Multi gram-scale synthesis of galactothionolactam and its transformation into a galactonoamidine

We recently proposed to conduct selective glycosylation reactions after in situ activation of a glycosyl donor promoted by a transition metal complex immobilized in a macromolecular matrix. In order to develop this catalytic entity, a feasible multi gram-scale synthesis for 2,3,4,6-tetra-O-benzyl-d-galactothionolactam, its transformation into galactonoamidines with aromatic aglycon, and subsequent debenzylation conditions were developed. The potential for epimerization reactions at C-2 of the glycosidic ring during the transformations from the 2,3,4,6-tetra-O-benzyl-d-galactonolactam into the N-benzyl-2,3,4,6-tetra-O-benzyl-d-galactonoamidines via the 2,3,4,6-tetra-O-benzyl-d-galactothionolactam are discussed and additionally characterized by using density functional theory calculations.