An improved synthesis of 4-azido-4-deoxy- and 4-amino-4-deoxy-α,α-trehalose and their epimers

A highly efficient and convergent synthesis of a hexasaccharide, a dimer of the repeating unit of the antigen O2 polysaccharide of Stenotrophomonas maltophilia

“…Thus, the glycoside acceptor 1, allyl 2,3,6-tri-O-benzoyl-a-D-mannopyranoside, was obtained from allyl a-Dmannopyranoside [3] through selective tribenzoylation with benzoyl chloride in pyridine under the conditions designated for selective benzoylation of trehalose [4] (Scheme 1). The 1 H NMR of 1 gave H-4 as an upfield triplet (l 4.3 ppm), a clear indication of a free OH hydroxyl.…”

“…For the synthesis of disaccharide 6, Scheme 1. an orthoester intermediate was used. Treatment of 'acetobromorhamnose' with MeOH in the presence of 2,4-lutidine/ t Bu 4 NBr instead of sym-collidine/ t Bu 4 NBr [5] gave orthoester 2 in high yield. Deacetylation of 2, followed by benzoylation, gave orthoester 3 in quantitative yield.…”

“…60 (dd, 1 H, J 2%,3% 3.2 Hz, J 3%,4% 9.8 Hz, H-3%), 5. 45 (d, 1 H, J 1,2 1.9 Hz, H-1 (8).-Trichloroacetonitrile (Cl 3 CCN, 0.11 mL, 3 equiv) and 1,8-diazabicyclo [5,4,0]undec-7-ene (DBU, 14 mL, 0.25 equiv) were added to a solution of 7 (310 mg, 0.35 mmol) in anhyd CH 2 Cl 2 (10 mL) and the mixture was stirred at 0°C for 1 h, at the end of which time TLC showed the starting material had disappeared. The solvents were evaporated and flash chromatography (1:1 EtOAc-petroleum ether) of the residue gave the disaccharide donor 8 (300 mg, 0.29 mmol, 83%), which was used directly in the glycosylation reaction; 1 Allyl 4-O-benzoyl-h-L-rhamnopyranoside (11).…”

“…Subsequent treatment with trichloroacetonitrile (Cl 3 CCN, 3 equiv) and 1,8-diazabicyclo [5,4,0]undec-7-ene (DBU, 0.25 equiv) at 0°C in anhyd CH 2 Cl 2 gave, after flash chromatography, the trichloroacetimidate donor 12 (595 mg, overall yield 72% for two steps), which was used directly in the glycosylation reaction [8]. A mixture of the donor 12 (595 mg, 1.19 mmol) and the acceptor 1 (535 mg, 1.0 mmol) in anhyd CH 2 Cl 2 (20 mL) containing 4 Å activated molecular sieves (1 g) was stirred under N 2 for 1 h at rt and then cooled to − 40°C.…”

Facile Synthesis of a Branched Trisaccharide–The Repeating Unit of Antigen O2 Polymer using Orthoester Formation - Rearrangement Strategy

“…Di-0-acetyl-l,2-0-methoxyethylidene-p-L-rhamnopyranose(3). room temperature, and MeOH (anhydrous, 0.5 mL, 12 mmol) was added.…”