S-Linked Thiomimetics of Phytoalexin Elicitor Active, Branched Oligosaccharides
FULL PAPER
(2,3,4,6-tetra-O-acetyl-β--glucopyranosyl)-3-thio-α--gluco- S-(β-
furanose (5, 400 mg, 0.66 mmol) in TFA/H2O, 9:1 (5 mL) was dithio-β-
D
-Glucopyranosyl)-(1Ǟ6)-S-[3-S-(β-
-glucopyranosyl]-(1Ǟ6)-S-(6-thio-β-
(1Ǟ6)-S-[3-S-(β- -glucopyranosyl)]-3,6-dithio-D
D
-glucopyranosyl)-3,6-
-glucopyranosyl)-
-glucopyranose
D
D
stirred under vacuum (water pump) for 40 min at 30°C until no
more acetone distilled. Subsequent freeze-drying of the solution
gave 6 which was used without further purification.
D
(12): (a) Methanolic NaOMe (1 , 1 mL) was added to a solution
of the acetylated hexathiosaccharide 11 (80 mg, 0.04 mmol) in
MeOH (10 mL), and the mixture was stirred for 50 h at room temp.
The solution was then demineralized with Amberlite ion-exchange
resin IRN 77(Hϩ). Concentration of the solution gave a syrup
which was subjected to reverse-phase LC (Lichrosorb NH2, 7 µm,
MeCN/water, 78:22) and freeze-dried to give 12 as a foam (45 mg,
100%). Ϫ [α]D ϭ Ϫ16.69 (c ϭ 0.59, H2O). Ϫ 13C NMR (50.3 MHz,
D2O): δ ϭ 97.3 (C-1Ib), 91.7 (C-1Ia), 88.3, 86.3, 84.6, 81.6, 80.5 (C-
1IIϪVI), 57.6 (C-3Ib), 56.1 (C-3IV), 54.7 (C-3Ia), 32.9, 32.4 (C-
6I,III,IV). Ϫ FAB MS; m/z (%):1093 (43) [M ϩ Na]ϩ. Ϫ (b) Conven-
tional O-deacetylation of 15 (130 mg, 0.07 mmol) in MeOH (10
mL) with methanolic NaOMe (1 , 0.15 mL) for 18 h at room
temp., followed by concentration and treatment of the residue with
TFA/water, 9:1 (1.4 mL) for 10 min at room temp., afforded 12 (63
mg, 85%), identical in all respects to the product obtained in (a).
1,2,4-Tri-O-acetyl-3-S-(2,3,4,6-tetra-O-acetyl-β-
D-glucopyranosyl)-
6-O-methoxytrityl-3-thio-α and β- -glucopyranose (7 and 8):
D
Chloro(4-methoxyphenyl)diphenylmethane (1 g, 1.4 equiv.) was ad-
ded to a solution of 6 (1.25 g, 2.3 mmol) in pyridine (18 mL) at
0°C. The mixture was stirred for 18 h at room temp. and then
acetylated by addition of Ac2O (18 mL) and further stirring for 2
h. Compounds 7 and 8 (2.0 g, 90%) were obtained as a 1:1 mixture
which could be separated by column chromatography (EtOAc/
petroleum ether, 1:3). Ϫ 7: Ϫ M.p. 165Ϫ166°C (ethanol). Ϫ [α]D ϭ
ϩ 13.3 (c ϭ 0.42, CHCl3). Ϫ 8: Ϫ M.p. 203Ϫ204°C (ethanol). Ϫ
[α]D ϭ ϩ 10.8 (c ϭ 0.37, CHCl3). Ϫ 13C NMR (50.3 MHz, CDCl3):
Table 2. Ϫ FAB MS; m/z (%): 947 (15) [M ϩ Na]ϩ, 273 (100)
[C(C6H5)2C6H4OMe]ϩ. Ϫ C46H52O18S (924.9): calcd. C 59.74, H
5.63, S 3.46; found C 59.17, H 5.73, S 3.25.
2,3,4-Tri-O-acetyl-1-S-acetyl-6-S-[2,4-di-O-acetyl-3,6-di-S-(2,3,4,6-
1,2,4-Tri-O-acetyl-3-S-(2,3,4,6-tetra-O-acetyl-β-
D-glucopyranosyl)-
tetra-O-acetyl-β-
D-glucopyranosyl)-3,6-dithio-β-D-glucopyranosyl]-
3-thio-β- -glucopyranose (9): A solution of 8 (1.82 g, 1.97 mmol)
D
1,6-dithio-β- -glucopyranose (13): A mixture of the bromide 2 (240
D
in aqueous 80% AcOH (80 mL) was stirred for 8 h at room temp.
(TLC; hexane/acetone, 1:1), then the mixture was concentrated un-
der reduced pressure and the volatiles were coevaporated with tolu-
ene. Column chromatography of the residue (hexane/acetone, 2:1)
gave 9 (1.15 g, 89.5%): Ϫ M.p. 196Ϫ197°C (hexane/acetone, 1:1).
Ϫ [α]D ϭ ϩ 7 (c ϭ 0.2, CHCl3). Ϫ 13C NMR (50.3 MHz, CDCl3):
Table 2. Ϫ FAB MS; m/z (%): 675 (20) [M ϩ Na]ϩ, 331 (70). Ϫ
CH36O17S (652.3): calcd. C 47.85, H 5.52, S 4.91; found C
47.66, H 5.46, S 4.82.
mg, 0.18 mmol) and potassium thioacetate (66 mg, 0.58 mmol) in
DMF (3 mL) was stirred overnight at room temp. and concentrated
under reduced pressure. The resulting residue was treated with
CH2Cl2 (10 mL), washed with water (2 ϫ 8 mL), dried (MgSO4),
and concentrated. Purification by column chromatography
(EtOAc/petroleum ether, 2:1) yielded 13 (155 mg, 65%) as a syrup.
Ϫ [α]D ϭ Ϫ18.0 (c ϭ 1.0, CHCl3). Ϫ 1H NMR (400 MHz, CDCl3):
δ ϭ 5.21 (d, 1 H, J1,2 ϭ 9.3 Hz, H-1I), 5.20 (t, 1 H, J2,3 ϭ J3,4
ϭ
9.3 Hz, H-3I), 5.19 (t, 1 H, J2,3 ϭ J3,4 ϭ 9.8 Hz, H-3III), 5.15 (t, 1
H, J2,3 ϭ J3,4 ϭ 9.3 Hz, H-3IV), 5.13 (t, 1 H, J2,3 ϭ 9.3 Hz, H-2I),
5.06 (t, 1 H, J4,5 ϭ 9.8 Hz, H-4III), 5.04 (t, 1 H, J4,5 ϭ 9.3 Hz, H-
4IV), 5.02 (t, 1 H, J1,2 ϭ 9.8 Hz, H-2III), 4.94 (dd, 1 H, J4,5 ϭ 10.1
Hz, H-4I), 4.90 (t, 1 H, J1,2 ϭ J2,3 ϭ 10.7 Hz, H-2II), 4.85 (dd, 1
H, J1,2 ϭ 10.0 Hz, H-2IV), 4.61 (d, 1 H, H-1II), 4.58 (d, 1 H, H-
1IV), 4.64 (dd, 1 H, J3,4 ϭ 10.7, J4,5 ϭ 9.4 Hz, H-4II), 4.21 (dd, 1
H, J6a,6b ϭ 12.4, J5,6b ϭ 4.5 Hz, H-6bIV), 4.10 (dd, 2 H, H-6aIII,IV),
3.81 (ddd, 1 H, J5, 6b ϭ 6.1, J5,6a ϭ 4.5 Hz, H-5I), 3.67 (ddd, 2 H,
J5,6a ϭ 2.1 Hz, H-5III,IV), 3.48 (ddd, 1 H, J5,6b ϭ 6.6, J5,6a ϭ 4.8
Hz, H-5II) , 2.75 (m, 4 H, H-6aI,II, H-6bI,II). Ϫ 13C NMR (50.3
MHz, CDCl3), Table 2. Ϫ FAB MS; m/z (%): 1341 [M ϩ Na]ϩ.
1,2,4-Tri-O-acetyl-6-deoxy-6-iodo-3-S-(2,3,4,6-tetra-O-acetyl-β-
D-
glucopyranosyl)-3-thio-β- -glucopyranose (10): Trifluoromethanes-
D
ulfonic anhydride (0.075 mL, 0.43 mmol) and 2,6-di-tert-butyl-4-
methylpyridine (90 mg, 0.43 mmol) were dissolved in CH2Cl2 (5
mL) and 9 (200 mg, 0.31 mmol) in CH2Cl2 (10 mL) was added to
this solution. After stirring at room temp. for 1 h, tetrabutylam-
monium iodide (342 mg, 0.93 mmol) was added. The mixture was
kept for 1 h, neutralized with satd. aqueous NaHCO3 and extracted
with chloroform. The extract was dried (MgSO4), and concen-
trated. Recrystallization from ethanol afforded 10 (190 mg, 80%).
Ϫ M.p. 222Ϫ223°C (ethanol). Ϫ [α]D ϭ ϩ 25.0 (c ϭ 0.4, CHCl3).
Ϫ
13C NMR (50.3 MHz, CDCl3): Table 2. Ϫ FAB MS; m/z (%):
S-(2,3,4,6-Tetra-O-acetyl-β-
acetyl-3-S-(2,3,4,6-tetra-O-acetyl-β-
-glucopyranosyl]-(1Ǟ6)-S-(2,3,4-tri-O-acetyl-6-thio-β-
pyranosyl)-(1Ǟ6)-S-[5-O-acetyl-3-S-(2,3,4,6-tetra-O-acetyl-β-
gluco-pyranosyl)-1,2-O-isopropylidene]-3,6-dithio-α- -gluco-
-glucopyranosyl)-3,6-dithio-β- furanose (15): (a) Sodium hydride (2.6 mg, 0.11 mmol) was added
-glucopyranosyl]-(1Ǟ6)-S-(2,3,4-tri-O-acetyl-6-thio-β-
-gluco- under N2 to a solution of the thiol 22[2] (100 mg, 0.1 mmol) in dry
pyranosyl)-(1Ǟ6)-S-[1,2,4-tri-O-acetyl-3-S-(2,3,4,6-tetra-O-acetyl- THF (10 mL). The suspension was stirred until hydrogen evolution
β- -glucopyranosyl)]-3,6-dithio-β- -glucopyranose (11): Sodium hy- had ceased. The resulting solution was then concentrated under
dride (5 mg, 0.21 mmol) was added under N2 to a solution of the reduced pressure and the residue dissolved in DMF (5 mL). 20 (102
D
-glucopyranosyl)-(1Ǟ6)-S-[2,4-di-O-
-glucopyranosyl)-3,6-dithio-β-
-gluco-
785 (20) [M ϩ Na]ϩ, 703 (70) [M Ϫ OAc]ϩ, 331 (100). Ϫ
C26H35IO16S (762.5): calcd. C 40.94, H 4.59, S 4.20; found C 40.87,
H 4.64, S 4.02.
D
D
D
D
-
S-(2,3,4,6-Tetra-O-acetyl-β-
D
-glucopyranosyl)-(1Ǟ6)-S-[2,4-di-O-
D
acetyl-3-S-(2,3,4,6-tetra-O-acetyl-β-
D
D
D
D
D
thiol 4 (170 mg, 0.13 mmol) in THF (10 mL) at room temp. The
suspension was stirred until hydrogen evolution had ceased. The
resulting solution was then concentrated under reduced pressure,
and the amorphous residue was dissolved in DMF (3 mL). 10 (107
mg, 0.14 mmol) in DMF (5 mL) was then added to this stirred
solution. After 1 h at room temp., conventional work up and col-
umn chromatography (petroleum ether/EtOAc/acetone, 4:2:1) gave
mg, 0.1 mmol) was added to this solution and the mixture stirred
for 4 h at 70°C, then concentrated. A solution of the residue in
CH2Cl2 (10 mL), was washed with water (8 mL), dried (MgSO4),
and concentrated to a syrup which was purified by column chroma-
tography (EtOAc/petroleum ether, 2:1) yielding 15 as an amorph-
ous solid (38 mg, 20%). Ϫ [α]D ϭ Ϫ30 (c ϭ 1.0, CHCl3). Ϫ 1H
NMR (400 MHz, CDCl3): δ ϭ 5.95 (d, 1 H, J1,2 ϭ 3.5 Hz, H-1I),
11 (210 mg, 83%) as an amorphous solid. Ϫ [α]D ϭ Ϫ19.92 (c ϭ 4.78 (d, 1 H, J1,2 ϭ 10.1 Hz, H-1II), 4.68 (d, 2 H, J1,2 ϭ 10.1 Hz,
0.50, CHCl3). Ϫ 1H NMR (500 MHz, CDCl3): Table 1. Ϫ 13C H-1V,VI), 4.61 (d, 2 H, J1,2 ϭ 10.1 Hz, H-1III,IV), 3.53 (d, 1 H, J3,4 ϭ
NMR (125.7 MHz, CDCl3): Table 2. Ϫ C76H102O46S5 (1911.9):
calcd. C 47.75, H 5.34, S 8.37; found C 47.34, H 5.64, S 8.81.
4.2 Hz, H-3I), 2.96 (t, 1 H, J2,3 ϭ J3,4 ϭ 10.1 Hz, H-3III). Ϫ 13C
NMR (50.3 MHz, CDCl3): δ ϭ 104.9 (C-1I), 85.3, 84.7, 83.2, 82.3,
Eur. J. Org. Chem. 1999, 1143Ϫ1152
1149