- 1-azabicyclo[3.3.1]nonan-2-one: Nitrogen versus oxygen protonation
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Protonation of typical unstrained amides and lactams is heavily favored at oxygen. In contrast, protonation of the highly distorted lactam 1-azabicyclo[2.2.2]octan-2-one is heavily favored at nitrogen. What structures occupy "crossover boundaries" where N- and O-protonation are nearly equienergetic Density function theory calculations at the B3LYP/6-31G* level, as well as QCISD(T)/6-31G* calculations, predict that 1-azabicyclo[3.3.1]nonan-2-one favors N-protonation at nitrogen only very slightly (1H and 13C NMR as well as ultraviolet (UV) studies of this lactam, in its combination with sulfuric acid, confirm predominant protonation at nitrogen. Although the calculations very slightly favor the N-protonated chair-chair conformation, experimental spectra clearly support the N-protonated boat-chair. Broadened resonances in the 13C NMR spectrum suggest an exchange phenomenon. Variable-temperature studies of the 13C NMR spectra support dynamic exchange between the major tautomer (N-protonated) and the minor tautomer (O-protonated) in a roughly 4:1 mixture. The findings also support the published prediction that a twisted bridgehead lactam with the nitrogen lone pair (nN) as HOMO will protonate at nitrogen.
- Sliter, Brian,Morgan, Jessica,Greenberg, Arthur
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- Tricycle substituted with azaheterocyclic carboxylic acids
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The present invention relates to novel N-substituted azaheterocyclic compounds of the general formula wherein X, Y, Z, R1, R2 and r are as defined in the detailed part of the present description, or salts thereof, to methods for their preparation, to compositions containing them, and to their use for the clinical treatment of painful, hyperalgesic and/or inflammatory conditions in which C-fibers play a pathophysiological role by eliciting neurogenic pain or inflammation as well as their use for treatment of indications caused by or related to the secretion and circulation of insulin antagonizing peptides, e.g. non-insulin-dependent diabetes mellitus (NIDDM) and ageing-associated obesity.
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