Chemoenzymatic synthesis of rhodiooctanoside isolated from Chinese medicines, rhodiolae radix

Article abstract of DOI:10.1016/j.tetasy.2004.03.046

Direct β-glucosidation between 1,8-octanediol 5 and D-glucose 6 using the immobilized β-glucosidase (EC 3.2.1.21) from almonds with the synthetic prepolymer ENTP-4000 gave mono-β-glucoside 3 in 58% yield, which was converted into n-octyl β-D-glucopyranoside 2 by means of a chemoenzymatic method. The coupling of n-octyl β-D-glucopyranoside congener 15 and 2,3,4-tri-O-acetyl-α-L-arabinopyranosyl bromide 17, followed by deprotection afforded the synthetic rhodiooctanoside 1, which was identical with natural 1 with respect to the spectral data and specific rotation.

Full text of DOI:10.1016/j.tetasy.2004.03.046

Tetrahedron:
Asymmetry
Tetrahedron: Asymmetry 15 (2004) 1623–1629
Chemoenzymatic synthesis of rhodiooctanoside isolated from
Chinese medicines, rhodiolae radix
Hiroyuki Akita,a,* Eiji Kawaharaa,b and Keisuke Katoa
aSchool of Pharmaceutical Sciences, Toho University, 2-2-1, Miyama, Funabashi, Chiba 274-8510, Japan
bTsukuba Research Institute, Novartis Pharm K.K., 8, Ohkubo, Tsukuba-shi, Ibaraki 300-2611, Japan
Received 12 March 2004; accepted 30 March 2004
Available online
Abstract—Direct b-glucosidation between 1,8-octanediol 5 and
almonds with the synthetic prepolymer ENTP-4000 gave mono-b-glucoside 3 in 58% yield, which was converted into n-octyl b-
glucopyranoside 2 by means of a chemoenzymatic method. The coupling of n-octyl b- -glucopyranoside congener 15 and 2,3,4-tri-
O-acetyl-a- -arabinopyranosyl bromide 17, followed by deprotection afforded the synthetic rhodiooctanoside 1, which was identical
D
-glucose 6 using the immobilized b-glucosidase (EC 3.2.1.21) from
D
-
D
L
with natural 1 with respect to the spectral data and specific rotation.
ꢀ 2004 Elsevier Ltd. All rights reserved.
1. Introduction
b-galactosidase is also reported.5 Herein, we report the
total synthesis of rhodiooctanoside 1 based on the
The Chinese natural medicine ‘Si Lie Hong Jing Tian’
prepared from the roots of Rhodiola (R.) quadrifida
(Pall.) Fisch. et Mey., has been prescribed for hemo-
static, antibechic, and tonic purposes in Chinese tradi-
tional preparations and used as an endermic liniment for
burns and contusions. Rhodiooctanoside 1 was isolated
as one of the chemical constituents of R. quadrifida by
Yoshikawa et al.1a;b and found to show potent hista-
mine release inhibitory activity.1c The structure of 1 was
selective b-glycosidation between the nonprotected
D-
glucose 6 and primary alcohols, such as 1-octanol 4 and
1,8-octanediol 5, catalyzed by the immobilized b-glu-
cosidase (EC 3.2.1.21) from almonds. Retrosyntheti-
cally, the synthesis of 1 can be achieved by the coupling
reaction of the protected n-octyl b-D-glucopyranoside
congener and the protected a- -arabinopyranoside
L
congener. The former can be derived from the b-gluco-
sides 2 and/or 3, which could be obtained by selective b-
glucosidation between D-glucose 6 and 1-octanol 4 and/
determined to be octyl a-
-glucopyranoside by spectroscopic analysis and
chemical degradation studies.1a;b Meanwhile, n-octyl b-
L
-arabinopyranosyl(1 ! 6)-b-
D
or 1,8-octanediol 5, respectively (Scheme 1).
D
-glucopyranoside 2 was isolated from the methan-
olic extract of the roots of Rhodiola sachalinensis,2 which
is a nonionic detergent that is effective for protein
solubilization studies.3 For the enzymatic synthesis of b-
2. Enzymatic b-glycosidation
We have reported previously that the reaction of p-
nitrophenyl b-D-glucopyranoside 7 and 1-octanol 4 and/
or 1,8-octanediol 5 in the presence of commercially
available b-glucosidase (EC 3.2.1.21) from almonds
affords the b-D-glucopyranosides 2 (2% yield) and/or 3
(25% yield), respectively, via a kinetically controlled
procedure. 1,8-Octanediol 5 was found to be better as an
acceptor than 1-octanol 4.6 On the other hand, there are
two approaches for optimizing the product yield from a
given glucosidase in enzymatic glucoside synthesis, that
is the use of either a high donor or high acceptor con-
centration.7 High concentration of both is usually
impractical due to solubility limitations. High donor
D
-glucopyranoside congeners, direct b-glycosidation
between 1,6-hexanediol and
D
-glucose using b-glucosi-
dase (EC 3.2.1.21) from almonds by Vic and Crout4
shows promise, but the substrate used and the reaction
conditions are limited. On the other hand, enzymatic
synthesis of x-hydroxyalkyl and n-alkyl b-galactopyr-
anosides by the transglycosylation reaction using
* Corresponding author. Tel.: +81-0474-72-1805; fax: +81-0474-76-
6195; e-mail: akita@phar.toho-u.ac.jp
0957-4166/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2004.03.046

1624
H. Akita et al. / Tetrahedron: Asymmetry 15 (2004) 1623–1629
HO
R2
4
5
R2 = H
R2 = OH
R1OH2C
HO
HO
O
+
O
HOH2C
R2
O
OH
HO
HO
OH
OR3
NO2
O
OH
Rhodiooctanoside
1
R1
=
R2 = H
6
7
R3 = H
R3
HO
OH
1 = H
=
n-Octyl β-D-glucopyranoside
2
R
R
2 = H
R2 = OH
8-Hydroxyoctyl β-D-glucopyranoside
3
R1 = H
Scheme 1.
Me
Me
Me
Me
CH2NHCOO(CH2)2OCOCH=CH2
Me
CH2=CHCOO(CH2)2OCONHCH2
Me
NHCOO-(CHCH2O)n-CONH
ENTP-4000
Me
HOH2C
HOH2C
HO
HO
O
O
immobilized β-glucosidase
HO
HO
O
NO2
with ENTP-4000
O
OH
PhCH2OH
OH
8
p-Nitrophenyl β-D-glucopyranoside
7
Scheme 2.
concentration is only practical if the donor is inexpen-
sive such as -glucose. High acceptor concentration is
From the above-mentioned background, direct b-glu-
cosidation between -glucose 6 and 1-octanol 4 and/or
D
D
practical if the acceptor is inexpensive or can be recov-
ered from the reaction mixture. Meanwhile, we also
reported that the immobilized enzyme, prepared with b-
glucosidase and synthetic prepolymer ENTP-4000,8
catalyzed the b-glucosidation between 7 and benzyl
1,8-octanediol 5 using native b-glucosidase as well as the
immobilized enzyme was carried out under the reverse
hydrolysis procedure (a thermodynamic controlled
procedure) with the results shown in Table 1. Immobi-
lization of b-D-glucosidase from almonds on a photo-
cross-linkable resin prepolymer (ENTP-4000) was
carried out by the reported procedure.9
alcohol to give benzyl b-
D
-glucopyranoside 8 in mod-
erate yield (14.5%) in a phosphate buffer (Scheme 2).9
Table 1
HOH2C
HOH2C
O
O
R3OH / H2O
HO
HO
HO
OR3
HO
β-glucosidase (250 U)
OH
OH
OH
50 ˚C
2
3
R 3 = Me(CH2)6CH2-
D-glucose 6 (1.1 g )
R 3 = HO(CH2)8-
Entry
R3OH (g)
b-Glucosidase
Time
Product 2 or 3, yield (%)
1
Me(CH2)7OH 4 (14.9)
Me(CH2)7OH 4 (14.9)
Me(CH2)7OH 4 (14.9)
HO(CH2)8OH 5 (3.6)
HO(CH2)8OH 5 (3.6)
HO(CH2)8OH 5 (18.0)
HO(CH2)8OH 5 (18.0)
HO(CH2)8OH 5 (18.0)
Native
A
4
4
4
7
7
6
6
6
2 (5.0)
2 (4.9)
2 (8.2)
2
3a
4b
5c
6
Recovered A
A
3 (19.4)
3 (16.4)
3 (31.2)
3 (58.0)
3 (43.0)
Recovered A
Native
7
8d
A
Recovered A
A: immobilized b-glucosidase with ENTP-4000.
a The same immobilized enzyme in entry 2 was employed again after filtration.
b tert-BuOH (27 mL) was employed as additional solvent.
c The same immobilized enzyme in entry 4 was employed again after filtration.
d The same immobilized enzyme in entry 7 was employed again after filtration.

H. Akita et al. / Tetrahedron: Asymmetry 15 (2004) 1623–1629
1625
By applying the reported procedure,4 when a large
amount of 1-octanol 4 (18.7 equiv) was used as an
Acetylation of 3 gave quantitatively pentaacetate 9,
which was treated with lipase Amano P from Pseudo-
monas sp. to provide mono-alcohol 10 in 80% yield
along with the starting material 9. In this enzymatic
hydrolysis, the terminal acetyl group on the side chain
was selectively hydrolyzed while other acetyl groups on
the sugar part were left intact. Treatment of 10 with
iodine (I2) in the presence of triphenylphosphine (Ph3P)
gave quantitatively the corresponding iodide 11, which
was subjected to reduction with NaBH4 to give tetra-
acetate 12 in 92% yield. Finally, treatment of 12 with
K2CO3 in MeOH provided the desired b-glucoside 2 in
89% yield. Consequently, the overall yield (38% yield) of
acceptor for
or the immobilized b-glucosidase, a low yield of n-octyl
b- -glucopyranoside 2 (entry 1; 5.0% yield, entry 2; 4.9%
D
-glucose 6 in the presence of b-glucosidase
D
yield) was obtained. When the same b-glucosidation was
carried out using the recovered immobilized enzyme, the
yield of 2 was somewhat better than with the use of
native enzyme (entry 3). When 4.0 equiv of 1,8-octandiol
5 was subjected to b-glucosidation using the immobilized
b-glucosidase and the recovered immobilized enzyme in a
co-solvent system [tBuOH/H2O ¼ 9:1 (v/v)],8 moderate
yields (entry 4; 19.4% yield, entry 5: 16.4% yield) of 8-
hydroxyoctyl b-
D
-glucopyranoside 3 were obtained.
2 from D-glucose 6 via six steps is considerably im-
proved upon in comparison to that (5.0–8.2% yield) by
direct b-glucosidation of 1-octanol 4 (Scheme 3).
When a large amount of 1,8-octanediol 5 (20.2 equiv)
was employed for b-glucosidation using the native
enzyme and the immobilized enzyme, the yield of 3 was
considerably improved (entry 6; 31.2% yield, entry 7;
58.0% yield). The recovered enzyme was also found to be
effective (entry 8; 43.0% yield).
Tritylation of 2 gave trityl ether 13 (50% yield) along
with starting material 2 (50% recovery). Acetylation of
13 afforded quantitatively acetate 14, which was sub-
jected to hydrogenolysis in the presence of 20% Pd–C to
provide a mixture (92% yield) of the desired 15 and 16
(15:16 ¼ 3:1). Reaction of this mixture and 2,3,4-tri-O-
3. Synthesis of rodiooctanoside 1
acetyl-a-L
-arabinopyranosyl bromide 1710 in the pres-
ence of silver triflate (AgOTf) and tetramethylurea
(TMU) gave coupled product 18 in 50% yield. Finally,
The conversion of 3 into the desired b-glucoside 2 was
carried out by means of a chemoenzymatic method.
R1OH2C
O
R4O
O
R4O
R2
OR4
R1 = H, R2 = OH, R4 = H
3
9
a
a; Ac2O / pyridine
R1 =Ac, R2 = OAc, R4 = Ac
b
c
d
b; lipase "Amano P" / H2O saturated i-Pr2O
c; Ph3P / I2 / imidazole
R1 = Ac, R2 = OH, R4 = Ac 10
R1 = Ac, R2 = I, R4 = Ac 11
d; NaBH4 / DMSO
R1 =Ac, R2 = H, R4 = Ac
12
2
e
e; K2CO3 / MeOH
f; TrCl / pyridine
R1 = H, R2 = H, R4 = H
f
R1OH2C
O
R4O
O
Me
R4O
OR4
R1 = Tr, R4 = H 13
R1 = Tr, R4 = Ac 14
R1 = H, R4 = Ac 15
g; H2 / 20% Pd-C / MeOH
a
g
AcOH2C
HO
AcO
O
O
+
Me
OAc
16
OAc
OR5
O
/ AgOTf / TMU
h
h;
O
AcO
Br
OAc
O
R5O
17
OR5
O
R4O
R4O
O
Me
OR4
R4 = Ac, R5 = Ac 18
R4 = H, R5 = H
e
1
Scheme 3.

1626
H. Akita et al. / Tetrahedron: Asymmetry 15 (2004) 1623–1629
treatment of 18 with K2CO3 in MeOH provided quan-
titatively the synthetic rhodiooctanoside 1. The spectral
data (1H and 13C NMR) and specific rotation
sidase 100 mg (250 unit) was incubated for 4 d at 50 ꢁC.
The reaction mixture was directly chromatographed on
silica gel (35 g) to give 1-octanol (12.0 g, 80% recovery)
from CHCl3 eluent and b-glucoside 2 (89.2 mg, 5.0%
{½aꢀ ¼ ꢁ28:8 (MeOH)} of synthetic 1 were identical
D
with those {1H and 13C NMR and ½aꢀ ¼ ꢁ29:2
yield) as colorless crystals from CHCl3/MeOH ¼ 10:1
D
27
eluent. 2: ½aꢀ ¼ ꢁ39:8 (c 0.58, H2O); IR (KBr): 3412,
(MeOH)} of natural product 1.
D
2928, 1078, 1036 cmꢁ1
,
1H NMR (MeOH-d4): d 4.24
(1H, d, J ¼ 7:7 Hz), 3.92–3.84 (2H, m), 3.66 (1H, dd,
J ¼ 5:2, 12.0 Hz), 3.59–3.50 (1H, m), 3.37–3.23 (3H, m),
3.17 (1H, dd, J ¼ 7:7, 9.2 Hz), 1.65–1.58 (2H, m), 1.36–
1.30 (10H, m), 0.90 (3H, t, J ¼ 7:2 Hz); 13C NMR
(MeOH-d4): d 104.4 (d), 78.1 (d), 77.9 (d), 75.1 (d), 71.7
(d), 70.9 (t), 62.8 (t), 33.0 (t), 30.8 (t), 30.6 (t), 30.4 (t),
27.1 (t), 23.7 (t), 14.4 (q); FAB MS m=z: 293 (M+1)þ;
Anal. Calcd for C14H28O6: C, 57.51; H, 9.65. Found: C,
57.37; H, 9.71.
4. Conclusion
In conclusion, direct b-glucosidation between 1,8-oc-
tanediol 5 and -glucose 6 using the immobilized b-
glucosidase from almonds with the synthetic prepolymer
D
ENTP-4000 gave mono-b-glucoside 3 in 58% yield,
which was converted into the n-octyl b-
side 2 by means of a chemoenzymatic method. The
coupling of n-octyl b- -glucopyranoside congener 15
and 2,3,4-tri-O-acetyl-a- -arabinopyranosyl bromide
D-glucopyrano-
D
L
5.2.1.2. A mixture of D-glucose 6 (1.1 g, 6.1 mmol), 1-
17, followed by deprotection afforded the synthetic
rhodiooctanoside 1, which was consistent with natural 1
with respect to the spectral data and specific rotation.
octanol (14.9 g, 114.3 mmol), H2O (2 mL), and the
mentioned immobilized b-glucosidase was incubated for
4 d at 50 ꢁC. The reaction mixture was filtered off and
the filtrate directly chromatographed on silica gel (35 g)
to give 1-octanol (12.5 g, 84% recovery) from CHCl3
eluent and b-glucoside 2 (86.6 mg, 4.9% yield) as color-
less crystals from CHCl3/MeOH ¼ 10:1 eluent.
5. Experimental
1H and 13C NMR spectra were recorded on a JEOL EX
400 spectrometer (Tokyo, Japan). Spectral data were
taken with 5–10% (w/v) solution in CDCl3 with Me4Si as
an internal reference. Melting points were determined
on a Yanaco MP-3S micro melting point apparatus and
are uncorrected. Optical rotations were measured on a
JASCO DIP-370 digital polarimeter. The FAB mass
spectra were obtained with a JEOL JMS-AX 500 (ma-
trix; glycerol) spectrometer. IR spectra were recorded on
a JASCO FT/IR-300 spectrometer. All evaporations
were performed under reduced pressure. For column
chromatography, silica gel (Kieselgel 60) was employed.
5.2.1.3. A mixture of D-glucose 6 (1.1 g, 6.1 mmol), 1-
octanol (14.9 g, 114.3 mmol), H2O (2 mL), and the
recovered immobilized b-glucosidase was incubated for
4 d at 50 ꢁC. The reaction mixture was filtered off and
the filtrate directly chromatographed on silica gel (35 g)
to give 1-octanol (12.1 g, 81% recovery) from CHCl3
eluent and b-glucoside 2 (144.4 mg, 8.2% yield) as col-
orless crystals from CHCl3/MeOH ¼ 10:1 eluent.
5.2.2. Synthesis of 8-hydroxyoctyl b-
D-glucopyranoside 3
5.2.2.1. A mixture of D-glucose 6 (1.1 g, 6.1 mmol),
1,8-octanediol (3.6 g, 24.4 mmol), t-BuOH (27 mL), H2O
(3 mL), and the mentioned immobilized b-glucosidase
was incubated for 7 d at 50 ꢁC. The reaction mixture was
filtered off and the filtrate directly chromatographed on
silica gel (150 g) to give 1,8-octanediol (3.2 g, 90%
recovery) from CHCl3/MeOH ¼ 20:1 eluent and b-glu-
coside 3 (365.2 mg, 19.4% yield) as colorless crystals
5.1. Immobilization of b-D-glucosidase using prepolymer
b-
chased from Sigma Chemical Co (G-0395, 2.5–3.6 U/
mg). Immobilization of b- -glucosidase from almonds
D-Glucosidase (EC 3.2.1.21) from almonds was pur-
D
on photocross-linkable resin prepolymer (ENTP-4000)
was carried out by the following procedure. One gram of
ENTP-4000 was mixed with 10 mg of a photosensitizer,
from CHCl3/MeOH ¼ 9:1 eluent. 3: mp 126–128 ꢁC;
29
½aꢀ ¼ ꢁ28:4 (c 0.43, MeOH); IR (KBr): 3419, 3236,
benzoin ethyl ether, and 110 mg of b-D-glucosidase from
D
2925, 1371, 1030 cmꢁ1, 1H NMR (D2O+acetone): d 4.30
(1H, d, J ¼ 8:0 Hz), 3.80–3.75 (2H, m), 3.60–3.50 (2H,
m), 3.45 (2H, t, J ¼ 6:6 Hz), 3.34 (1H, t, J ¼ 9:0 Hz),
3.31–3.28 (1H, m), 3.23 (1H, t, J ¼ 9:4 Hz), 3.11 (1H, t,
J ¼ 8:6 Hz), 1.51–1.37 (4H, m), 1.24–1.14 (8H, m); 13C
NMR (D2O+acetone): d 103.0 (d), 76.7 (d), 76.7 (d),
74.0 (d), 71.5 (d), 70.5 (t), 62.7 (t), 61.6 (t), 32.1 (t), 29.6
(t), 29.3 (t), 29.3 (t), 25.8 (t), 25.8 (t); FAB MS m=z: 309
(M+1)þ; Anal. Calcd for C14H28O7: C, 54.53; H, 9.15.
Found: C, 54.34; H, 9.24.
almonds (3.4 units/mg). The mixture was layered on a
sheet of transparent polyester film (thickness, ca.
0.5 mm). The layer was covered with the transparent
thin film and then illuminated with chemical lamps
(wavelength range, 300–400 nm) for 3 min. The gel film
thus obtained was cut into small pieces (0.5 · 5 · 5 mm)
and used for the bioconversion reaction.
5.2. Enzymatic transglycosylation
5.2.1. Synthesis of n-octyl b-D-glucopyranoside 2
5.2.2.2. A mixture of
D-glucose 6 (1.1 g, 6.1 mmol),
1,8-octanediol (3.6 g, 24.4 mmol), tert-BuOH (27 mL),
H2O (3 mL), and the recovered immobilized b-glucosi-
dase was incubated for 7 d at 50 ꢁC. The reaction mix-
5.2.1.1. A mixture of D-glucose 6 (1.1 g, 6.1 mmol), 1-
octanol (14.9 g, 114.3 mmol), H2O (2 mL), and b-gluco-

H. Akita et al. / Tetrahedron: Asymmetry 15 (2004) 1623–1629
1627
ture was filtered off and the filtrate directly chromato-
graphed on silica gel (150 g) to give 1,8-octanediol (3.1 g,
86% recovery) from CHCl3/MeOH ¼ 20:1 eluent and b-
glucoside 3 (280.6 mg, 16.4% yield) as colorless crystals
from CHCl3/MeOH ¼ 9:1 eluent.
5.3.2. A suspension of 9 (100 mg, 0.193 mmol), lipase
Amano P (100 mg) in H2O saturated i-Pr2O (17 mL) was
incubated for 22 h at 33 ꢁC. The reaction mixture was
filtered with the aid of Celite and the filtrate then
evaporated to give a residue. This was chromatographed
on silica gel (15 g) to afford 9 (20 mg, 20% recovery)
from n-hexane/AcOEt (2:1) eluent and 10 (74 mg, 80%
5.2.2.3. A mixture of
D-glucose 6 (1.1 g, 6.1 mmol),
yield) as a colorless syrup from n-hexane/AcOEt (1:1)
1,8-octanediol (18 g, 123.1 mmol), H2O (2 mL), and b-
glucosidase 100 mg (250 unit) was incubated for 7 d at
50 ꢁC. The reaction mixture was directly chromato-
graphed on silica gel (35 g) to give 1,8-octanediol (17.2 g,
95% recovery) from CHCl3/MeOH ¼ 20:1 eluent and b-
glucoside 3 (587.0 mg, 31.2% yield) as colorless crystals
from CHCl3/MeOH ¼ 9:1 eluent.
25
D
eluent. 10: ½aꢀ ¼ ꢁ20:6 (c 0.67, CHCl3); IR (KBr):
3564, 1752 cmꢁ1
,
1H NMR (CDCl3): d 5.20 (1H, t,
J ¼ 9:6 Hz), 5.08 (1H, t, J ¼ 9:6 Hz), 4.98 (1H, dd,
J ¼ 8:3, 9.3 Hz), 4.49 (1H, d, J ¼ 8:3 Hz), 4.26 (1H, dd,
J ¼ 4:9, 11.5 Hz), 4.14 (1H, dd, J ¼ 5:4, 11.5 Hz), 3.87
(1H, dt, J ¼ 6:4, 9.6 Hz), 3.71–3.67 (1H, m), 3.63 (2H, t,
J ¼ 6:4 Hz), 3.47 (1H, dt, J ¼ 6:8, 9.3 Hz), 2.09 (3H, s),
2.04 (3H, s), 2.03 (3H, s), 2.01 (3H, s), 1.59–1.52 (4H,
m), 1.46–1.28 (8H, m); 13C NMR (CDCl3): d 170.7 (s),
170.4 (s), 169.4 (s), 169.3 (s), 100.8 (d), 72.9 (d), 71.7 (d),
71.4 (d), 70.2 (t), 68.5 (d), 62.9 (t), 62.0 (t), 32.7 (t), 29.3
(t), 29.3 (t), 29.2 (t), 25.7 (t), 25.6 (t), 20.7 (q), 20.6 (q),
20.6 (q), 20.6 (q); FAB MS m=z: 515 (M+K)þ. Anal.
Calcd for C22H36O11: C, 55.45; H, 7.62. Found: C, 55.06;
H, 7.77.
5.2.2.4. A mixture of
D-glucose 6 (1.1 g, 6.1 mmol),
1,8-octanediol (18 g, 123.1 mmol), H2O (2 mL), and the
mentioned immobilized b-glucosidase was incubated for
6 d at 50 ꢁC. The reaction mixture was filtered off and
the filtrate directly chromatographed on silica gel (35 g)
to give 1,8-octanediol (17.1 g, 95% recovery) from
CHCl3/MeOH ¼ 20:1 eluent and b-glucoside 3 (1.09 g,
58.0% yield) as colorless crystals from CHCl3/
MeOH ¼ 10:1 eluent.
5.3.3. A mixture of 10 (148 mg, 0.31 mmol), Ph3P
(173 mg, 0.66 mmol), imidazole (45 mg, 0.66 mmol), and
I2 (151 mg, 0.59 mmol) in THF (2.5 mL) was stirred for
30 min at room temperature. The reaction mixture was
diluted with H2O and extracted with AcOEt. The
organic layer was dried over MgSO4 and evaporated to
give a residue. This was chromatographed on silica gel
5.2.2.5. A mixture of
D-glucose 6 (1.1 g, 6.1 mmol),
1,8-octanediol (18 g, 123.1 mmol), H2O (2 mL), and the
recovered immobilized b-glucosidase was incubated for
6 d at 50 ꢁC. The reaction mixture was filtered off and
the filtrate directly chromatographed on silica gel (35 g)
to give 1,8-octanediol (17.0 g, 94% recovery) from
CHCl3/MeOH ¼ 20:1 eluent and b-glucoside 3 (808 mg,
43.0% yield) as colorless crystals from CHCl3/
MeOH ¼ 10:1 eluent.
[10 g, n-hexane/AcOEt (3:1)] to afford 11 (182 mg,
26
D
quantitative yield) as a colorless oil. 11: ½aꢀ ¼ ꢁ16:0 (c
1
0.35, CHCl3); IR (KBr): 1751 cmꢁ1, H NMR (CDCl3):
d 5.20 (1H, t, J ¼ 9:6 Hz), 5.08 (1H, t, J ¼ 10:0 Hz), 4.98
(1H, t, J ¼ 8:0 Hz), 4.49 (1H, d, J ¼ 8:0 Hz), 4.27
(1H, dd, J ¼ 4:4, 12.0 Hz), 4.16–4.12 (1H, m), 3.87 (1H,
dt, J ¼ 6:0, 9.6 Hz), 3.71–3.67 (1H, m), 3.48 (1H,
dt, J ¼ 6:4, 9.6 Hz), 3.18 (2H, t, J ¼ 8:0 Hz), 2.09
(3H, s), 2.04 (3H, s), 2.03 (3H, s), 2.01 (3H, s),
1.85–1.53 (6H, m), 1.44–1.24 (6H, m); FAB MS m=z: 625
(M+K)þ.
5.3. Conversion of 3 into n-octyl b-D-glucopyranoside 2
5.3.1. A mixture of 3 (300 mg, 0.97 mmol), Ac2O
(795 mg, 7.8 mmol), 4-dimethylaminopyridine (DMAP;
10 mg, 0.08 mmol) in pyridine (1 mL, 12.4 mmol) was
stirred for 1 h at room temperature. The reaction mix-
ture was diluted with H2O and extracted with AcOEt.
The organic layer was washed with 10% aqueous HCl,
7% aqueous NaHCO3, and brine. The organic layer was
dried over MgSO4 and evaporated to give a residue,
which was chromatographed on silica gel [15 g, n-hex-
5.3.4. A mixture of 11 (921 mg, 1.57 mmol) and NaBH4
(120 mg, 3.16 mmol) in DMSO (15 mL) was stirred for
1 h at room temperature. The reaction mixture was di-
luted with H2O and extracted with AcOEt. The organic
layer was dried over MgSO4 and evaporated to give a
residue. This was chromatographed on silica gel [15 g,
ane/AcOEt (2:1)] to afford 9 (504 mg, quantitative yield)
22
D
as a colorless syrup. 9: ½aꢀ ¼ ꢁ17:4 (c 0.61, CHCl3); IR
(KBr): 1752 cmꢁ1
,
1H NMR (CDCl3): d 5.20 (1H, t,
J ¼ 9:6 Hz), 5.08 (1H, t, J ¼ 9:6 Hz), 4.98 (1H, t,
J ¼ 8:8 Hz), 4.49 (1H, d, J ¼ 8 Hz), 4.27 (1H, dd,
J ¼ 4:8, 12.4 Hz), 4.14 (1H, dd, J ¼ 2:4, 12.4 Hz), 4.05
(2H, t, J ¼ 6:8 Hz), 3.87 (1H, dt, J ¼ 6:4, 9.6 Hz), 3.69
(1H, ddd, J ¼ 2:4, 4.8, 9.6 Hz), 3.47 (1H, dt, J ¼ 6:8,
9.6 Hz), 2.08 (3H, s), 2.04 (3H, s), 2.04 (3H, s), 2.02 (3H,
s), 2.01 (3H, s), 1.63–1.54 (4H, m), 1.35–1.25 (8H, m);
13C NMR (CDCl3): d 171.2 (s), 170.7 (s), 170.3 (s), 169.4
(s), 169.3 (s), 100.8 (d), 77.3 (d), 72.9 (d), 71.8 (d), 71.4
(d), 70.2 (t), 68.5 (d), 64.6 (t), 62.0 (t), 29.4 (t), 29.2 (t),
29.2 (t), 28.6 (t), 25.8 (t), 25.7 (t), 21.0 (q), 20.7 (q), 20.7
(q), 20.6 (q), 20.6 (q); FAB MS m=z: 541 (M+Na)þ, 519
(M+H)þ.
n-hexane/AcOEt (1:1)] to afford 12 (670 mg, 92 yield) as
27
D
a colorless needle. 12: mp 58–60 ꢁC; ½aꢀ ¼ ꢁ20:2 (c
1
0.59, CHCl3); IR (KBr): 1755 cmꢁ1, H NMR (CDCl3):
5.20 (1H, t, J ¼ 9:3 Hz), 5.08 (1H, t, J ¼ 9:8 Hz), 4.98
(1H, dd, J ¼ 7:8, 9.3 Hz), 4.49 (1H, d, J ¼ 7:8 Hz), 4.26
(1H, dd, J ¼ 4:9, 12.2 Hz), 4.14 (1H, dd, J ¼ 2:0,
12.2 Hz), 3.87 (1H, dt, J ¼ 6:3, 9.3 Hz), 3.69 (1H, ddd,
J ¼ 2:4, 4.4, 9.8 Hz), 3.47 (1H, dt, J ¼ 6:8, 9.8 Hz), 2.08
(3H, s), 2.04 (3H, s), 2.02 (3H, s), 2.00 (3H, s), 1.63–1.49
(4H, m), 1.34–1.22 (8H, m), 0.88 (3H, t, J ¼ 6:4 Hz); 13C
NMR (CDCl3): d 170.7 (s), 170.3 (s), 169.4 (s), 169.3 (s),
100.9 (d), 72.9 (d), 71.8 (d), 71.4 (d), 70.3 (t), 68.5 (d),

1628
H. Akita et al. / Tetrahedron: Asymmetry 15 (2004) 1623–1629
62.1 (t), 31.8 (t), 29.4 (t), 29.3 (t), 29.3 (t), 25.8 (t), 22.6
(t), 20.7 (q), 20.6 (q), 20.6 (q), 20.6 (d), 14.1 (q); FAB
MS m=z: 499 (M+K)þ.
(M+K)þ. Anal. Calcd for C39H48O9+H2O: C, 69.00; H,
7.42. Found: C, 69.21; H, 7.17.
5.3.5. A mixture of 12 (1.41 g, 3.07 mmol) and K2CO3
(412 mg, 3.0 mmol) in MeOH (20 mL) was stirred for
25 min at room temperature. The reaction mixture was
evaporated to give a residue, which was chromato-
graphed on silica gel [15 g, CHCl3/MeOH (9:1)] to afford
5.4.3. A mixture of 14 (650 mg, 0.98 mmol) and 20% Pd–
C (148 mg) in MeOH (20 mL) was subjected to catalytic
hydrogenolysis at ambient temperature and the reaction
mixture filtered with the aid of Celite to give the filtrate.
Evaporation of the filtrate gave a residue, which was
chromatographed on silica gel [10 g, n-hexane/AcOEt
2 (796 mg, 89 yield) as a colorless amorphas. 1H and 13
C
NMR spectra of the present 2 were identical with those
of enzymatic b-glucoside 2.
(2:1)] to give a mixture 15:16 (3:1; 381 mg, 92% yield) as
27
a colorless syrup. 15 and 16: ½aꢀ ¼ ꢁ32:5 (c 0.63,
D
CHCl3); IR (KBr): 3429, 1753 cmꢁ1, FAB MS m=z: 457
(M+K)þ. Anal. Calcd for C20H34O9: C, 57.40; H, 8.19.
Found: C, 57.09; H, 8.24. 15: 1H NMR (CDCl3): d 5.25
(1H, t, J ¼ 9:6 Hz), 5.03 (1H, t, J ¼ 9:6 Hz), 4.96 (1H,
dd, J ¼ 8:0, 9.6 Hz), 4.52 (1H, d, J ¼ 8:0 Hz), 3.90–3.85
(1H, m), 3.77–3.72 (1H, m), 3.64–3.45 (3H, m), 2.05 (3H,
s), 2.04 (3H, s), 2.01 (3H, s), 1.58–1.54 (2H, m), 1.32–
1.22 (10H, m), 0.88 (3H, t, J ¼ 6:4 Hz); 13C NMR
(CDCl3): d 170.3 (s), 170.0 (s), 169.3 (s), 100.8 (d), 73.4
(d), 72.7 (d), 71.5 (d), 70.2 (t), 68.8 (d), 61.3 (t), 31.7 (t),
29.4 (t), 29.2 (t), 29.2 (t), 25.8 (t), 22.6 (t), 20.8 (q), 20.6
(q), 20.6 (q), 14.0 (q).
5.4. Conversion of 2 into n-octyl b-D-glucopyranoside
congener 15
5.4.1. A mixture of 2 (642 mg, 2.2 mmol) and TrCl
(667 mg, 2.4 mmol) in pyridine (1 mL, 12.4 mmol) was
stirred for 24 h at room temperature. The reaction
mixture was diluted with toluene (100 mL) and evapo-
rated under reduced pressure to give a residue, which
was chromatographed on silica gel (15 g) to afford 13
(588 mg, 50% yield) as a colorless syrup from CHCl3/
MeOH (50:1) eluent and starting material 2 (321 mg,
50% recovery) from CHCl3/MeOH (10:1) eluent. 13:
27
1
½aꢀ ¼ ꢁ45:2 (c 0.63, CHCl3); IR (KBr): 3396 cmꢁ1, H
D
NMR (CDCl3): d 7.45 (6H, d, J ¼ 6:8 Hz), 7.30–7.19
(9H, m), 4.25 (1H, d, J ¼ 9:2 Hz), 3.88 (1H, dt, J ¼ 7:2,
9.2 Hz), 3.56–3.33 (7H, m), 1.67–1.60 (2H, m), 1.35–1.22
(10H, m), 0.86 (3H, t, J ¼ 6:8 Hz); 13C NMR (CDCl3): d
143.7 (s, Ph-4ꢁ), 128.7 (d, Ph-3ꢁ), 127.9 (d, Ph-3ꢁ), 127.1
(d, Ph-3ꢁ), 102.5 (d), 87.0 (s), 76.3 (d), 74.2 (d), 73.6 (d),
71.9 (d), 70.1 (t), 64.3 (t), 31.8 (t), 29.7 (t), 29.4 (t), 29.2
(t), 26.0 (t), 22.6 (t),14.1 (q); FAB MS m=z: 557
(M+Na)þ.
5.5. Rhodiooctanoside 1
5.5.1. To a solution of the above-mentioned mixture 15
and 16 (290 mg, 0.69 mmol), 2,3,4-tri-O-acetyl-a-L-ara-
binopyranosyl bromide 17 (347 mg, 1.02 mmol) and
tetramethyl urea (TMU, 249 mg, 2.15 mmol) in CH2Cl2
(5 mL) was added AgOTf (366 mg, 1.42 mmol) at 0 ꢁC
under argon atmosphere. The whole was covered with
aluminum foil and stirred for 30 min at room tempera-
ture. The reaction mixture was cooled at 0 ꢁC and
quenched with AcOEt (15 mL) and 7% aqueous
NaHCO3 solution (20 mL). The reaction mixture was
extracted with AcOEt and dried over MgSO4. Evapo-
ration of the organic solvent gave a residue, which was
chromatographed on silica gel (20 g) to afford tetraace-
tate 12 (73 mg, 22% yield) from n-hexane/AcOEt (4:1)
eluent, 16 (41 mg, 14% recovery), and 18 (233 mg, 50%
5.4.2. A mixture of 13 (700 mg, 1.31 mmol), Ac2O
(669 mg, 6.55 mmol), 4-dimethylaminopyridine (DMAP;
10 mg, 0.08 mmol) in pyridine (2 mL, 25.3 mmol) was
stirred for 1 h at room temperature. The reaction mix-
ture was diluted with H2O and extracted with AcOEt.
The organic layer was washed with brine and dried over
MgSO4. Evaporation of the organic solvent gave a res-
idue, which was again diluted with toluene and the
whole evaporated to give a residue. This was chroma-
tographed on silica gel [20 g, n-hexane/AcOEt (7:1)] to
yield) as a colorless amorphas from n-hexane/AcOEt
27
(3:1) eluent in elution order. 18: mp 122–123 ꢁC; ½aꢀ
¼
D
1
ꢁ8:5 (c 0.63, CHCl3); IR (KBr): 1746, 1057 cmꢁ1, H
NMR (MeOH-d4): d 5.25–5.19 (2H, m), 5.09–5.07 (2H,
m), 4.98 (1H, t, J ¼ 9:6 Hz), 4.88–4.84 (1H, m), 4.62
(1H, d, J ¼ 8:0 Hz), 4.58–4.56 (1H, m), 4.01–3.84 (3H,
m), 3.80–3.71 (2H, m), 3.60 (1H, dd, J ¼ 4:8, 10.8 Hz),
3.54–3.48 (1H, m), 2.12 (3H, s), 2.08 (3H, s), 2.02 (3H,
s), 2.01 (3H, s), 2.00 (3H, s), 1.96 (3H, s), 1.57–1.53 (2H,
m), 1.35–1.27 (10H, m), 0.90 (3H, t, J ¼ 6:8 Hz); 13C
NMR (CDCl3): d 171.9 (s), 171.7 (s), 171.6 (s), 171.4 (s),
171.2 (s), 171.1 (s), 101.9 (d), 101.7 (d), 74.6 (d), 74.0 (d),
73.0 (d), 71.7 (d), 70.9 (t), 70.5 (d), 70.3 (d), 69.3 (d), 68.4
(t), 64.1 (t), 33.0 (t), 30.6 (t), 30.5 (t), 30.5 (t), 27.1 (t),
23.7 (t), 20.9 (q), 20.8 (q), 20.7 (q), 20.6 (q), 20.6 (q), 20.6
(q), 14.5 (q); FAB MS m=z: 715 (M+K)þ. Anal. Calcd
for C31H48O16: C, 55.02; H, 7.15. Found: C, 55.02; H,
7.20.
afford 14 (865 mg, quantitative yield) as a colorless
27
D
syrup. 14: ½aꢀ ¼ þ21:8 (c 0.51, CHCl3); IR (KBr):
1757 cmꢁ1
,
1H NMR (CDCl3): d 7.45 (6H, d, J ¼
7:3 Hz), 7.40–7.20 (9H, m), 5.17–5.12 (2H, m), 5.07–5.02
(1H, m), 4.50 (1H, d, J ¼ 7:8 Hz), 3.93 (1H, dt, J ¼ 6:3,
9.3 Hz), 3.59–3.53 (2H, m), 3.24 (1H, dd, J ¼ 2:0,
10.6 Hz), 3.10 (1H, dd, J ¼ 4:9, 10.6 Hz), 2.05 (3H, s),
1.99 (3H, s), 1.72 (3H, s), 1.68–1.58 (4H, m), 1.35–1.24
(8H, m), 0.87 (3H, t, J ¼ 6:9 Hz); 13C NMR (CDCl3): d
170.5 (s), 169.4 (s), 169.0 (s), 143.6 (s, Ph-4ꢁ), 128.7 (d,
Ph-3ꢁ), 127.8 (d, Ph-3ꢁ), 127.0 (d, Ph-3ꢁ), 100.8 (d), 86.6
(s), 73.3 (d), 73.2 (d), 71.6 (d), 69.8 (t), 68.9 (d), 62.1 (t),
31.8 (t), 29.5 (t), 29.3 (t), 29.3 (t), 26.0 (t), 22.6 (t), 20.7
(q), 20.7 (q), 20.4 (q), 14.1 (q); FAB MS m=z: 699

H. Akita et al. / Tetrahedron: Asymmetry 15 (2004) 1623–1629
1629
5.5.2. A mixture of 18 (100 mg, 0.148 mmol) and K2CO3
References and notes
(20.4 mg, 0.15 mmol) in MeOH (5 mL) was stirred for
15 min at room temperature. The reaction mixture was
evaporated to give a residue, which was chromato-
graphed on silica gel [6 g, CHCl3/MeOH (5:1–1:1)]
1. (a) Yoshikawa, M.; Shimada, H.; Shimada, H.; Matsuda,
H.; Yamahara, J.; Murakami, N. Chem. Pharm. Bull.
1995, 43, 1245–1247; (b) Yoshikawa, M.; Shimada, H.;
Shimada, H.; Murakami, N.; Yamahara, J.; Matsuda, H.
Chem. Pharm. Bull. 1996, 44, 2086–2091; (c) Yoshikawa,
M.; Shimada, H.; Horikawa, S.; Murakami, T.; Shimada,
H.; Yamahara, J.; Matsuda, H. Chem. Pharm. Bull. 1997,
45, 1498–1503.
to afford 1 (62 mg, quantitative yield) as a colorless
24
D
amorphas. 1: ½aꢀ ¼ ꢁ28:8 (c 0.42, MeOH); IR (KBr):
1
3404, 1055 cmꢁ1, H NMR (MeOH-d4): d 4.31 (1H, d,
J ¼ 6:7 Hz), 4.24 (1H, d, J ¼ 7:6 Hz), 4.08 (1H, dd,
J ¼ 1:8, 11.3 Hz), 3.88–3.81 (3H, m), 3.73 (1H, dd,
J ¼ 5:5, 11.3 Hz), 3.59 (1H, dd, J ¼ 7:0, 8.5 Hz),
3.54–3.50 (3H, m), 3.44–3.41 (1H, m), 3.34–3.29 (2H,
m), 3.19–3.16 (1H, m), 1.63–1.58 (2H, m), 1.48–1.25
(10H, m), 0.89 (3H, t, J ¼ 7:0 Hz); 13C NMR (MeOH-
d4): d 105.1, 104.3, 77.9, 76.7, 75.0, 74.1, 72.3, 71.5, 71.0,
69.4, 69.4, 66.7, 33.0, 30.8, 30.5, 30.4, 27.1, 23.7, 14.4;
High (FAB) MS (matrix; m-nitrobenzylalcohol)
m=z: 447.2195 (M+Na)þ, Calcd for C19H36O10+Na,
447.2206.
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3. (a) Sivaprasadarao, A.; Boudjelal, M.; Findlay, J. B. C.
Biochem. J. 1994, 302, 245–251; (b) Gast, P.; Hemelrijk,
P.; Hoff, A. J. FEBS Lett. 1994, 337, 39–42.
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2513–2516.
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Lett. 1991, 945–948.
6. Kurashima, K.; Fujii, M.; Ida, Y.; Akita, H. Chem.
Pharm. Bull. 2004, 52, 270–275.
7. Stevenson, E.; Stanley, R. A.; Furneaux, R. H. Biotechnol.
Bioeng. 1993, 42, 657–666.
8. Fukui, S.; Tanaka, A. Adv. Biochem. Eng./Biotechnol.
1984, 29, 1–33.
Acknowledgements
The authors are grateful to Prof. Masayuki Yoshikawa,
Kyoto Pharmaceutical University, Japan, for generously
donating the spectral data of natural rhodiooctano-
side 1.
9. Kurashima, K.; Fujii, M.; Ida, Y.; Akita, H. J. Mol. Catal.
B 2004, 26, 87–98.
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