Conjugates of polyhedral boron compounds with carbohydrates 7. Hydrolytic stability of closo-ortho-carborane glycoconjugates containing from one to three β-lactosylamine and β-d-galactopyranosylamine residues; estimation of their galectin-binding efficiency with galectin RCA120

Abstract

The galectin-binding efficiency (Ricinus communis agglutinin, RCA) and the degree of deboronation at 37 °C of glycoconjugates of ortho-carboranylacetic acid containing from one to three β-lactosylamine or β-d-galactopyranosylamine residues were estimated; the glycoconjugates are potential agents for boron neutron capture therapy of cancer. Over a period of 24 h, up to ∼15% of glycoconjugates underwent deboronation to give glycoconjugates of nido-ortho-carborane. With Lac-β-NH(COCH2NH)2COCH2-o-CCHB10H10 as an example, it was demonstrated that the deboronation occurs at both 60 and 5 °C. Glycoconjugates with an O-linked β-galactose as a fragment of lactosylamine bind to galectin RCA120 much more efficiently (up to ∼40 times) than do the corresponding glycoconjugates with a N-linked β-galactose residue. The glycoconjugates containing one β-lactosylamine residue bind to galectin RCA approximately two times less efficiently than does lactose; however, introduction of the second and third β-lactosylamine residues into the glycoconjugate increases the binding efficiency by a factor of five to seven due to the cluster effect.