Synthesis of New Hexosaminyl D‐ and L‐chiro‐Inositols Related to Putative Insulin Mediators.

Cid, M. B.; Bonilla, Julia B.; Alfonso, Francisco; Martín‐Lomas, Manuel

doi:10.1002/chin.200403195

Cited by 1 publication

(4 citation statements)

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“…That could be the case of the higher ratio of glycosylation of hydroxyl groups at C3 position even being the most hindered one, compared to OH-2 in α-altrose diol acceptor derivatives described by Fraser-Reid et al [66]. This fact could also explain the glycosylation tendency of the axial hydroxyl group at C1 versus C2 in D-chiro-inositol 1,2-syn diol acceptors [54].…”

Section: Superarmed Glycosyl Donors In Glycosylation Reactionsmentioning

confidence: 91%

“…2) 145 pseudodisaccharides in 67 % combined yield (Fig. 5.36) 148 compounds in 48 % overall yield [54]. The regioselectivity was poorer but followed the same trend in the glycosylation with the less reactive 3,4,6-tri-Oacetyl-2-azido-2-deoxy-D-glycopyranosyl trichloroacetimidate 149 which afforded a 2:1 mixture of the α(1 !…”

Section: Superarmed Glycosyl Donors In Glycosylation Reactionsmentioning

confidence: 95%

“…In the course of their work on the synthesis of inositolphosphoglycans (IPGs) as potential mediators in the insulin signaling process, Martin-Lomas et al [52][53][54][55][56][57][58] have extensively studied the glycosylation reactions of myo-inositol and D-and L-chiro-inositol derivatives (Fig. 5.34) with different glycosyl donors, in particular 2-azido-2-deoxy-glycopyranosyl trichloroacetimidates.…”

Section: Regio-and Stereoselectivity In Glycosylationmentioning

confidence: 99%

“…Thus, a glycal which serves as glycosyl acceptor (54) shall have one free hydroxyl group that will be glycosidically linked to a glycosyl donor 53 and all the other hydroxyl groups acylated. For example, 53 (3,4,6-tri-O-benzyl-D-arabino-glycal) which serves as glycosyl donor has all of its hydroxyl groups benzylated, since the electron-donating C3 alkoxy group enhances the nucleophilicity of the C1-C2 double bond toward the iodonium cation, whereas in the 3,6-di-O-benzoyl-D-arabino-glycal 54 that serves as a glycosyl acceptor, the electron-withdrawing C3 acyl group deactivates (disarms) the nucleophilicity of the C1-C2 double bond toward electrophiles such as the iodonium cation.…”

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confidence: 99%

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Armed-Disarmed Concept in the Synthesis of Glycosidic Bond

Miljković

2013

Electrostatic and Stereoelectronic Effects in Carbohydrate Chemistry

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-Reid et al. reported [1] that n-pentenyl glycosides undergo chemospecific cleavage 1 ! 2 ! 3, with N-bromosuccinimide under conditions that leave a wide variety of other protecting groups unaffected ( Fig. 5.1).According to the proposed mechanism ( Fig. 5.1), the addition of water to the reaction mixture will lead to hydrolysis but the addition of alcohol or another sugar having a free hydroxyl group will lead to the formation of glycoside or a disaccharide. In the course of these studies, Fraser-Reid et al. [1] observed that sugar molecules having an acyloxy group at the C2 carbon (6 in Fig. 5.2) hydrolyzed much more slowly than if they had an alkoxy group (7 in Fig. 5.2). This observation suggested that the n-pentenyl glycoside could be made more or less reactive (it could be armed or disarmed) by the type of protecting group placed on the C2 oxygen.The ability of the C2 acyloxy group to disarm the n-pentenyl glycoside was rationalized as shown in Fig. 5.3. Thus, it can be assumed that the cyclic halonium ions 8 and 9 are formed reversibly [2] and that the electron density on the glycosidic oxygen is depleted in 2-O-acyl derivatives so that nucleophilic attack of this oxygen on the halonium ion is less favored than in the 2-O-alkyl counterpart 9. The reason for this is that the electron-withdrawing group at the C2 carbon makes the C2 carbon slightly positively charged so that the formation of another positive charge at the C1 carbon is not a favorable process [there cannot exist two positive charges on two neighboring carbons (C1 and C2) (Fig. 5.3).].Consequently, the armed glycosyl donors react with electrophiles faster than the disarmed ones, and therefore in a solution containing both an armed and disarmed glycosyl donor molecules, whereby disarmed glycosyl donor molecules have one free hydroxyl group, the reaction with an electrophile will result in crosscoupling and not self-coupling, i.e., an armed glycosyl donor will react with the disarmed one, whereas a disarmed donor will not react with itself [3] as illustrated in Fig. 5.5. The promoters for the activation of n-pentenyl group [4,5] are iodonium dicollidine perchlorate (IDCP) and N-iodosuccinimide/triethylsilyl triflate (NIS/Et 3 SiOTf).M. Miljkovic, Electrostatic and Stereoelectronic Effects in Carbohydrate Chemistry,

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Section: Superarmed Glycosyl Donors In Glycosylation Reactionsmentioning

confidence: 91%

Section: Superarmed Glycosyl Donors In Glycosylation Reactionsmentioning

confidence: 95%