Phenyl galactopyranosides – 13C CPMAS NMR and conformational analysis using genetic algorithm

Abstract Structural analyses of four compounds (phenyl 2,3,4,6-tetra- O -acetyl-β- d -galactopyranoside ( 1 ), phenyl β- d -galactopyranoside ( 2 ), phenyl 2,3,4,6-tetra- O -acetyl-α- d -galactopyranoside ( 3 ) and phenyl α- d -galactopyranoside ( 4 )) have been performed using solid-state 13 C MAS NMR spectroscopy and theoretical methods. Conformational analysis involved grid search and genetic algorithm (GAAGS). Low-energy conformers found by GAAGS were further optimized by DFT and chemical shifts were calculated using GIAO/DFT approach. 13 C CPMAS NMR chemical shift of carbon C2 is indicative of the glycoside torsional angle. Separated or merged resonances of C2 and C6 suggest free rotation of phenyl ring in the solid phase.