Dammarenyl cation

Comparison of the amino acid sequences of OSCs that generate sterols and triterpenoids reveals a number of residues in addition to the DCTAE and QW motifs that are highly conserved in all classes. These residues may be required to open up the epoxide ring of 2,3-oxidosqualene, a catalytic step that is common to all of these enzymes [46]. Amino acid residues that are conserved exclusively in sterol OSCs or in triterpenoid OSCs maybe required for formation of the pro-tosteryl or dammarenyl cations, respectively. 

The dammarenyl cation (21) represents the first branch point from which numerous mechanistic pathways of triterpene synthesis diverge. A detailed and interesting study of molecular modelling and conformational analysis indicates that the formation and... 

Through a series of cyclizations, squalene oxide (C30) affords lanosterol in animals and fungi and cycloartenol in plants (Fig. 19). In both instances, the intermediate is a protosteryl cation that can also undergo a series of Wagner-Meerwein rearrangements to afford the cytotoxic cucurbitacins of melons and cucumbers. Squalene oxide in a chair-chair-chair-boat conformation yields the dammarenyl cation, a parent of numerous triterpene skeleta (e.g., lupane, oleanane, ursane, and taraxerane) contained in the saponins found in many foodstuffs, in soaps, and in several... 

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