New approaches to analogs of α-linked galactosylceramides based on functionalized serinol

Resumo

New derivatives of serinol, 3-[4-(2-chloroethoxy)benzyloxy]-2-phthalimidopropan-1-ol and 3-[4-(2-azidoethoxy)phenoxy]-2-phthalimidopropan-1-ol, were synthesized and tested as glycosyl acceptors in stereoselective 1,2-cis-galactosylation in the benzyl-free synthesis of analogs of α-linked galactosylceramides. It was found that NIS/AgOTf-promoted glycosylation of 3-[4-(2-chloroethoxy)benzyloxy]-2-phthalimidopropan-1-ol with ethyl 4,6-O-(di-tert-butylsilylene)-1-thio-β-D-galactoside resulted in both the expected α-linked diastereomeric glycosides and the product of iodination of the benzyl group of the aglycon. This process was avoided by using the corresponding galactosyl imidate under Et₃SiOTf promotion to give exclusively α-linked diastereometic serinol glycosides.