K. Ullah et al.
Carbohydrate Research 501 (2021) 108257
Scheme 3. Proposed mechanism for the magnesium-mediated isomerization reaction.
(HRMS) were performed by Agilent apparatus on an Electron Spray
Injection (ESI) mass spectrometer.
J = 12.0 Hz, 1H), 4.86–4.81 (m, 2H), 4.74 (d, J = 12.0 Hz, 1H), 4.70 (d,
J = 12.0 Hz, 1H), 4.60 (d, J = 12.0 Hz, 1H), 4.59–4.54 (m, 1H),
4.50–4.46 (m, 3H), 4.05–4.01 (m, 1H), 3.97 (t, J = 12.0 Hz, 1H),
3.89–3.78 (m, 1H), 3.72–3.68 (m, 1H), 3.65–3.56 (m, 3H), 3.05 (d, J =
4.0 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ 169.9, 138.7, 138.6, 138.5,
138.4, 138.3, 138.1, 138.0, 137.9, 128.5, 128.4, 128.4, 128.2, 128.1,
128.0, 128.0, 127.9, 127.8, 127.7, 127.7, 127.6, 127.6, 98.2, 97.5, 92.8,
91.3, 84.6, 83.2, 81.8, 80.1, 79.8, 77.9, 77.8, 75.7, 75.1, 74.9, 74.7,
73.5, 72.2, 72.0, 71.7, 71.3, 70.4, 69.7, 69.0, 68.7. HRMS (ESI-TOF) m/z
calcd for C43H44O7 (M + Na)+ 695.2985, found 695.2990.
General procedure for the synthesis of 1,3,4,5-tetra-O-benzyl-L-sor-
bopyranose (2).
Method I: To the solution of 2,3,4,6-tetra-O-benzyl-D-glucopyranose
(1) (1.08 g, 1 equiv, 2 mmol) in toluene (20 mL) was added MgnBu2 (1
mL, 1.0 mol/L, 0.5 equiv, 1 mmol) slowly. The mixture was heated to
80 ◦C for 6 h, then quenched by saturated NH4Cl solution (20 mL). The
mixture was extracted with EtOAc. The combined organic extracts were
washed by brine, dried over anhydrous NaSO4, and concentrated in
vacuo. Purification of the residue by column chromatography (30%
EtOAc/hexane) gave 1,3,4,5-tetra-O-benzyl-L-sorbopyranose (2) (821
mg, 76% yield) as colorless oil.
Declaration of competing interest
Method II: To the solution of 2,3,4,6-tetra-O-benzyl-D-glucopyranose
(1) (1.08 g, 1 equiv, 2 mmol) in toluene (20 mL) was added MgnBu2 (1
mL, 1.0 mol/L, 0.5 equiv, 1 mmol) and benzyl 2-(triphenylphosphor-
anylidene) acetate (82 mg, 10 mol%, 0.2 mmol). The mixture was
heated to 80 ◦C for 6 h, then quenched by saturated NH4Cl solution (20
mL). The mixture was extracted with EtOAc. The combined organic
extracts were washed by brine, dried over anhydrous NaSO4, and
concentrated in vacuo. Purification of the residue by column chroma-
tography (20% EtOAc/hexane) gave 1,3,4,5-tetra-O-benzyl-L-sorbopyr-
anose (2) (940 mg, 87% yield) as colorless oil and benzyl 2-((3S,5R,6R)-
3,4,5-tris(benzyloxy)-6-((benzyloxy)methyl)tetrahydro-2H-pyran-2-yl)
acetate (2’) (67 mg, 5% yield) as white solid.
The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgments
This work was supported by grants from the National Natural Science
Foundation of China (21702025, 21978039), Science and Technology
Innovation Foundation of Dalian City (2019J12GX029), the Funda-
mental Research Funds for the Central Universities (DUT20YG120).
References
1,3,4,5-tetra-O-benzyl-L-sorbopyranose (2) 1H NMR (400 MHz,
CDCl3) δ 7.35–7.15 (m, 18H), 7.17–7.15 (m, 2H), 4.96 (d, J = 12.0 Hz,
1H), 4.84 (t, J = 12.0 Hz, 2H), 4.73 (d, J = 12.0 Hz, 1H), 4.64 (d, J =
12.0 Hz, 1H), 4.56–4.48 (m, 3H), 3.95 (t, J = 8.0 Hz, 1H), 3.78–3.75 (m,
2H), 3.65–3.62 (m, 1H), 3.48 (d, J = 12.0 Hz, 1H), 3.40 (d, J = 12.0 Hz,
1H), 3.32 (d, J = 12.0 Hz, 1H), 3.26 (s, 1H). 13C NMR (101 MHz, CDCl3)
δ 138.7, 138.3, 137.8, 137.4, 128.5, 128.4, 128.4, 128.3, 128.1, 128.0,
127.9, 127.9, 127.8, 127.8, 127.7, 97.4, 82.8, 78.7, 78.5, 75.8, 75.4,
73.8, 73.2, 71.9, 61.0. HRMS (ESI-TOF) m/z calcd for C34H36O6 (M +
H)+ 541.2590, found 541.2594. All the spectra matched with those
previously reported [11].
2-((3S,5R,6R)-3,4,5-tris(benzyloxy)-6-((benzyloxy)methyl)tet-
rahydro-2H-pyran-2-yl)acetate (2’) White solid (4:1 anomers
mixture). 1H NMR (400 MHz, CDCl3) for major anomer (
α anomer) δ
7.37–7.12 (m, 23H), 7.17–7.12 (m, 2H), 5.22 (t, J = 4.0 Hz, 1H), 4.95 (d,
4