1993
DOI: 10.1016/0008-6215(93)80061-i
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Synthesis of the laminara-oligosaccharide methyl β-glycosides of dp 3–8

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Cited by 66 publications
(40 citation statements)
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“…Glycosylation between acceptor 15 and donor 17 using Niodosuccinimide and H 2 SO 4 -silica afforded the disaccharide 18 in 87% yield. But at this stage selective cleavage of the chloroacetyl group with thiourea in methanol-CH 2 Cl 2 (2:3) mixture in the presence of 2,4,6-collidine [26] failed to produce the desired disaccharide acceptor 19. Even after 24 h reflux with 15-fold excess of thiourea only negligible product was evident by TLC and the resulted product was impossible to purify and characterize (Schemes 4, 5).…”
Section: Resultsmentioning
confidence: 91%
“…Glycosylation between acceptor 15 and donor 17 using Niodosuccinimide and H 2 SO 4 -silica afforded the disaccharide 18 in 87% yield. But at this stage selective cleavage of the chloroacetyl group with thiourea in methanol-CH 2 Cl 2 (2:3) mixture in the presence of 2,4,6-collidine [26] failed to produce the desired disaccharide acceptor 19. Even after 24 h reflux with 15-fold excess of thiourea only negligible product was evident by TLC and the resulted product was impossible to purify and characterize (Schemes 4, 5).…”
Section: Resultsmentioning
confidence: 91%
“…While acetyl groups at O-2 on the donor species are expected to stabilize intermediate oxonium, to induce nucleophilic attack on the opposite site and consequently to favor 1,2-trans couplings, these desired results could not be easily attained using glucopyranosyl acceptors characterized by a free 3-OH and acyl groups to protect other hydroxyl functions [15]. However this difficulty could be overcome by using acceptors bearing a 4,6-benzylidene group [16,17]. Nevertheless, we thought that such elaborated compounds could not be suitable for a pre-industrial process because they require too many syntheses and purification steps for molecule having non-pharmaceutical uses.…”
Section: Resultsmentioning
confidence: 99%
“…In this case, an equimolar ratio of cupper(II) triflate was needed to isolate a 4.9/1 mixture of 6b/8b (entry 13). Nevertheless, the best compromise between yield and selectivity was observed for a catalysis with tin(II) triflate (entry 15) and not with the silver salt (entries 16,17).…”
Section: Glycosylation With Thioglycosidesmentioning
confidence: 99%
“…The previous studies 13 indicated that in (1!3)-glucosylation the glycosyl bond originally present in either donor or acceptor controlled the stereoselectivity of the forthcoming bond, that is, the newly formed glycosidic linkage had the opposite anomeric configuration of that of either the donor or acceptor. In addition, some reports 14,15 revealed that with 4, 6-O-benzylidenated glucose derivatives as either donor or acceptor, b-linked oligosaccharides are readily obtained. Thus, in the present research, the benzylidenated glucose derivatives were applied as the key intermediates.…”
mentioning
confidence: 98%