Cyclic Trisaccharide
2281±2294
(FAB): m/z (%): 948 (8) [MK] , 932 (100) [MNa] ; HRMS(FAB): calcd
[MK] , 1330 (100) [MNa] ; MS (FAB): calcd C77H81NO18Na [MNa]
C52H60O12SNa [MNa] 931.37; found 931.37.
1330.54; found 1330.53.
Methyl 2,6-di-O-benzyl-3-O-(3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-a-
d-mannopyranoside-trichloroacetimidate 3'',4''-di-O-benzyl-2''-deoxy-2''-
phthalimido-b-d-glucopyranoside-4,6''-methylidene acetal (10): - Trichlor-
oacetonitrile (0.782 mL, 7.80 mmol) and 1,8-diazabicyclo[5.4.0]undec-7-ene
(19.5 mL, 0.13 mmol) were added to a solution of 9 (1.7 g, 1.3 mmol) in
CH2Cl2 (30 mL) and the reaction mixture was stirred under argon. After
20 min the TLC analysis (CH2Cl2/acetone, 95:5 v/v) showed almost
complete conversion of the starting material into the product. The mixture
was concentrated in vacuo and the oily residue was applied onto a column
of silica gel and eluted with acetone/CH2Cl2 (1:99 v/v). Concentration of the
appropriate fractions gave 10 as a white foam (1.22 g, 65% yield); Rf
Methyl
2,6-di-O-benzyl-3-O-(2-O-acetyl-3,4,6-tri-O-benzyl-a-d-manno-
pyranosyl)-a-d-mannopyranoside-p-methoxyphenyl 3'',4''-di-O-benzyl-2''-
deoxy-2''-phthalimido-b-d-glucopyranoside-4,6''-methylidene acetal (7): A
mixture of 5 (5.1 g, 5.62 mmol), p-methoxyphenyl 3,4-di-O-benzyl-2-deoxy-
2-phthalimido-b-d-glucopyranoside (6) (2.90 g, 4.88 mmol) and powdered
molecular sieves (8 g) was stirred for 1 h in a mixture of THF and 1,2-
dichloroethane (1:1 v/v, 100 mL) under argon. The solution was cooled to
08C. N-iodosuccinimide (1.35 g, 6 mmol) was dissolved in a mixture of THF
and 1,2-dichloroethane (60 mL, 1:1 v/v). Trifluoromethanesulfonic acid
(54 mL, 0.6 mmol) was then added and the solution stirred for further 30 s.
The resulting mixture (0.1m, 58.7 mL) was added quickly to the initial
solution which was then stirred for 30 min at 08C. TLC analysis indicated
the conversion of the starting material into a major product. The reaction
mixture was neutralized by the addition of triethylamine and filtered
through Celite. The resulting solution was diluted with CH2Cl2
(200 mL)and washed with Na2S2O3 (2 Â 100 mL), NaHCO3 (100 mL) and
brine (100 mL). The organic layer was dried (MgSO4), filtered, and
concentrated to dryness. Purification of the crude product by column
chromatography on silica gel (CH2Cl2/acetone, 98:2 v/v) afforded the
(acetone/CH2Cl2, 5:95 v/v) 0.50; [a]2D2 53.3 (CH2Cl2,
c
1
1
9.6 mgmL 1); H NMR (300 MHz, CDCl3): d 8.41 (s, 1H, C NH), 7.65
(brs, 4H, arom H -Pht), 7.40 ± 6.80 (m, 35H, arom H), 6.37 (d, 1H, J1'', 2''
8.5 Hz, H-1''), 5.15 (d, 1H, J1', 2' 1.1 Hz, H-1'), 4.87 (d, 1H, Jgem 11.4 Hz,
-CH2- benzyl), 4.85 (d, 1H, Jgem 11.0 Hz, -CH2- benzyl), 4.82 ± 4.35 (m,
17H, -OCH2O-, -CH2- benzyl, H-1, H-2'', H-3''), 4.15 (brs, 1H, H-2'), 4.03
(dd, 1H, J3, 2 3.3 Hz, J3, 4 9.2 Hz, H-3), 3.98 ± 3.52 (m, 14H, H-2, H-4,
H-5, H-6, H-3', H-4', H-5', H-6', H-4'', H-5'', H-6''), 3.31 (s, 3H, -OCH3),
13
3.10 (brs, 1H, -OH); C NMR (75 MHz, CDCl3): d 168.0 (C O), 160.9
trisaccharide 7 as a colorless oil (5.39 g, 76% yield); Rf (acetone/CH2Cl2,
22
4:96 v/v) 0.66; [a]
44.4 (CH2Cl2, c 26.8 mgmL 1); 1H NMR
(Cq imidate), 138.7, 137.9 (Cq benzyl), 133.8, 123.3 (arom C -Pht), 131.5 (Cq
-Pht), 128.5 ± 127.4 (arom C), 102.1, 98.3, 94.0 (C-1, C-1', C-1''), 97.6
(-OCH2O-), 80.2, 79.5, 78.9, 77.6, 75.7, 74.8, 74.6, 71.3, 68.4 (C-2, C-3, C-4,
C-5, C-2', C-3', C-4', C-5', C-3'', C-4'', C-5''), 74.9, 74.7, 73.5, 73.2, 72.1, 69.7,
69.5, 67.1 (-CH2- benzyl, C-6, C-6', C-6''), 54.8 (-OCH3, C-2''); MS (FAB):
ꢀkapDꢀ=kap
(300 MHz, CDCl3): d 7.65 (brs, 4H, arom H -Pht), 7.38 ± 6.85 (m, 35H,
arom H), 6.80, 6.65 (2 m, 4H, arom H -MP), 5.59 (d, 1H, J1'', 2'' 8.1 Hz,
H-1''), 5.56 (dd, 1H, J2', 1' 1.8 Hz, J2', 3' 3.3 Hz, H-2'), 5.21 (d, 1H, H-1'),
5.02 (d, 1H, Jgem 6.3 Hz, -OCH2O-), 4.94 ± 4.42 (m, 16H, H-1, -OCH2O-,
-CH2- benzyl), 4.40 (m, 1H, H-2''), 4.02 (dd, 1H, J3, 2 2.6 Hz, J3, 4 9.6 Hz,
H-3), 4.38 ± 3.53 (m, 15H, H-2, H-4, H-5, H-6, H-3', H-4', H-5', H-6', H-3'',
H-4'', H-5'', H-6''), 3.62 (s, 3H, -OCH3 -MP), 3.25 (s, 3H, -OCH3), 2.10 (s,
m/z (%) 1473 (73) [MNa3 Â 35Cl] , 1476 (100), [MNa2 Â 35Cl1 Â
37Cl] , 1479 (32) [MNa1 Â 35Cl2 Â 37Cl] ; HRMS (FAB): calcd
C79H81N2O1835Cl3Na
[MNa]
1473.44;
found
1473.44;
calcd
C79H81N2O1835Cl237ClNa [MNa]
1475.44; found 1475.44; calcd
3H, -CH3 acetyl); 13C NMR (75 MHz, CDCl3): d 170.0 (C O), 151.0 (Cq
C79H81N2O1835Cl37Cl2Na [MNa] 1477.44; found 1477.44.
-MP), 138.0 (Cq benzyl), 133.7, 123.3 (arom C -Pht), 131.6 (Cq -Pht), 128.5 ±
127.4 (arom C), 118.6, 114.4 (arom C -MP), 100.1, 98.8, 97.7 (C-1, C-1',
C-1''), 97.8 (-OCH2O-), 79.6, 79.1, 77.8, 77.5, 74.3, 74.1, 72.2 (C-2, C-3, C-4,
C-5, C-2', C-3', C-4', C-5', C-3'', C-4'', C-5''), 74.8, 73.4, 73.0, 72.1, 71.9, 69.8,
69.2, 67.5 (-CH2- benzyl, C-6, C-6'), 64.1 (C-6''), 55.9, 55.7, 54.8 (-OCH3 -MP,
-OCH3, C-2''), 21.1 (-CH3 acetyl); MS (FAB): m/z (%): 1478 (100)
Methyl
(1 !2)-(3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)-2,6-di-O-benzyl-
a-d-mannopyranoside-4,6''-methylidene acetal (11): mixture of 10
(3,4-di-O-benzyl-2-deoxy-2-phthalimido-b-d-glucopyranosyl)-
A
(1.22 g, 0.84 mmol) and 4 powdered molecular sieves (1 g) was stirred
for 30 min in CH2Cl2 (50 mL) under argon. The solution was cooled to
208C and trimethylsilyl trifluoromethanesulfonate (8 mL, 0.042 mmol)
was added and the reaction mixture was stirred for 10 min. The reaction
mixture was quenched by the addition of triethylamine and filtered through
Celite; the filtrate was diluted with CH2Cl2, and washed with NaHCO3 (2 Â
50 mL) and water (50 mL). The organic layer was dried (MgSO4), filtered,
and concentrated to dryness. Purification of the residue by column
chromatography on silica gel (CH2Cl2/acetone, 98:2 v/v) afforded the
cyclic trisaccharide 11 as a colorless oil (891.8 mg, 82% yield); Rf (CH2Cl2/
acetone, 96:4 v/v) 0.78; [a]2D2 42.1 (CH2Cl2, c 20.53 mgmL 1);
1H NMR (300 MHz, CDCl3): d 7.52 (brs, 4H, arom H-Pht), 7.41 ± 6.80
(m, 35H, arom H), 5.75 (2d, 2H, J1'', 2'' 7.7 Hz, H-1'', H-1'), 5.06 (d, 1H,
Jgem 4.0 Hz, -OCH2O-), 4.88 (d, 1H, Jgem 11.0 Hz, -CH2- benzyl), 4.67 (d,
1H, J1, 2 1.5 Hz, H-1), 4.83 ± 4.23 (m, 15H, -OCH2O-, -CH2- benzyl, H-2'',
H-2'), 4.15 (d, 1H, Jgem 10.7 Hz, -CH2- benzyl), 4.11 (dd, 1H, J3, 2 2.9 Hz,
H-3), 3.99 (2dd, 2H, J4, 3 9.9 Hz, H-4, H-4''), 3.82 ± 3.44 (m, 13H, H-2,
[MNa] ; HRMS (FAB): calcd C86H89NO20Na [MNa] 1478.59; found
1478.59.
Methyl 2,6-di-O-benzyl-3-O-(3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-a-
d-mannopyranoside-3'',4''-di-O-benzyl-2''-deoxy-2''-phthalimido-b-d-glu-
co-pyranose-4,6''-methylidene acetal (9): Potassium tert-butoxide (0.412 g,
3.67 mmol) was added to a solution of trisaccharide 7 (5.34 g, 3.67 mmol) in
methanol (50 mL). The resulting mixture was stirred at room temperature
under argon. After 4 h, TLC analysis (acetone/CH2Cl2, 3:97 v/v) showed
the complete conversion of the starting material. The reaction mixture was
neutralized with Dowex-50WX8-[H ] and filtered, and the filtrate con-
centrated to dryness in vacuo. The crude compound 8 was used without
further purification. Compound 8 was dissolved in a mixture of toluene/
acetonitrile/water (60 mL, 1:4:1 v/v/v), and cerium ammonium nitrate
(6.04 g, 11.01 mmol) was added. The mixture was stirred for 4 h at room
temperature under the exclusion of light, after which time the solution was
diluted with ethyl acetate. The organic layer was washed with saturated
NaHCO3 (2 Â 75 mL) and brine (75 mL), dried (MgSO4), and filtered, and
the filtrate concentrated under reduced pressure. The crude product was
purified by column chromatography on silica gel with acetone/CH2Cl2 (4:96
v/v) as the eluent. The trisaccharide 9 was obtained as a pale yellow oil
(2.16 g, 45% yield); Rf (acetone/CH2Cl2, 5:95 v/v) 0.20; [a]2D2 29.8
(CH2Cl2, c 20.8 mgmL 1); 1H NMR (300 MHz, CDCl3): d 7.80 ± 7.60
H-5, H-6, H-3', H-4', H-5', H-6', H-3'', H-5'', H-6''), 3.25 (s, 3H, -OCH3);
13
C NMR (75 MHz, CDCl3): d 167.9 (C O), 139.1, 138.4, 138.1, 137.9,
137.7 (Cq benzyl), 133.4, 123.1 (arom C -Pht), 131.6 (Cq -Pht), 128.5 ± 126.8
(arom C), 100.0, 99.0, 94.5 (C-1, C-1', C-1''), 96.9 (-OCH2O-), 79.2, 78.9,
77.2, 76.8, 76.0, 75.3, 74.5, 72.0, 71.8, 71.3 (C-2, C-3, C-4, C-5, C-2', C-3', C-4',
C-5', C-3'', C-4'', C-5''), 74.9, 74.3, 73.5, 73.2, 72.5, 72.3, 69.1, 68.8, 66.2
(-CH2- benzyl, C-6, C-6', C-6''), 54.7, 53.8 (C-2'', (-OCH3); MS (FAB): m/z
(%): 1328 (8) [MK] , 1312 (100) [MNa] ; HRMS (FAB): calcd
(4H, m, arom H -Pht), 7.41 ± 6.88 (m, 35H, arom H), 5.32 (d, 1H, J1', 2'
1.1 Hz, H-1'), 5.25 (d, 1H, J1'', 2'' 8.5 Hz, H-1''), 4.85 (2d, 2H, Jgem
C77H79NO17Na [MNa] 1312.52; found 1312.52.
11.0 Hz, -CH2- benzyl), 4.70 (d, 1H, J1, 2 1.4 Hz, H-1), 4.81 ± 4.39 (m,
15H, -OCH2O-, -CH2- benzyl, H-3''), 4.27 (brs, 1H, H-2'), 4.13 (dd, 1H,
J2'', 3'' 10.7 Hz, H-2''), 4.09 (m, 1H, H-3), 4.01 ± 3.54 (m, 14H, H-2, H-4,
Methyl
(3,4-di-O-benzyl-2-acetimido-2-deoxy-b-d-glucopyranosyl)-
(1 !2)-(3,4,6-tri-O-benzyl-a-d-mannopyranosyl)-(1 !3)-2,6-di-O-benzyl-
a-d-mannopyranoside-4,6''-methylidene acetal (12): Hydrazine monohy-
drate (1.78 mL, 36.69 mmol) was added to a solution of 11 (945.8 mg,
0.733 mmol) in EtOH (10 mL) and the reaction mixture was heated under
reflux for 18 h. TLC analysis with ninhydrin showed complete conversion
of the starting material into an amino-containing intermediate (Rf
(acetone/CH2Cl2, 4:96 v/v) 0.10). The solvent was removed in vacuo
and the residue coevaporated with toluene. The amine thus obtained was
subsequently dissolved in a mixture of pyridine (10 mL) and acetic
H-5, H-6, H-3', H-4', H-5', H-6', H-4'', H-5'', H-6''), 3.31 (s, 3H, -OCH3);
13
C NMR (75 MHz, CDCl3): d 168.2 (C O), 138.7, 138.4, 138.3, 138.2,
138.0 (Cq benzyl), 133.7, 123.2 (arom C -Pht), 131.8 (Cq -Pht), 128.5 ± 126.6
(arom C), 100.7, 98.6, 92.9 (C-1, C-1', C-1''), 97.6 (-OCH2O-), 79.7, 79.3, 79.2,
78.0, 76.3, 75.7, 74.6, 74.5, 71.7, 71.5, 68.3 (C-2, C-3, C-4, C-5, C-2', C-3', C-4',
C-5', C-3'', C-4'', C-5''), 74.8, 74.6, 73.4, 71.9, 69.5, 69.3 (-CH2- benzyl, C-6,
C-6', C-6''), 57.7, 54.9 (-OCH3, C-2''); MS (FAB): m/z (%): 1346 (3)
Chem. Eur. J. 1999, 5, No. 8
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1999
0947-6539/99/0508-2291 $ 17.50+.50/0
2291