Modifications of the orthoester method of glycosylation

Chemical approach for the syntheses of GM4 isomers with sialic acid to non-natural linkage positions on galactose

“…Synthetic route via an orthoester 22 was initially tried to synthesize compound 1. However, the method gave low yield in benzylation.…”

Synthesis and Haemolytic Activity of Randianin Isomers

“…In a similar procedure, peracetyl laminaribiose obtained from 1,2:5,6-di-Oisopropylidene--D-glucopyranose and 3,4,6,-Tri-O-acetyl--D-glucopyranose 1,2-(tert-butyl orthoacetate) [18] was converted to -peracetyl laminaribiose bromide and used for the synthesis of randianin (1) via 8. The con®guration of the anomeric carbons was determined by NMR spectroscopy as described before.…”

“…After addition of 100 mg I 2 , a solution of 430 mg (0.61 mmol) acetobromolaminaribiose in 5 ml dry CHCl 3 was added. (Acetobromolaminaribiose was obtained by bromination [15] of peracetyllaminaribiose which was prepared from diacetone glucose as described [17,18]). This mixture was stirred under Ar for 48 h, ®ltered, and CHCl 3 was evaporated.…”

Glycosylation of a Newly Functionalized Orthoester Derivative

“…In particular, construction of a cyclic carboxonium ion between the C1 and C2 positions is an effective method to obtain the corresponding β-glycosidic linkage of D-sugars, although orthoesters are produced as side products when sterically hindered functional groups are used in glycosyl donors and acceptors [3][4][5][6]. Orthoesters were known to be converted to the corresponding glycosides under acidic conditions, and relatively stable derivatives were employed as glycoside precursors by Kochetkov [7][8][9][10][11] and Kunz [12,13]. We reported the synthesis and reaction of the orthoester 1 (Figure 1), which could be purified by silica gel column chromatography and kept for one month at room temperature [14].…”

“…5.85 (1H, t, J = 9.8 Hz, H-3), 7.23 (2H, m, Ar), 7.39 (25H, m, Ar), 7.61 (2H, m, Ar), 7.74 (4H, m, Ar), 7.85 (4H, m, Ar), 7.93 (6H, m, Ar); 13 C-NMR (100 MHz) δ 46.6 (Fmoc), 65.9 (C-6), 68.4 (C-6'), 69.4 (C-4'), 69.5 (C-4'), 70.2 (C-3'), 70.4 (C-3), 71.6 (C-2), 72.0 (C-2'), 72.8 (C-5'),74.0 (FmocCH 2 ), 78.3 (C-5), 85.9 (C-1'), 101.0 (C-1), 119.9 (Ar), 125.3 (Ar), 125. 4 (12).…”