186038-68-6Relevant academic research and scientific papers
Observations on the activation of methyl thioglycosides by iodine and its interhalogen compounds
Kartha, K.P. Ravindranathan,Cura, Peter,Aloui, Mahmoud,Readman, S. Kristy,Rutherford, Trevor J.,Field, Robert A.
, p. 581 - 593 (2000)
Treatment of 'armed' methyl thiogalactosides with iodine in the absence of an acceptor alcohol results in thioglycoside epimerisation, whereas there is no effect on the corresponding 'disarmed' methyl thioglycosides. In contrast, iodine-hexamethyldisilane (which generates iodotrimethylsilane in situ) brings about epimerisation of 'disarmed' thioglycosides, ultimately giving rise to the corresponding α-glycosyl iodides on extended exposure. Cross-over experiments show the former iodine-promoted epimerisation process to be intermolecular, whereas the latter iodine-hexamethyldisilane-promoted epimerisation is intramolecular. Treatment of the same methyl thiogalactosides with iodine monobromide gives rise to the thermodynamically favoured α-glycosyl bromides, whereas reaction with iodine monochloride initially gives the kinetic β-glycosyl chlorides, which slowly epimerise to the thermodynamic α-linked products. Differences in the outcome of thioglycoside activation by I-I, I-Br and I-Cl suggest there may be scope for influencing the stereochemical course of thioglycoside-based glycosylation reactions through careful choice of promoter. Copyright (C) 2000 Elsevier Science Ltd.
Convenient syntheses of 2,3,4,6-tetra-O-alkylated D-glucose and D-galactose
Kaesbeck, Ludwig,Kessler, Horst
, p. 169 - 173 (2007/10/03)
Convenient syntheses of the 2,3,4,6-tetra-O-benzylated and -allylated D-glucopyranoses 1 and 2 and the corresponding D-galactopyranoses 3 and 4 are described. The D-glucose derivatives 1 and 2 were obtained from inexpensive sucrose by peralkylation and subsequent acid hydrolysis. In this reaction sequence an alkylated D-fructofuranosyl cation is generated which was trapped by different nucleophiles to afford 4-benzyloxymethylenefurfural (8) and the alkylated D-fructosides 7, 8 and 10. On the other hand 2,3,4,6-tetra-O-benzyl-D-galactose 3 was synthesized by oxidative cleavage of ethyl 2,3,4,6-tetra-O-benzyl-1-thio-α,β-D-galactopyranoside (11) with aqueous N-bromosuccinimide. The alternative route for the preparation of 2,3,4,6-tetra-O-allyl-D-glucopyranoside (2) via p-methoxybenzyl β-D-glucoside is less attractive. However, this route was used for the synthesis of 2,3,4,6-tetra-O-allyl-D-galactose (4). VCH Verlagsgesellschaft mbH, 1997.
