Experimental and theoretical evidences of conformational flexibility of C-glycosides. NMR analysis and molecular mechanics calculations of C-lactose and its O-analogue

Abstract NMR data (NOEs and coupling constants) and MM3 ∗ molecular mechanics calculations have allowed to demonstrate that the conformational behaviour of C-lactose is different of its O-analogue. The glycosidic linkages, particularly the C-aglyconic bond, present a high degree of flexibility and, therefore, the conformational entropy of C-lactose is higher than that of its O-counterpart.