Cucurbitane

Mogroside V (2) is a cucurbitane-type triterpenoid glycoside isolated from the fhiits of Siraitia grosvenorii (Swingle) C. Jeffrey... 

The first successful transformation of a lanostane into a cucurbitane by a cationic process has been reported. On exposure to acid 3/3-acetoxy-9a-hydroxy-11-keto-5a-lanostane afforded two rearranged products (51) and (52) with a cucurbitane... 

An elegant correlation of the lanostane and cucurbitane series has been reported by Barton and his colleagues. Cucurbitacin A (46) was transformed into the cyclopropane derivative (47) by treatment of the tosylate (48) with sodium borohydride. The cyclopropane ring of the tetrahydro-compound (49) was opened by an anionic process which involved protonation of the incipient... 

Thus, once the appropriate orientation within the corresponding enzyme occurs, steroids, cucurbitacins, or other triterpenes may be formed. In the case of cucurbitacins, the squalene epoxide adopts a chair-boat-chair conformation, and the cyclization leads to a protostane cation, which is the immediate precursor of the cucurbitanes through a series of 1,2-proton and methyl group shifts, Fig. (4) [40]. 

From the anti-inflammatory, antipyretic, analgesic, and antioxidant extract of Kageneckia oblonga, Delporte et al. [13] isolated two cucurbitacins which were assayed as potential antioxidants and also as inhibitors of enzymes implicated in inflammatory reactions. Isolated compounds, 23,24-dihydrocucurbitacin F and 3P-( 3-D-glucosyloxy)-16a,23a-epoxy-cucurbitan-5,24-diene-ll-one, Fig. (11), inhibited the production of superoxide anion as well as elastase release in stimulated human neutrophils. In addition, the compounds inhibited both nitrite and... 

---