Conformationally Constrained Nicotines. 1-Pyridinyl-7-azabicyclo[2.2.1]heptane and 1-Pyridinyl-8-azabicyclo[3.2.1]octane Analogues
摘要:
Conformationally constrained bicycle analogues of natural (-)-nicotine and unnatural (+)-nicotine have been synthesized from D- and L-glutamic acid, respectively. Regioselective addition of 3-lithiopyridine to the gamma-carbonyl of a protected glutamate was followed by intramolecular imine formation and stereospecific catalytic hydrogenation of the resultant pyrroline to give cis-5-pyridinylproline. A sequence of transformations to convert the ester to bromide was followed by the key intramolecular anionic cyclization at the benzylic position to form the 1-pyridinyl-7-azabicyclo[2.2.1]heptane analogue. Alternatively, homologation of the ester of cis-5-pyridinylproline and conversion to bromide allowed cyclization to the 1-pyridinyl-7-azabicyclo[3.2.1]octane analogues.
Conformationally Constrained Nicotines. 1-Pyridinyl-7-azabicyclo[2.2.1]heptane and 1-Pyridinyl-8-azabicyclo[3.2.1]octane Analogues
摘要:
Conformationally constrained bicycle analogues of natural (-)-nicotine and unnatural (+)-nicotine have been synthesized from D- and L-glutamic acid, respectively. Regioselective addition of 3-lithiopyridine to the gamma-carbonyl of a protected glutamate was followed by intramolecular imine formation and stereospecific catalytic hydrogenation of the resultant pyrroline to give cis-5-pyridinylproline. A sequence of transformations to convert the ester to bromide was followed by the key intramolecular anionic cyclization at the benzylic position to form the 1-pyridinyl-7-azabicyclo[2.2.1]heptane analogue. Alternatively, homologation of the ester of cis-5-pyridinylproline and conversion to bromide allowed cyclization to the 1-pyridinyl-7-azabicyclo[3.2.1]octane analogues.
Conformationally constrained bicycle analogues of natural (-)-nicotine and unnatural (+)-nicotine have been synthesized from D- and L-glutamic acid, respectively. Regioselective addition of 3-lithiopyridine to the gamma-carbonyl of a protected glutamate was followed by intramolecular imine formation and stereospecific catalytic hydrogenation of the resultant pyrroline to give cis-5-pyridinylproline. A sequence of transformations to convert the ester to bromide was followed by the key intramolecular anionic cyclization at the benzylic position to form the 1-pyridinyl-7-azabicyclo[2.2.1]heptane analogue. Alternatively, homologation of the ester of cis-5-pyridinylproline and conversion to bromide allowed cyclization to the 1-pyridinyl-7-azabicyclo[3.2.1]octane analogues.