reports were showing the megastimane compounds are showing potencial activity against scavenging radical (DPPH) and hepatoprotective activities. The classification of C13 norisoprenoides, are assumed to be apocarotenoides that is formed from the degradation of carotenoides by the action of carotenoides cleavage dioxygenases which have been isolated from various plants. The majority of the evidences for this assumption is the similarly between most megastigmanes and the terminal component of plant carotenoides. Because such compounds are generally not oxygenated at C7 but commonly oxygenated at C9 presumably as a result of the oxidative cleavage of the acyclic portion of caritenoides, the key step in megastigmanes formation has been thought to be transportion of oxygen from C9 to C7. Hence, based on the above information the C9 position and its absolute configuration is very important to get potential activity against various diseases, in this progression a lot of literature reports were showing the importance and absolute configuration at C9 position in megastigmanes or C13 norisoprenoides. In this review, we are reporting the chemistry, absolute configuration and bioactivities of megastigmanes or C13 norisoterpenoides. To our knowledge, this is the first review on megastimanes and its absolute configuration.