Study of rotational isomerism of captopril by NMR, infrared and theoretical calculations

• Grant number: 06/06326-1
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: February 01, 2007
• End date: January 31, 2008
• Field of knowledge: Physical Sciences and Mathematics - Chemistry - Organic Chemistry
• Principal Investigator: Roberto Rittner Neto
• Grantee: Silvia Regina Miyagi
• Host Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil

Abstract

The main goal of this project is the investigation of the conformational equilibrium of captopril [1-(D-3-mercapto-2-methylpropionyl)-L-proline] through a methodology, which was well established in our laboratory. This methodology makes use of changes in appropriate coupling constants, due to changes of the solvent and, consequently, on the solution polarity, which correlate with the variation of rotamer populations. Ab initio calculations and Solvation Theory will be used to predict the geometries and energies of the stable rotamers both in the vapour phase as in solution, as well as to obtain the coupling constants in the studied solvents. Another two series of coupling constant values will be obtained: the first by strictly theoretical methods and the other from the NMR spectra. Natural Bond Orbital (NBO) populations will also be obtained for the interpretation of the conformational stability. Infrared spectroscopy will be utilized in the identification of the possible rotamers as well as for a semi-quantitative determination of their population.