Neber rearrangement natural product synthesis

The Neber rearrangement has for example found application in natural product synthesis. 

Despite the powerful potential of the Neber rearrangement, it has been scarcely utilized in the total synthesis of complex natural products. The earliest such application was in Woodward s total synthesis of lysergic acid. Although not utilized in the successful route to this alkaloid, an early approach to the a-aminoketone (24) exploited the Neber rearrangement on compound 22. Preparation of the oxime (23) followed by rearrangement provided the amine hydrochloride 24 in good yield however, this compound was unstable as a free base and could not be processed further en route to lysergic acid. 

Perhaps the most complex natural product total synthesis that features a Neber rearrangement is Stoltz s total synthesis of dragmacidin Oxime formation and tosylation on 25 efficiently provided 26. Neber... 

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