Epibatidine bioactive conformation

FIGURE 17.8 The reactions of different reagents R1-R4 to a common substrate produce different skeletons.  

CHAPTER 17 Conformational Restriction and/or Steric Hindrance in Medicinal Chemistry 

FIGURE 17.9 Similar substrates with different appendages (cr-elements) 6-8 produces a diversity of skeletons 9-11 with a unique set of reagent.  

The former were obtained by a methylen-oxo bridge between the two heterocycles and the second by linking the basic nitrogen to the pyridine ring. If the two compounds syn-2 and anti-2 were devoid of affinity for the nAChR, syn-2 with the shorter N-N distance retain some affinity althongh modest in respect to EPI = 136 nM). The study 

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