Synthesen von Galactose‐Cluster‐haltigen Steroid‐Derivaten

Abstract

Synthesis of Galactose-Cluster-Containing Steroid DerivativesThe synthesis of galactose Clusters that are linked to a Steroid moiety by a peptide-like spacer unit is described. The galactose Cluster is obtained by Koenigs-Knorr glycosylation of TRIS-Gly-Fmoc (2 b) under Helferich conditions. Peptide and ester bonds are formed after activation of carboxylic acids as diphenylthiophene dioxide (TDO) esters. 6a is synthesized in a convergent way by coupling of (Ac 4 Gal) 3 -TRIS-Gly (3e) with cholesteryl TDO succinate (5b). Coupling of (Ac 4 Gal) 3 -TRISGly hydrogen succinate (3f) with Gly-O-Chol (5d) by means of EEDQ yields 6d. Reaction of (Ac 4 Gal) 3 -TRIS-Gly-SUCC-0-TDO (3 g) with 25-hydroxycholesterol leads in a linear sequence to the oxysterol derivative 6f. Selective cleavage of the acetyl groups from galactose units yields the known Compound 6 b and the new derivatives 6e and 6g.