Mercaptan derivative 5 was purified and added to cinnamyl alcohol (6). The synthesis was performed in anhydrous
CH Cl using a solution of I in CH CN as a catalyst. Acylated rosavin was hydrolyzed using the Zemplen reaction.
2
2
2
3
The product was purifiedin aconcentratingcartridgefilledwith reversed-phase sorbent (Diasorb130-C16T) toremove
residual cinnamyl alcohol and carbohydrates. The effluent from the cartridge contained chromatographically pure (HPLC
monitoring) rosavin. The structure of the synthetic rosavin was confirmed by NMR spectroscopy.
13
The C NMR and PMR spectra of rosavin exhibited chemical shifts that were consistent with the formation of a
β-D-glycoside bond between glucose and the aglycon (102.3, dd, and 4.5 ppm) and an α-L-glycoside bond between arabinose
and glucose (103.5 and 4.5 ppm, dd).
20
The angle ofrotation [α]
-56.3° (CHCl :MeOH) ofthe synthesized rosavin alsoconfirmed that it had been prepared
3
D
20
{lit. [α]
-56.5° (CHCl :MeOH) [6]}.
3
D
EXPERIMENTAL
13
Materials and Methods. PMR and C NMR spectra were recorded on a Bruker DRX 400 spectrometer at working
frequency 400 and 100 MHz, respectively, in DMSO-d with TMS.
6
HPLC wasperformedon aMillichrom-2 chromatograph with a 2/60-mm column packed with SilasorbC18 and elution
by CH OH:C H OH:H O (35:1:14) with UV detection at 252 nm and flow rate 50 µL/min; TLC, on Silufol plates (Czech Rep.)
3
4
9
2
using toluene:ethylacetate (6:1 and 4:1). The developer was phosphotungstic acid (20%) in ethanol with heating to 120°C for
1 min. Column chromatographywas carried out over silica gel L (100/160 µm) using toluene:ethylacetate (10:1-4:1) as eluent.
Diisopropylideneglucose(6) was prepared bytheliteraturemethod[7];2,3,4-tri-O-acetyl-β-L-arabinopyranosylbromide
(5), by the literature method [7], silver carbonate, by reacting silver nitrate with saturated Na CO solution in the dark and
2
3
drying the resulting yellow powder with anhydrous acetone and then in vacuo. Boron trifluoride etherate (BF ·OEt ) was
3
2
vacuum distilled. Crystalline iodine was purified bysublimation. Acetic anhydride(chemicallypure, Russia), silver perchlorate
(Sigma, USA) and methylmercaptan (Sigma, USA) were purchased commercially.
2,3,4-Tri-O-acetyl-α-L-arabinopyranosyl-(1→6′)-(1′,2′,3′,4′-diisopropylidene-D-glucopyranose) (2). A solution
of 1,2,3,4-diisopropylidene-α-D-glucopyranose (100 mg, 0.42 mmol) in anhydrous acetone (25 mL) was stirred, treated with
an equimolar amount ofglycosylatingagent 2,3,4-tri-O-acetyl-β-L-arabinopyranosylbromide(172.6 mg, 0.42 mmol) and a two-
fold excess of silver prechlorate (176 mg, 0.84 mmol) with CaCO (84 mg, 0.84 mmol), irradiated for 15 min in an ultrasonic
3
bath, and stirred for 1 d at room temperature. After the reaction was finished, the mixture was filtered. The solvent was
evaporated. The solid was chromatographed over a silica-gel column using toluene:ethylacetate (9:1-4:1). Yield of 2, 44.5 mg
(18%). The IR and NMR spectra are described in the text.
2,3,4-Tri-O-acetyl-α-L-arabinopyranosyl-(1→6′)-(2′,3′,4′-tri-O-acetyl-β-methyl-1′-thio-D-glucopyranoside)(5).
2,3,4-Tri-O-acetyl-α-L-arabinopyranosyl-(1→6′)-(1′,2′,3′,4′-tetra-O-acetyl-β-D-glucopyranoside)(1g, 1.6mmol)wasdissolved
in CHCl (10 mL) and treated with methylmercaptan (92 mg, 1.9 mmol) and then boron trifluoride etherate (542 mg, 8 mmol).
3
The mixture was stirred for 6 h, washed with saturated Na CO solution and water, and dried over anhydrous Na SO to afford
2
3
2
4
5 in 64% yield.
Total Acetate ofRosavin. 2,3,4-Tri-O-acetyl-α-L-arabinopyranosyl-(1-6′)-(2′,3′,4′-tri-O-acetyl-β-methyl-1′-thio-D-
glucopyranoside) was dissolved in dry CH CN (5 mL), stirred, and treated with cinnamic alcohol (33.5 mg, 0.25 mmol) and
3
iodine (64.5 mg, 0.25 mmol). The mixture was stirred and cooled with ice for 1 h and then stirred at room temperature for
7 h. After the reaction was finished the reaction mixture was dissolved in CHCl (20 mL) and washed with water (3 × 100 mL)
3
and saturated Na S O solution (50 mL) and again with water (100 mL). The organic layer was dried over anhydrous Na SO .
2 2
3
2
4
The solvent was evaporated. The resulting product was separated over a column of silica gel using toluene:ethylacetate (9:1-
4:1), yield 34.8 mg (30% of theoretical).
Rosavin (1). A solution of protected glycoside (186 mg, 0.4 mmol) in anhydrous methanol (25 mL) was treated with
clean Na (10 mg, 0.4 mmol) dissolved in methanol (25 mL), stirred at room temperature for 5 h, and neutralized by adding
cation-exchanger KU-2 (1 g) in the H-form [8]. Yield of 1, 113 mg (95%).
13
C NMR spectrum (ppm): 136.7, 126.3, 127.4, 128.5, 131.5, 127.5, 70.5, 102.3, 103.5, 64.8-74.5.
PMR spectrum (ppm, J/Hz): 7.45 d, 7.34 t, 6.35 m, 3.17 d, 6 (d, J = 16), 7.25 t, 4.3 (dd, J = 7), 3.3 (t, C-2′), 3.15 (t,
C-3′), 3.05 (t, C-4′), 3.37 (q, C-5′), 3.05 (t, C-6′), 3.35 (t, C-2″), 3.15 (t, C-3″), 3.95 (dd, C-4″), 3.35 (m, C-5″).
398