Regioselectivity of glycosylation reactions of galactose acceptors: an experimental and theoretical study

• Enrique A. Del Vigo,
• Carlos A. Stortz and
• Carla Marino

Beilstein J. Org. Chem. 2019, 15, 2982–2989, doi:10.3762/bjoc.15.294

• described. Glycosylations were performed in CH2Cl2 and TMSOTf catalysis (Scheme 2). Galactofuranosyl iodide 5 was obtained by the treatment of per-O-TBS-β-ᴅ-Galf with a stoichiometric amount of TMSI, and glycosylated in situ by adding the acceptor in the presence of EtN(iPr)2 as acid scavenger (Scheme 3

• % CF3COOH, CH2Cl2, 0 ºC, 15 min; g) BnBr, NaH, THF, rt, 16 h; h) BzCl, pyridine, CH2Cl2, rt, 12 h; i) AcOH/H2O, 4:1, v/v, 65 ºC, 6 h. Glycosylation of D-Galp acceptors 1α/β and 2α/β using trichloroacetimidate donors 3 and 4. Glycosylation of acceptors 1α/β using galactofuranosyl iodide 5 as donor. Ratios

Expedient synthesis of 1,6-anhydro-α-D-galactofuranose, a useful intermediate for glycobiological tools

• Luciana Baldoni and
• Carla Marino

Beilstein J. Org. Chem. 2014, 10, 1651–1656, doi:10.3762/bjoc.10.172

• three-step procedure for the synthesis of 1,6-anhydro-α-D-galactofuranose is described. The key step involves the formation of the galactofuranosyl iodide by treatment of per-O-TBS-D-Galf with TMSI, the selective 6-O-desilylation by an excess of TMSI, and the simultaneous nucleophilic attack of the 6

• -hydroxy group on the anomeric carbon, with the iodide as a good leaving group. This compound is a good precursor for building blocks for the construction of 1→6 linkages. Keywords: 1,6-anhydro-α-D-Galf; galactofuranosyl iodide; galactofuranosyl precursor; per-tert-butyldimethylsilyl-β-D-galactofuranose

• glycosylation via the in situ generation of galactofuranosyl iodide 10 (Scheme 2) [32][33][34][35]. Galactofuranosyl iodides were not previously described, and 10 proved to be useful for the synthesis of several D-Galf-containing molecules (Scheme 2) [32]. The reported procedure consisted in the treatment of

Synthesis of a derivative of α-D-Glcp(1->2)-D-Galf suitable for further glycosylation and of α-D-Glcp(1->2)-D-Gal, a disaccharide fragment obtained from varianose

• Carla Marino,
• Carlos Lima,
• Karina Mariño and
• Rosa M. de Lederkremer

Beilstein J. Org. Chem. 2012, 8, 2142–2148, doi:10.3762/bjoc.8.241

• oligosaccharide constituents of pathogenic microorganisms has been achieved [10]. The isopropylidene derivative 4 [23] has been regioselectively glycosylated at HO-2 by the galactofuranosyl iodide method, affording the β-(1→2) linkage with complete regioselectivity [24]. Derivative 4 was also used for the