Humulene Wagner-Meerwein rearrangement

A number of biomimetic syntheses have included Wagner-Meerwein rearrangements. A chemical conversion of humulene (48) to sterpurene (50) involved an interesting series of Wagner-Meerwein rearrangements (see Scheme 19).- - Humulene (48) was converted to the cyclooctenol (51) and thence to the bromide (52) via the protoilludyl cation (49). Treatment of (52) with silver acetate in acetic acid gave racemic sterpurene (50). In contrast the epimeric bromide (53) gave (54). 

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