LETTER
Microwave-Assisted b-GlcN-Acylation
3113
Table 2 H2SO4-Silica Promoted Direct Glycosylation of N-Acetyl Glycosylamines under Microwave Conditions (continued)
Entry
9
Donor
Acceptor
Product
Yield (%)
OAc
OAc
OAc
O
OAc
O
3
8217
OBn
OAc
NHAc
AcO
AcO
NHAc
2
21
OAc
O
OH
O
AcO
AcO
O
BnO
BnO
BnO
BnO
5317
O
10
1
AcHN
BnO
OMe
BnO
OMe
11
22
OAc
O
AcO
AcO
O
OH
O
O
O
NHAc
O
11
1
4817
O
O
O
O
O
O
12
23
General Procedure for Glycosylation with Alcohols
Dodecyl 2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-b-D-glucopy-
ranoside (15)
A mixture of per-O-acetylated N-acetyl glycosamine (1 or 2, 585
mg, 1.5 mmol), alcohol (1 mmol), and H2SO4–silica (10 mg) in dry
DCE (3 mL) was placed in a 5 mL microwave reaction vial with a
stirring bar and heated under microwave conditions using a Biotage
Initiator 1 microwave reactor at 110 °C for 15 min. After comple-
tion, the mixture was filtered through Celite and washed with
CH2Cl2 ensuring complete recovery. The filtrate was washed suc-
cessively with sat. NaHCO3 (2 × 10 mL) and brine (10 mL). The or-
ganic layer was separated, dried (Na2SO4), filtered, and evaporated
in vacuo. The crude product thus obtained was purified by flash
chromatography using n-hexane–EtOAc (3:1) as eluant to afford
pure compounds.
1H NMR (500 MHz, CDCl3): d = 5.54 (d, 1 H, J = 8.5 Hz, NH), 5.24
(dd, 1 H, J2,3 = 8.5 Hz, J3,4 = 10.5 Hz, H-3), 4.99 (t, 1 H, J3,4, J4,5
8.5 Hz, H-4), 4.62 (d, 1 H, J1,2 = 8.0 Hz, H-1), 4.19 (dd, 1 H, J5,6a
5.0 Hz, J6a,6b = 12.0 Hz, H-6a), 4.06 (dd, 1 H, J5,6b = 2.5 Hz, J6a,6b
12.0 Hz, H-6b), 3.80–3.74 (m, 2 H, H-2, OCH2C11H23), 3.63 (m, 1
H, H-5), 3.40 (m, 1 H, OCH2C11H23), 2.01, 1.96, 1.95 (3 s, 9 H,
=
=
=
3 × COCH3), 1.87 (s,
3 H, NHCOCH3), 1.48 (m, 2 H,
OCH2CH2C10H21), 1.18 (m, 18 H, OCH2CH2C9H18-CH3), 0.81 (t, 3
H, J = 6.5 Hz, OCH2C10H20CH3). 13C NMR (125 MHz, CDCl3): d =
170.9 (NHCOCH3), 170.7, 170.2, 169.4 (3 × COCH3), 100.7 (C-1),
72.4, 71.8, 70.0, 68.8, 62.2 (C-6), 54.9 (C-2), 31.9, 29.6, 29.5, 29.3,
25.9, 23.3, 22.7 (NHCOCH3), 20.8, 20.7, 20.6 (3 × COCH3), 14.1
(dodecyl-CH3).
General Procedure for Glycosylation with Sugar Acceptors
A mixture of per-O-acetylated N-acetyl glucosamine (1, 780 mg, 2
mmol), sugar acceptor (1 mmol), and H2SO4–silica (10 mg) in dry
DCE (3 mL) was placed in a 5 mL microwave reaction vial with a
stirring bar and was heated under microwave conditions at 110 °C
for 30 min. The purification procedure was the same as above.
Bromopropyl 2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-b-D-gluco-
pyranoside (16)
1H NMR (500 MHz, CDCl3): d = 5.51 (d, 1 H, J = 9.0 Hz, NH), 5.20
(dd, 1 H, J2,3 = 8.5 Hz, J3,4 = 9.5 Hz, H-3), 5.07 (t, 1 H, J3,4, J4,5
8.5 Hz, H-4), 4.58 (d, 1 H, J1,2 = 8.0 Hz, H-1), 4.25 (dd, 1 H, J5,6a
4.5 Hz, J6a,6b = 12.0 Hz, H-6a), 4.13 (dd, 1 H, J5,6b = 2.0 Hz, J6a,6b
=
=
=
Octyl 2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-b-D-glucopyran-
oside (14)
12.0 Hz, H-6b), 4.01–3.94 (m, 2 H, H-2, OCH2CH2CH2Br), 3.70–
3.65 (m, H, H-5, OCH2CH2CH2Br), 3.49 (m, H,
1H NMR (500 MHz, CDCl3): d = 5.49 (d, 1 H, J = 9.0 Hz, NH), 5.31
2
2
(dd, 1 H, J2,3 = 9.0 Hz, J3,4 = 9.5 Hz, H-3), 5.07 (t, 1 H, J3,4, J4,5
9.5 Hz, H-4), 4.68 (d, 1 H, J1,2 = 8.5 Hz, H-1), 4.26 (dd, 1 H, J5,6a
4.5 Hz, J6a,6b = 12.0 Hz, H-6a), 4.13 (dd, 1 H, J5,6b = 2.0 Hz, J6a,6b
12.0 Hz, H-6b), 3.87–3.80 (m, 2 H, H-2, OCH2C7H15), 3.70 (m, 1 H,
H-5), 3.46 (m, 1 H, OCH2C7H15), 2.10, 2.03, 2.02 (3 s, 9 H,
=
=
=
OCH2CH2CH2Br), 2.17, 2.02 (2 m, 2 H, OCH2CH2CH2Br), 2.08,
2.03, 2.02 (3 s, 9 H, 3 × COCH3), 1.97 (s, 3 H, NHCOCH3). 13C
NMR (125 MHz, CDCl3): d = 171.1 (NHCOCH3), 170.7, 170.2,
169.4 (3 × COCH3), 101.6 (C-1), 72.5, 71.9, 68.5, 67.3, 62.1 (C-6),
54.5 (C-2), 32.1, 29.7, 29.5, 29.2, 23.4 (NHCOCH3), 20.8, 20.7,
20.6 (3 × COCH3).
3 × COCH3), 1.95 (s,
3 H, NHCOCH3), 1.57 (m, 2 H,
OCH2CH2C6H13), 1.26 (m, 10 H, OCH2CH2C5H10CH3), 0.88 (t, 3 H,
J = 6.5 Hz, OCH2C6H12CH3). 13C NMR (125 MHz, CDCl3): d =
170.9 (NHCOCH3), 170.7, 170.1, 169.4 (3 × COCH3), 100.7 (C-1),
72.4, 71.8, 70.0, 68.7, 62.2 (C-6), 55.0 (C-2), 31.9, 29.7, 29.3, 25.9,
23.3, 22.6 (NHCOCH3), 20.7, 20.6, 20.5 (3 × COCH3), 14.1 (octyl-
CH3).
Propargyl 2-Acetamido-3,4,6-tri-O-acetyl-2-deoxy-b-D-gluco-
pyranoside (19)
1H NMR (500 MHz, CDCl3): d = 5.54 (d, 1 H, J = 9.0 Hz, NH), 5.23
(dd, 1 H, J2,3 = 8.5 Hz, J3,4 = 9.5 Hz, H-3), 5.17 (t, 1 H, J3,4, J4,5
=
8.5 Hz, H-4), 5.01 (m, 2 H, OCH2C≡CH), 4.62 (d, 1 H, J1,2 = 8.0 Hz,
H-1), 4.31 (dd, 1 H, J5,6a = 4.0 Hz, J6a,6b = 12.0 Hz, H-6a), 4.18 (dd,
1 H, J5,6b = 2.5 Hz, J6a,6b = 12.0 Hz, H-6b), 4.01 (m, 1 H, H-2), 3.73
(m, 1 H, H-5), 2.28 (t, 1 H, J = 2.5 Hz, OCH2C≡CH), 2.07, 2.02,
2.00 (3 s, 9 H, 3 × COCH3), 1.95 (s, 3 H, NHCOCH3). 13C NMR
Synlett 2009, No. 19, 3111–3114 © Thieme Stuttgart · New York