Koenigs-Knorr Synthesis of Galactofuranosides of Estrone, Androstanolone, 11a-Hydroxyprogesterone and Prednisolone

Abstract

Galactofuranosylation has been accomplished with 1-bromo-1-deoxy-2,3,5,6-tetra-O-benzoyl-a-D-galactofuranoside in the presence of cadmium carbonate as promotor. Glycosylation agent has been prepared by bromination of penta-O-benzoyl-ab-D-galactofuranoside with a solution of hydrogen bromide in glacial acetic acid. The precursor of the latter reaction has been produced by benzoylation of D-galactose that had been heated in pyridine while still warm. The following hydroxysteroids have been selected as being representative in terms of configuration, type of hybridization of carbon bearing hydroxyl, position on cyclopentenoperhydrophenantrene nucleus and, implicitly, the degree of shielding: estrone, androstanolone, 11-a-hydroxyprogesterone, prednisolone. The synthesized galactofuranosides have been characterized by 1H and 13C NMR as well as by chromatographic and chemical means.