Abstract: The stereochemistry of the heterocyclic alcohols(1_4) containing piperidine unit was studied on the basis of the results of molecular mechanics and quantum chemistry calculations. The results showed that there existed the nonclassical orbital superconjugated interactions between the nitrogen atoMAnd oxygen atom which caused the conformations to be more stable when the hydroxylic group lay at axial than at equatorial with respect to the piperidine ring in compound 1 and compound 3. If the axial hydrogen atoms at C₂and C₆positions in the piperidine ring were substituted, or the molecular existed in the polar solutions, this nonclassical orbital superconjugated interactions would be much weak even diminished. In this case, the conformations were more stable when the hydroxylic group at equatorial than at axiaLIn these compounds.

Key words: Heterocyclic alcohols containing piperidine unit, Stereochemistry, Nonclassical orbital superconjugated interactions, Transannular electrostatic interactions