✦ LIBER ✦
Iodonium ion promoted reactions at the anomeric centre. II An efficient thioglycoside mediated approach toward the formation of 1,2-trans linked glycosides and glycosidic esters
✍ Scribed by G.H. Veeneman; S.H. van Leeuwen; J.H. van Boom
- Publisher
- Elsevier Science
- Year
- 1990
- Tongue
- French
- Weight
- 271 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
N-iodosuccinimide (ND) in the presence of an organic acid was found to be effective for the activation of fully acylated thioglycosides leading to J&trans linked esters. On the other hand, NIS together with a catalytic amount of tri#luoromethanesu&onic acid proved to be very convenient for the rapid, high-yielding and stereoselective (I 2-trans) glycosidation of esterified thioglycosides with glycosyl acceptors.
Recent investigations in thii laboratory revealed* (see Scheme I) that in situ coupling of perbenxylated thioglycosides (e.g. 1, so-called "armed" donor) with partially benxoylated thioglycosides (e.g., 2: so-called "disarmed" acceptor) could be realixed in the presence of the highly chemospecific thiophilic promotor iodonium dicollidine perchlorate (lDCP). It was also established that the IDCP-mediated condensation proceeded with high cr-stereospecificity (e.g., disaccharide 3 was formed in a a/B ratio of 7:l). sehcnr I nno--. moy %,f -J-o.