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PM3 Conformational analysis of the (3S,5R,6R) acetylamidopenicillanic acid.1.Geometric properties

Domenii publicaţii > Chimie + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: M.Schulz,M.Mracec,E.Sisu,L.Kurunczi,M.Mracec

Editorial: Rev. Roum. Chim., 53(9), p.847-858 , 2008.


A conformational analysis with the PM3 semiempirical MO method was performed for the (3S,5R,6R)-6-
acetylamidopenicillanic acid. Because the N atom of the exocyclic amidic group is pyramidalized by the PM3 method,
a larger number of conformers (47) than the number of theoretically possible conformers have been obtained. The
conformer that fit the best with the experimental geometry was not the lowest energy conformer, but the fourth
conformer in the energy ascending order. The difference between the lowest energy and highest energy conformer is
11.36 kcal/mol. The calculated average values of various bond lengths, bond angles and dihedrals helped to observe
some regularities in the conformers’ geometries that otherwise could not be observed. The conformers could be divided
in three distinct classes of puckering of the thiazolidinic ring. Ring puckering is not influenced by the rotation of the
carboxylic group.

Cuvinte cheie: analiza conformationala,PM3. // conformational analysis,PM3,(3S,5R,6R)-6-acetylamidopenicillanic acid