Synthesis of 3′- and 4′-deoxyfluorolactose and its Me₃SiCH₂CH₂ and ceramide derivatives

Abstract

(2-Trimethylsily)ethyl (Me₃SiCH₂CH₂)3′- and 4′-deoxyfluorolactosides (1 and 3) were synthesized by glycosylation of Me₃SiCH₂CH₂ 2,3,6-tri-O-benzyl-β-d-glucopyranoside with 2,4,6-tri-O-acetyl-3-deoxy-3-fluoro-β-d- galactopyranosyl bromide and 2,3,6-tri-O-benzyl-4-deoxy-4-fluoro-β-d-galactopyranosyl bromide. Anomeric deblocking of the fully acetyled Me₃SiCH₂CH₂ glycosides (12 and 13) gave the corresponding hemiacetals 14 and 15. Removal of the acetyl groups gave 3′- and 4′-deoxyfluorolactose (2 and 4). The deoxyfluorolactosylceramides 5 and 6 were synthesized via boron trifluoride etherate- or silver triflate-activation of the trichloroacetimidates prepared from 14 and 15. Silver triflate-mediated glycosylations showed lower reaction rates, and fewer byproducts were formed.