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.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.