Physostigmine and related compounds

In dilute acid solution, the Ph—N-8—C-8a—N-1 system present in physostigmine and related compounds is protonated on N-1 (9). The results of investigations have now been published (40) in w hich it has been shown that as the concentration of the acid is increased, cleavage of the C-8a—N-1 bond in these compounds occurs with formation of the corresponding 3//-indolium cations (XX) as shown. Evidence for... 

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