238
A. Tauss et al. / Tetrahedron: Asymmetry 17 (2006) 234–239
6.8 Hz, H-4), 3.87 (m, 1H, H-5), 3.82 (dd, 1H, H-2), 3.30
protected septanose 13 (2.25 g, 88%). Found: C, 68.38;
H, 4.80; C34H28O10 (596.5963) requires: C, 68.45; H,
4.73; Mass spectrum (API-ES): m/z: 595.60 [MꢀH]; a-
anomer: dH (CDCl3) 6.13 (dd, 1H, J3,4 9.3 Hz, J4,5
9.3 Hz, H-4), 5.96 (dd, 1H, J2,3 9.8 Hz, H-3), 5.82 (dd,
0
0
(dd, 1H, J5,6 4.9 Hz, J6;6 9.5 Hz, H-6), 3.19 (dd, 1H, J5;6
4.9 Hz, H-60); dC (MeOH-d4) 73.9, 72.2, 71.8, 71.1 (C-2,
C-3, C-4, C-5), 65.2 (C-6), 54.6 (C-1).
0
4.2. 2,3,4,5-Tetra-O-benzoyl-6-O-trityl-L-idose diethyl-
dithioacetal 11
1H, J1,2 6.8 Hz, H-2), 5.59 (ddd, 1H, J5,6 9.8 Hz, J5;6
0
4.4 Hz, H-5), 5.38 (d, 1H, H-1), 4.30 (dd, 1H, J6;6
13.2 Hz, H-6), 4.04 (dd, 1H, H-60); dC (CDCl3) 96.2
(C-1), 74.0, 73.6, 72.3, 69.0 (C-2, C-3, C-4, C-5), 60.9
(C-6). b-Anomer: dH (CDCl3) 5.91 (d, 1H, J1,2 3.4 Hz,
H-1); dC (CDCl3) 92.9 (C-1), 75.2, 73.6, 72.7, 70.8 (C-
2, C-3, C-4, C-5), 61.2 (C-6).
To a solution of compound 10 (15.1 g, 28.6 mmol) in
pyridine (100 mL), benzoyl chloride (16.2 mL,
140 mmol) was added and the mixture stirred at ambient
temp for 16 h. Precipitated pyridinium hydrochloride
was removed by filtration and the solution was concen-
trated under reduced pressure. The remaining residue
was dissolved in CH2Cl2 and the organic layer sequen-
tially washed with 5% aqueous HCl, 5% aqueous
sodium bicarbonate and dried over Na2SO4. Filtration,
removal of the solvent and purification on silica gel gave
tetrabenzoate 11 (26.1 g, 97%) as a faintly yellow oil.
Found: C, 72.35; H, 5.60; C57H52O9S2 (945.1726)
4.5. 2,3,4,5-Tetra-O-benzoyl-a/b-L-idoseptanosyl fluoride
14
To a 3% solution of septanose 13 (1.73 g, 2.90 mmol) in
dry CH2Cl2, DAST (760 lL, 2 equiv) was added at
ꢀ50 ꢁC and the mixture stirred at ꢀ30 ꢁC until all the
starting materials had reacted. The reaction mixture
was carefully washed with 5% aqueous bicarbonate,
dried over Na2SO4 and filtered. Removal of the solvent
under reduced pressure furnished an anomeric mixture
(a/b ꢂ 1:10) of the septanosyl fluorides 14, which was
pure enough for the next step (1.69 g, 97%). Found: C,
68.14; H, 4.60; C34H27FO9 (598.5873) requires: C,
68.22; H, 4.55; Mass spectrum (API-ES): m/z: 597.50
[MꢀH]; b-anomer (main product) dH (CDCl3) 6.26
(dd, 1H, J3,4 9.8 Hz, J4,5 6.8 Hz, H-4), 6.02–5.87 (m,
3H, H-1, H-2, H-3), 5.60 (m, 1H, H-5), 4.62 (dd, 1H,
requires: C, 72.43; H, 5.55; Mass spectrum (API-ES):
20
m/z: 944.10 [MꢀH]; ½aꢁD ¼ þ6:2 ðc 1:6; CH2Cl2Þ; dH
(acetone-d6) 6.39 (dd, 1H, J3,4 4.4 Hz, J4,5 5.9 Hz,
H-4), 6.32 (dd, 1H, J2,3 5.9 Hz, H-3), 5.93 (dd, 1H, J1,2
5.4 Hz, H-2), 5.90 (m, 1H, H-5), 4.43 (d, 1H, H-1),
0
3.51 (dd, 1H, J5,6 5.6 Hz, J6;6 10.0 Hz, H-6), 3.39 (dd,
1H, J5;6 4.6 Hz, H-60); dC (acetone-d6) 73.0, 71.8, 70.9,
0
70.0 (C-2, C-3, C-4, C-5), 61.8 (C-6), 51.7 (C-1).
4.3. 2,3,4,5-Tetra-O-benzoyl-6-O-trityl-L-idose 12
J5,6 1.7 Hz, J6;6 13.8 Hz, H-6), 4.28 (m, 1H, H-60); dC
0
To a 3% solution of compound 11 (1.61 g, 1.70 mmol) in
a mixture of acetone/H2O/CH3CN 2:1:2 (v/v/v) HgO
(590 mg, 1.6 equiv) and HgCl2 (740 mg, 1.6 equiv) were
added and the mixture stirred at 60 ꢁC for 18 h until
TLC indicated complete conversion of the starting
material. Salts were removed by filtration and washed
with acetone. The reaction mixture was concentrated
under reduced pressure and the residue was dissolved
in CH2Cl2. This solution was consecutively washed with
1 M aqueous KI solution and saturated aqueous sodium
thiosulfate and dried (Na2SO4). Evaporation of the sol-
vent and purification on silica gel furnished unstable free
aldehyde 12 (1.39 g, 97%) as an oil, which was used
immediately in the next step. Found: C, 75.82; H,
5.11; C53H42O10 (838.9197) requires: C, 75.88; H, 5.05;
(CDCl3) 106.6 (JC,F 230.1 Hz, C-1), 73.5, 71.9 (C-4, C-
5), 71.9 (JC,F 25.4 Hz, C-2), 70.3 (JC,F 2.9 Hz, C-3),
61.6 (JC,F 4.8 Hz, C-6). a-Anomer: dC (CDCl3) 108.8
(JC,F 229.3 Hz, C-1), 74.2, 71.3 (C-4, C-5), 70.8 (JC,F
34.6 Hz, C-2), 67.7 (JC,F 8.0 Hz, C-3), 61.5 (C-6).
4.6. 4-Nitrophenyl 2,3,4,5-tetra-O-benzoyl-a-L-idosepta-
noside 15 and 4-nitrophenyl 2,3,4,5-tetra-O-benzoyl-b-L-
idoseptanoside 16
To a 3% solution of septanosyl fluoride 14 (380 mg,
0.635 mmol) in CH2Cl2 containing NEt3 (110 lL), 4-
nitrophenol (115 mg, 0.83 mmol) and a few drops of
BF3ÆEt2O in Et2O (1 M) were added. After 1 h, the mix-
ture was washed with 5% aqueous bicarbonate, dried
over Na2SO4, filtered and concentrated under reduced
pressure. Chromatography gave pure b-16 (190 mg,
42%) and a-septanosides (15, 175 mg, 38%). Found:
C, 66.87; H, 4.40; C40H31NO12 (717.6926) requires:
Mass spectrum (API-ES): m/z: 837.80 [MꢀH];
20
½aꢁD ¼ ꢀ13:8 ðc 1:7; CH2Cl2Þ; dH (acetone-d6) 9.77 (m,
1H, H-1), 6.62 (m, 1H, H-4), 6.28 (m, 1H, H-3), 6.05
(m, 1H, H-2), 5.91 (m, 1H, H-5), 3.51 (m, 2H, H-6, H-
60); dC (acetone-d6) 194.4 (C-1), 76.5, 71.8, 70.0, 69.8
(C-2, C-3, C-4, C-5), 62.1 (C-6).
C, 66.94; H, 4.35; Mass spectrum (API-ES): m/z:
20
716.60
[MꢀH];
a-anomer:
½aꢁD ¼ ꢀ23:8 ðc 2:1;
CH2Cl2Þ; dH (CDCl3) 6.19 (dd, 1H, J1,2 6.8 Hz, J2,3
9.7 Hz, H-2), 6.17 (dd, 1H, J3,4 9.7 Hz, J4,5 8.8 Hz,
H-4), 6.02 (dd, 1H, H-3), 5.83 (d, 1H, H-1), 5.61 (ddd,
4.4. 2,3,4,5-Tetra-O-benzoyl-L-idoseptanose 13
0
0
To a 3% solution of free aldehyde 12 (3.60 g, 4.29 mmol)
in CH2Cl2, MeOH (25 mL) and BF3ÆEt2O (1.1 equiv) in
Et2O were added at ambient temp. After 15–20 min,
CH2Cl2 (150 mL) was added and the mixture washed
with 5% aqueous bicarbonate until neutral and dried
over Na2SO4. Filtration, removal of the solvents under
reduced pressure and purification of the residue on silica
gel gave an anomeric mixture (a/b ꢂ 6:1) of partially
1H, J5,6 10.7 Hz, J5;6 4.4 Hz, H-5), 4.29 (dd, 1H, J6;6
13.2 Hz, H-6), 4.07 (dd, 1H, H-6); dC (CDCl3) 99.5
(C-1), 74.2, 71.6, 71.1, 68.3 (C-2, C-3, C-4, C-5), 60.6
20
(C-6). b-Anomer: ½aꢁD ¼ þ79:0 ðc 2:3; CH2Cl2Þ; dH
(CDCl3) 6.41 (dd, 1H, J3,4 5.9 Hz, J2,3 9.8 Hz, H-3),
6.08 (dd, 1H, J1,2 2.4 Hz, H-2), 5.94 (dd, 1H, J4,5
5.9 Hz, H-4), 5.91 (d, 1H, H-1), 5.58 (ddd, 1H, J5,6
0
0
2.2 Hz, J5;6 4.9 Hz, H-5), 4.43 (dd, 1H, J6;6 13.7 Hz,