Leaving group based intramolecular glycoside bond formation

Behrendt, Michael E.; Schmidt, Richard R.

doi:10.1016/s0040-4039(00)61687-8

Cited by 24 publications

(9 citation statements)

References 21 publications

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“…Ethyl 2,4,6-Tri-O-benzyl-3-O-[3-(tert-butoxy)-1,3-dioxopropyl]-1-thio-a-d-mannopyranoside (20). A soln.…”

Section: Experimental Partmentioning

confidence: 99%

“…Acetal [1 ± 11] and silylene-acetal linkers [12 ± 16] have been among the first to have been used systematically for this purpose. Furthermore, carbonates [17 ± 19], orthoesters [20], and cobaltcarbonyl complexes of alkynes [21] have also been applied as temporary linkers for this approach. However, thorough investigations of intramolecular glycosylations of this type revealed that also intermolecular processes may be involved during the formation of the O-glycosidic bond [19] [20].…”

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confidence: 99%

“…Furthermore, carbonates [17 ± 19], orthoesters [20], and cobaltcarbonyl complexes of alkynes [21] have also been applied as temporary linkers for this approach. However, thorough investigations of intramolecular glycosylations of this type revealed that also intermolecular processes may be involved during the formation of the O-glycosidic bond [19] [20]. The second strategy for establishing intramolecular glycosylation resembles Ogawas cycloglycosylation [22 ± 24] and makes use of stable persisting tethers between donor and acceptor that are not cleaved during glycosidic-bond formation [25 ± 42].…”

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Untitled

Lemanski

Ziegler

2000

HCA

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A series of prearranged glycosides 5, 17, 23, 28, 37, and 41, having a benzyl-protected 1-thiomannosyl donor linked through its positions 2, 3, 4, and 6 via succinate and malonate tethers, respectively, to positions 2, 3, and 6 of a benzyl glucopyranoside acceptor, were prepared by condensation of the respective mannosyl succinates and malonates with suitably protected benzyl glucopyranosides. The prearranged glycosides were intramolecularly coupled under various conditions to give the corresponding tethered (1 3 4)-linked disaccharides. The yields and anomer ratios of the products of these couplings were interpreted in terms of the thermodynamic stability of the resulting disaccharides. In the case of prearranged glycoside 17, having positions 3 of both the donor and the acceptor linked by a succinate tether, a strong dependence of the diastereoselectivity of the intramolecular glycosylation on the activation procedure was observed. All other cases did not show a significant dependence of the outcome of the anomeric configuration in intramolecular glycosylation on the activation procedure or the solvent.Prearranged glycosides tethered via position 4 of the respective mannosyl residues were prepared as follows. First, a suitably protected mannoside was needed to allow the introduction of the succinyl tether. Thus, phenyl 1-thiomannoside 25 was first prepared by opening of the benzylidene ring [46] of phenyl 2,3-di-O-benzyl-4,6-O-benzylidene-1thio-a-d-mannopyranoside (24) [51] (Scheme 3). Next, succinylation at position 4 afforded monosaccharide 26 (89%), which was again condensed with glucoside 3. The thus-obtained succinyl-tethered glycoside 27 (74%) was converted as described above to compound 28 (78%) and cyclized (see below, Table) to the tethered disaccharides 29. As previously observed for the tethered disaccharides 18, no assignment of the anomer configuration of saccharides 29a and 29b could be made by NMR spectroscopy (C(1) of the mannosyl residue at 100.4 (29a) and 100.8 ppm (28a); corresponding 1 J 175.0 (29a) and 173.7 Hz (29b)). Therefore, disaccharides 29 were each deacylated and benzoylated to give saccharides 30, which now showed characteristic C,H-coupling constants ( 1 J 174.1 Hz (30a) and 156.9 Hz (30b)). For comparison reasons, the Table (see below) also shows the already known results of the cyclization of compound 31, which established the formation of anomer mixtures of tethered disaccharides 32 and 33, respectively, depending on the reaction conditions [41].

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“…Ethyl 2,4,6-Tri-O-benzyl-3-O-[3-(tert-butoxy)-1,3-dioxopropyl]-1-thio-a-d-mannopyranoside (20). A soln.…”

Section: Experimental Partmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Untitled

Lemanski

Ziegler

2000

HCA

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“…In contrast with the above strategies, Schmidt and Behrendt investigated another approach in which the glycosyl acceptor was attached directly to the leaving group [27]. Treatment of 44 with LDA and benzaldehyde resulted in 45 as a 1 : 1 mixture of diastereomers in 90% yield (Scheme 13).…”

Section: Tethering To the Leaving Groupmentioning

confidence: 99%

Intramolecular Glycosidation Reactions

Madsen¹,

Bols²,

Ernst

et al. 2000

Carbohydrates in Chemistry and Biology

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“…Furthermore, the glycosyl acceptor can also be attached to the leaving group of the gly-the anomeric outcome of the cyclisation. For example, it was recently thought that for intramolecular mannosylacosyl donor, either by an orthoester moiety, [14] a carbonate tether, [15] [16] [17] or by the formation of a complex with the tions via prearranged glycosides, a double asymmetric induction may govern the diastereoselectivity of the O-glycoleaving group [18] . However, competition experiments have revealed recently [17] that this approach can also proceed in-side formation [25] .…”

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