A facile, one-step procedure for the conversion of 2-(trimethylsilyl) ethyl glycosides to their glycosyl chlorides

NRC publication: Ye

Observations on chemical and enzymatic approaches to α-2,3-sialylated octyl β-lactoside

A comparison of chemical and chemo-enzymatic syntheses of alpha-2,3-sialylated octyl lactoside is reported. the chemical approach, starting from lactose and sialic acid, required 14 steps and proceeded in 5% overall yield; poor a-selectivity in the sialylation step necessitated a difficult and low yielding separation of anomers. A chemoenzymatic approach, employing recombinant Trypanosoma cruzi trans-sialidase to effect the key sialylation reaction, required 10 steps and gave a similar overall yield. Whereas the chemo-enzymatic synthesis required only three chromatographic purification steps overall, the chemical synthesis required at least nine. (C) 2002 Elsevier B.V. All rights reserved.Univ St Andrews, Sch Chem, St Andrews KY16 9ST, Fife, ScotlandUniv St Andrews, Ctr Biomol Sci, St Andrews KY16 9ST, Fife, ScotlandEscola Paulista Med, Disciplina Biol Celular, BR-04023062 São Paulo, BrazilEscola Paulista Med, Disciplina Biol Celular, BR-04023062 São Paulo, BrazilWeb of Scienc

Streamlined Synthesis of Per-O-acetylated Sugars, Glycosyl Iodides, or Thioglycosides from Unprotected Reducing Sugars1

Solvent-free per-O-acetylation of sugars with stoichiometric acetic anhydride and catalytic iodine proceeds in high yield (90-99%) to give exclusively pyranose products as anomeric mixtures. Without workup, subsequent anomeric substitution employing iodine in the presence of hexamethyldisilane (i.e., TMS-I generated in situ) gives the corresponding glycosyl iodides in 75-95% isolated yield. Alternatively, and without workup, further treatment with dimethyl disulfide or thiol (ethanethiol or thiocresol) gives anomerically pure thioglycosides in more than 75% overall yield