Two conformationally defined analogues of phenylethanolamine, 8-amino-6,7,8,9-tetrahydro-5,8-methano-5H-benzocyclohepten-endo-9-ol (5) and 8-amino-6,7,8,9-tetrahydro-5,8-methano-5H-benzocyclohepten-exo-9-ol (6), have been synthesized. The benzobicyclo[3.2.1]octane skeleton was constructed by an intramolecular cyclization of 3-phenylcyclopentane-1,1-dicarboxylic acid (10). The sodium borohydride reduction of 8-amino-9-oxo-6,7,8,9-tetrahydro-5,8-methano-5H-benzocycloheptene (12) gave the endo alcohol 5. The greater stability of the exo alcohol 6 compared to 5 was confirmed by AM1 calculations. The exo alcohol 6 was obtained from 5 by an N to O acetyl migration. A possible mechanism for this migration in the inversion of the stereochemistry at C-9 is discussed. Structural assignments using 2-D NMR spectra and an NOE difference spectrum are presented.
ASJC Scopus subject areas
- Organic Chemistry