The Journal of Organic Chemistry
Note
combined organic layers were washed with saturated NaHCO3 (10
mL) followed by saturated sodium chloride (10 mL). The solution was
dried with Na2SO4 and concentrated using rotary evaporation, which
gave a whitish oil. Purification by column chromatography gave a white
solid (24 mg, 48% yield): 1H NMR (500 MHz, CDCl3) δ 7.79 (d, J =
7.8 Hz, 1H, CH), 7.45−7.34 (m, 2H, CH), 7.27−7.19 (m, 3H, CH),
7.19−7.13 (m, 1H, CH), 7.11−7.02 (m, 2H, CH), 4.26 (s, 1H,
ArPhCHNMe2), 2.34 (s, 3H, ArCH3), 2.18 (s, 6H, 2 x CH3); 13C{1H}
NMR (126 MHz, chloroform-d) δ 142.6 (4 °C), 141.6 (4 °C), 135.6
(4 °C), 130.6 (CH), 128.6 (CH), 128.5 (CH), 127.2 (CH), 127.0
(CH), 126.5 (CH), 126.4 (CH), 73.0 (ArPhCHNMe2), 45.1 (ArCH3),
20.1 (NCH3); HRMS (ESI-TOF) m/z calcd for C16H20N 226.1596
([M + H]+); found 226.1601; crystals suitable for X-ray crystallog-
raphy were obtained by evaporation from CDCl3 (CCDC 1496558).
Spectroscopic data were in agreement with literature data.25
Synthesis of 3,4,6-tri-O-benzyl-D-galactal 2 Free of Impurity
4. Under a N2 atm, D-galactal (1.75 g, 12 mmol) was dissolved in
anhydrous DMF (50 mL). The flask was cooled to 0 °C (50:50 ice/
water), and NaH (60% dispersion in mineral oil) (2.14 g, 53.5 mmol)
was added to the reaction flask. The ice bath was removed, and the
reaction was left to stir at room temperature for 30 min. The flask was
again cooled to 0 °C, and BnBr (5.5 mL, 46 mmol) was added
dropwise to the reaction mixture. The ice bath was removed, and the
reaction mixture was left to stir at room temperature for 36 h. TLC
analysis (4:1 cyclohexane/ethyl acetate; H2SO4 stain (15−10%
EtOH)) showed that the starting galactal (baseline spot) was
consumed and three spots were present in the reaction mixture (Rf
= 0.67, 0.33, 0.03). The reaction was quenched with MeOH (2 mL),
and the solvents were removed using rotary evaporation. The crude
mixture was dissolved in cyclohexane (100 mL) and washed with 1 M
HCl (2 × 30 mL), then saturated NaHCO3 (1 × 30 mL) and
deionized H2O (30 mL). The organic layer was dried using MgSO4
AUTHOR INFORMATION
Corresponding Author
Notes
■
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
A.C.C. thanks the Irish Research Council for funding (GOIPG/
2013/301). E.M.M. thanks Science Foundation Ireland & the
Marie-Curie Action COFUND (11/SIRG/B2154) for financial
support.
REFERENCES
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mmol, 1 equiv), and thiourea catalyst 1 (1.5 mg, 0.003 mmol, 1 mol
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ASSOCIATED CONTENT
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Kolehmainen, E.; Rissanen, K. New J. Chem. 2004, 28, 1426−1430.
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* Supporting Information
́
(25) Zdrojewski, T.; Jonczyk, A. J. Org. Chem. 1998, 63, 452−457.
The Supporting Information is available free of charge on the
(26) Durantie, E.; Bucher, C.; Gilmour, R. Chem. - Eur. J. 2012, 18,
8208−8215.
NMR spectra for compounds 3b and 4, glycosylation
reactions, NMR titration of 1 vs 4, HPLC chromato-
grams for compound 2 contaminated with impurity 4,
and X-ray crystal structure for compound 4 (PDF)
C
J. Org. Chem. XXXX, XXX, XXX−XXX