Efficient synthesis of glycyrrhetinic acid glycoside/glucuronide derivatives using silver zeolite as promoter

Article abstract of DOI:10.1016/j.carres.2009.04.015

3-O-Glycopyranosides of glycyrrhetinic acid have been synthesized in good to high yields and excellent stereoselectivity using glycosyl bromide donors and silver zeolite as promoter. In addition to the preparation of glycosides containing β-linked glucosy

Full text of DOI:10.1016/j.carres.2009.04.015

Carbohydrate Research 344 (2009) 1063–1071
Contents lists available at ScienceDirect
Carbohydrate Research
journal homepage: www.elsevier.com/locate/carres
Efficient synthesis of glycyrrhetinic acid glycoside/glucuronide derivatives
using silver zeolite as promoter q
Maria Carmen del Ruiz Ruiz a, Hassan Amer a, Christian Stanetty a, Igor Beseda b, Laszlo Czollner b,
Priti Shah b, Ulrich Jordis a, Bernhard Kueenburg c, Dirk Claßen-Houben c, Andreas Hofinger a, Paul Kosma a,
*
a Department of Chemistry, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria
b Institute of Applied Synthetic Chemistry, Vienna University of Technology, Getreidemarkt 9-163OC, A-1060 Vienna, Austria
c Onepharm Research and Development GmbH, Veterinärplatz 1, A-1220 Vienna, Austria
a r t i c l e i n f o
a b s t r a c t
Article history:
3-O-Glycopyranosides of glycyrrhetinic acid have been synthesized in good to high yields and excellent
stereoselectivity using glycosyl bromide donors and silver zeolite as promoter. In addition to the prepa-
ration of glycosides containing b-linked glucosyl, 2-deoxy-2-trichloroacetamido-glucosyl, galactosyl, cel-
lobiosyl and lactosyl residues, also the deactivated acetylated methyl glucopyranosyluronate bromide
donor could be coupled to triterpene aglycon ester derivatives in good yields. The ester protecting group
located at C-30 of the oleanolic acid scaffold exerted an influence on the overall yield, with the methyl-
ester-protected glycosyl acceptor giving better yields compared to the allyl, benzyl as well as diphenyl-
methyl ester aglycon. The acetyl-protected glucuronides were differently deblocked in high yields via
Zemplén deacetylation or via hydrogenolysis followed by Zemplén deacetylation, and alkaline hydrolysis,
respectively, to allow for a selective liberation of the ester groups from either the glucuronide or the glyc-
yrrhetinic acid unit, respectively. The target glycosides/glucuronides serve as probes for pharmaceutical
studies aimed at defining structure–activity relationships of glycoside/glucuronide triterpenes.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 25 February 2009
Received in revised form 7 April 2009
Accepted 12 April 2009
Available online 20 April 2009
Keywords:
Triterpene
Saponin
Glucuronic acid
Glycyrrhizin
Glycosylation
Silver zeolite
1. Introduction
from low yields in both the coupling and deprotection steps. As
examples, Koenigs–Knorr and Helferich-type reactions of glycosyl
Glycyrrhizin constitutes a major component of the natural
saponins isolated from licorice roots (Glycyrrhiza radix) and has
been used since many centuries in traditional Asian medicines
for treatment of pulmonary and inflammatory diseases. Glycyrrhi-
zin harbors a broad spectrum of bioactivities such as anti-viral,
cytotoxic, endocrine and anti-inflammatory, but also hepatopro-
tective properties, and is being exploited in the treatment of
chronic hepatitis.1,2 The carbohydrate portion of glycyrrhizin com-
prises a b-(1?2)-linked glucuronic acid disaccharide linked to O-3
of the triterpene. Several studies have addressed the modification
of the disaccharide unit as well as the de novo attachment of sugar
residues to the 3-b hydroxy group of the olean-11-oxo-12-ene
scaffold.3,4 The biological results obtained with these compounds
regarding the contribution of the carbohydrate portion towards
biological activities such as haemolytic or anti-viral activities have
been elusive.5,6 Furthermore, previously published glycosylation
reactions of glycyrrhetinic acid acceptor derivatives have suffered
bromide donors have been performed using silver carbonate,7 sil-
9
ver triflate8 or Hg(CN)2/HgBr2 or by employing TMS-bromide
and CoBr2 as promoters in the coupling step with reducing sug-
ars.10 Also condensation of sugar peracetates in the presence of
SnCl4 with a glycyrrhetinic acid aglycon has been reported.10 These
approaches proceeded either in low yields, additional orthoester
formation or with low anomeric selectivity. Also formation of the
corresponding enol-glycosides at position 11 was observed as a
side reaction.11
By contrast, use of trifluoroacetimidate donors proved to be
effective for the coupling of 2-amino-2-deoxy-sugars to allyl ester
protected oleanolic acid.12 Similarly, trichloroacetimidate donors
have been successfully coupled to the 3-OH group of oleanolic acid
and glycyrrhetinic acid in high yields, albeit with concomitant for-
mation of small amounts of the 11-enol glycoside in the latter
case.13,14 Finally, the glucuronide moiety has been formed in most
cases by TEMPO oxidation of suitably protected intermediate glu-
copyranosyl units in a late stage of the synthetic scheme, requiring
additional protecting group manipulation, while direct glycosyla-
tion using glucopyranosyluronate donors proceeded with low
anomeric selectivity.15,16 Within the framework of ongoing inves-
tigations on bioactivities of glycosylated triterpenes, we have
therefore set out to study efficient procedures for the generation
q
This work was supported by ZIT (Zentrum für Innovation and Technologieent-
wicklung,Vienna) within the project Antiviral Spot of Excellence (Aspex).
* Corresponding author. Tel.: +43 1 36006 6055; fax: +43 1 36006 6059.
E-mail address: paul.kosma@boku.ac.at (P. Kosma).
0008-6215/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.carres.2009.04.015

1064
Maria Carmen del Ruiz Ruiz et al. / Carbohydrate Research 344 (2009) 1063–1071
of glycyrrhetinic acid glycosides which should also be applicable to
the synthesis of glucuronide derivatives of glycyrrhetinic acid.
Finally, Koenigs–Knorr conditions were applied in model reac-
tions using the acetylated glucopyranosyl bromide 7, in the pres-
ence of Ag2CO3/I2 (5:1) (Scheme 2). Reaction of 7 with acceptor 4
furnished the orthoester 8 in 51% and the b-glycoside 9 in 29%
yield.19 The structural assignment of the orthoester 8 was based
on the observed high-field shifted signal of the methyl group of
the orthoacetate (d 1.74, endo-CH3).20 Applying a large excess of
donor 7 (6 equiv) and 9:1 Ag2CO3/I2 as promoter afforded the gly-
coside 9 in 60% yield without formation of the orthoester. Eventu-
ally, silver zeolite, which has previously been proven as versatile
promoter for related glycosylation reactions,21–23 proved to be an
efficient alternative and the b-glucopyranoside 9 was isolated in
60% yield. The reaction was performed in dichloromethane in the
presence of molecular sieves 4 Å and using 3 equiv of the bromide
donor 7. The coupling reaction proceeded slowly but in a stereose-
lective fashion, without orthoester formation and with only trace
2. Results and discussion
2.1. Glycosylation of glycyrrhetinic acid derivatives
In order to explore the reactivity of commonly used donors in
the synthesis of glycosylated triterpenes, hepta-O-acetyl cellobiosyl
trichloroacetimidate and bromide donors 1 and 2, respectively,
were used in model reactions with the glycyrrhetinic acid methyl
ester derivative 3 in the presence of various Lewis acid promoters
in dichloromethane (Scheme 1, Table 1). The reactions proceeded
with exclusive formation of the desired b-linked disaccharide deriv-
atives, albeit in poor to modest yields, with TMSOTf as promoter
giving the best result followed by tris(trifluorophenyl)borane
(entries 1 and 2), whereas boron trifluoride etherate as promoter
afforded a very low yield (entry 3).17 When ZnBr2 was used as cat-
alyst, the reaction proceeded in two stages.18 Initially, the triterpen-
e acceptor 3 was consumed and after 2 h at room temperature, a
putative intermediate orthoester could be visualized by thin-layer
chromatography. Eventually the orthoester was converted in poor
yield (13%) into the product 8 upon continued exposure to ZnBr2
(Table 1, entry 4). Next the hepta-O-acetyl cellobiosyl bromide 2
was tested as glycosylating agent for the diphenylmethyl ester
derivative 4 under Helferich conditions (in the presence of 1.5:2
Hg(CN)2/HgBr2), which did not lead to satisfactory results either
(Table 1, entry 5).5a The stereochemistry of the glycosidic linkage
of the glycoside 5 was determined in all cases to be b based on
amounts of a-glycoside being formed. Using these conditions, gly-
cosylation of the methyl ester aglycon 3 afforded the monogluco-
pyranoside derivative 10 in 65% yield (Scheme 2).
Due to the easy set-up and simple work-up of the reaction, a
series of mono- and disaccharide glycoside derivatives could be
prepared (Table 2, entries 1–14, Scheme 3). The cellobiosyl glyco-
sides 5 and 6 could be isolated in substantially better yields (Table
2, entries 1 and 2) compared to the use of the trichloroacetimidate
donor 1 (Table 1, entry 1) or in comparison to the coupling reaction
of the bromide donor 2 under Helferich conditions (Table 1, entry
5). The results were confirmed by similar glycosylation reactions
using glycopyranosyl bromide donors 13–15 and methyl (2,3,4-
tri-O-acetyl-glucopyranosyl bromide)uronate (16). Thus, the b-D-
galactopyranosyl derivatives 17 and 18 were prepared in good
the value of the coupling constant of H-10 (J1 ,2 8.0 Hz).
0
0
OAc
OAc
O
O
AcO
O
AcO
AcO
OAc
AcO
Me
R
Me
Me
O
Me
1 R = OC(=NH)CCl3
2 R = Br
HO
+
Me
Me
OR
Me
O
3 R = Me
R = (Ph)2CH
4
OAc
OAc
Me
Me
Me
O
Me
O
O
AcO
AcO
O
AcO
O
Me
Me
OAc
OR
OAc
Me
5 R = Me
6
R = (Ph)2CH
O
Scheme 1. Glycosylation of glycyrrhetinic acid derivatives with cellobiosyl donors. For conditions and yields see Table 1.
Table 1
Summary of glycosylation reactions using cellobiosyl donors 1 and 2
Entry
Donor
Acceptor
Product
Promoter
Equiv
T (°C)
T (h)
Yield (%)
1
2
3
4
5
1
1
1
1
2
3
3
3
3
4
5
5
5
5
6
TMSOTf
(F5C6)3B
0.1
0.15
0.5
0.7
3.5
ꢀ80
ꢀ40
ꢀ60
40
1
15
2
15
16
43
40
18
13
20
ꢁ
BF3 ꢂEt2O
ZnBr2
Hg(CN)2/HgBr2
20

Maria Carmen del Ruiz Ruiz et al. / Carbohydrate Research 344 (2009) 1063–1071
1065
OAc
Me
Me
Me O
Me
Me
O
AcO
AcO
O
Me
OCH(Ph)2
OAc
Me
Me
9
4
O
+
OAc
a)
OAc
Me
O
AcO
AcO
O
AcO
AcO
AcO
Br
O
O
O
Me
7
Me O
Me
Me
3
+
b)
Me
OCH(Ph)2
Me
8
OAc
Me
O
Me
Me O
Me
Me
O
AcO
AcO
O
Me
OMe
OAc
Me
10
O
Scheme 2. Reagents and conditions: (a) 5:1 Ag2CO3–I2, CH2Cl2, rt, 4 days, 51% for 8, 29% for 9; (b) Ag zeolite, CH2Cl2, molecular sieves 4 Å, rt, 4 days, 65% for 9, 65% for 10.
2.2. Deprotection of glucuronide derivatives
Table 2
Summary of silver zeolite promoted glycosylation reactions
Based on the different ester protecting groups of the glucuro-
nide derivatives 23 and 24, a series of partially as well as fully
deprotected glucuronide derivatives were prepared, in order to
evaluate the influence of the carboxylic group located at the carbo-
hydrate moiety versus the oleanolic acid part with respect to bio-
logical activities. Zemplén deacetylation of 23 gave the dimethyl
ester 27 (Scheme 4). Subsequent saponification of 27 with metha-
nolic NaOH furnished the monoacid 28, whereas hydrogenolysis of
24 followed by Zemplén deacetylation gave the alternate monoacid
29, which upon further alkaline treatment afforded the free diacid
30, corresponding to the enzymatically formed monoglucuronide
of glycyrrhetinic acid.24 The 1H and 13C NMR data were in close
in agreement with the published values of glycyrrhizin recorded
for solutions in pyridine-d5.25
Entry
Donor
Acceptor
Product
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
2
2
7
3
4
3
4
3
4
3
4
3
4
3
4
11
12
5
6
10
9
80
74
65
60
60
50
97
55
60
57
75
43
55
54
7
13
13
14
14
15
15
16
16
16
16
17
18
19
20
21
22
23
24
25
26
3. Experimental
3.1. General
yields without formation of the corresponding
entries 5 and 6). The 2-deoxy-2-trichloroacetamido-D-glucopyran-
a
-isomers (Table 2,
osyl bromide donor 14 furnished the b-glycoside 19 in near quan-
titative yield (Table 2, entry 7). The b-lactosyl derivatives 21 and 22
were isolated in 60% and 57% yields, respectively (Table 2, entries 9
and 10).
Glycyrrhetinic acid ester derivatives 3, 4, 11 and 12 were pre-
pared according to published procedures.5a,10,7 Concentration of
solutions was performed at reduced pressure at temperatures
<40 °C. Dichloromethane was dried by stirring with CaH2 (5 g per
L) for 16 h, then distilled and stored under argon over molecular
sieves 0.4 nm. Silver zeolite was prepared according to literature
using powdered molecular sieves 4 Å (Merck) and was dried at
200 °C overnight prior to use.21 Column chromatography was per-
formed on Silica Gel 60 (230–400 mesh, Merck). Analytical TLC was
performed using Silica Gel 60 F254 HPTLC plates with 2.5 cm con-
centration zone (Merck). Spots were detected by treatment with
anisaldehyde–H2SO4. Ion exchange treatment was performed on
Dowex 50 WX8 resin, H+ form, 50–100 mesh. Melting points were
determined on a Kofler hot stage microscope and are uncorrected.
Optical rotations were measured with a Perkin–Elmer 243 B polar-
imeter. NMR spectra were recorded at 297 K in CD3OD and CDCl3
with a Bruker DPX 300 or Avance 400 spectrometer (1H at
300.13 MHz, 13C at 75.47 MHz or 1H at 400.13 MHz, 13C at
100.61 MHz, respectively) using standard Bruker NMR software.
1H NMR and 13C NMR spectra were referenced to internal tetra-
methylsilane (d 00). Signals assignments were based on COSY,
The broad scope of the procedure is evident from the successful
coupling of the sterically hindered 3-OH group of the triterpene
acceptor with a highly deactivated glycosyl donor such as the
methyl (2,3,4-tri-O-acetyl-glucopyranosyl bromide)uronate (16),
which furnished the monoglucuronide 23 in 75% yield.
It is worthy to note that the choice of the ester protecting
group had an influence on the reaction yields: as seen in Table
2, the methyl ester acceptor 3 consistently gave the best yields,
whereas the use of other ester protecting groups such as diphen-
ylmethyl, allyl or benzyl groups resulted in slightly reduced yields
(Table 2, entries 12–14). Since, however, the methyl ester group
at position 30 of glycyrrhetinic acid is notoriously difficult to
remove under alkaline conditions, the preparation of the fully
deblocked glycosides is better being performed by deprotection
via catalytic hydrogenation of benzyl ester type protecting group-
s.5a,10 Alternative removal of the methyl ester group of glycyrrh-
etinic acid based on enzymatic treatment has not been tested
thus far.

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Maria Carmen del Ruiz Ruiz et al. / Carbohydrate Research 344 (2009) 1063–1071
Me
Me
Me
Me
Me
Me
O
O
Me
Me
+ Glycopyranosyl-Br
RO
HO
Me
Me
Me
Me
OR'
OR'
a)
Me
Me
3
4
R' = Me
R' = CH(Ph)2
O
O
11 R' = All
12 R' = Bn
R =
OAc
OAc
OAc
OAc
O
O
AcO
AcO
AcO
OAc
OAc
17 R' = Me
13
Br
18
R' = CH(Ph)2
OAc
O
AcO
AcO
O
AcO
AcO
Cl3C(O)HN
19
20
R' = Me
R' = CH(Ph)2
Br
NHCOCCl3
14
OAc
AcO
OAc
OAc
OAc
O
OAc
OAc
O
O
O
O
AcO
O
AcO
AcO
OAc
OAc
OAc
AcO
21 R' = Me
22 R' = CH(Ph)2
Br
15
OMe
OMe
O
AcO
O
O
AcO
AcO
O
23 R' = Me
AcO
24
25
R' = CH(Ph)2
R' = All
AcO
OAc
Br
26 R' = Bn
16
Scheme 3. Reagents and conditions: Ag zeolite, CH2Cl2, molecular sieves 4 Å, rt, 4 days; yields are given in Table 2.
obtain approx. 200 counts/s. The MS had been previously tuned
OR
Me
Me
Me
O
with [Glu1]-fibrinopeptide B to give highest possible sensitivity
and a resolution of ca. 10.000 (FWHM). Mass tuning of the TOF
analyzer was done in the tandem MS mode using again
[Glu1]-fibrinopeptide B.
Me
O
O
HO
O
HO
Me
Me
OH
OR'
Me
O
3.2. Methyl 3-O-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl-(1?4)-
a)
2,3,6-tri-O-acetyl-b- -glucopyranosyl)-18-b-glycyrrhetinate (5)
D
27
28
29
23
24
R = R' = Me
b)
b)
R = H, R' = Me
R = Me, R' = H
Method 1. A suspension of acceptor 3 (100 mg, 0.212 mmol) and
powdered molecular sieves 4 Å (ꢃ100 mg) in dry CH2Cl2 (4 mL)
was stirred at rt for 15 min under Ar, then cooled to ꢀ80 °C and
a), c)
30 R = R' = H
TMSOTf (4 lL) was added dropwise. After 45 min of stirring, tri-
Scheme 4. Reagents and conditions: (a) 0.1 M NaOMe, MeOH, 3 h, rt, 93% for 27; (b)
0.2 M NaOH, MeOH, 0 °C, 3 h, 91% for 28; 91% for 30; (c) H2, 10% Pd–C, 5:2 MeOH–
EtOAc, then (a), 97% for 29.
chloroacetimidate donor 1 (332 mg, 0.425 mmol) dissolved in dry
CH2Cl2 (2 mL) was slowly added into the reaction mixture. After
1 h, the reaction was stopped by the addition of Et3N (100 lL).
HSQC and HMBC measurements. For mass spectrometry analyses,
samples were dissolved in the appropriate amount of MeCN to give
The suspension was diluted with CH2Cl2 (50 mL) and filtered
through a pad of Celite. The filtrate was washed with satd aq NaH-
CO3 and brine, dried (MgSO4) and concentrated. Chromatography
of the residue on silica gel (3:1 ? 1:1 toluene–EtOAc) afforded 5
(99.5 mg, 43%) as a white solid.
a solution of approx. 1 nmol/
the respective sample was diluted in 50% aq acetonitrile containing
mol/mL. This
lL. Just before analysis an aliquot of
0.1% formic acid to give a final concentration of ꢃ10
l
solution was subjected to offline ESI Q-TOFMS on a Waters Micro-
Rf 0.56 (1:1 n-hexane–EtOAc); 1H NMR (CDCl3, 300 MHz): d 5.66
(s, 1H, H-12), 5.18 and 5.15 (2t, 2H, H-300, H-30), 5.05 (t, 1H,
mass Q-TOF Ultima Global. Capillary voltage was adjusted to

Maria Carmen del Ruiz Ruiz et al. / Carbohydrate Research 344 (2009) 1063–1071
1067
J3 ,4 = J4 ,5 9.6 Hz, H-400), 4.94 and 4.92 (2t, 2H, H-200, H-20), 4.49 (d,
and filtered through a bed of Celite. The filtrate was washed with
1 M aq KI solution and satd aq NaHCO3 and brine, dried (MgSO4)
and concentrated in vacuo. Silica gel chromatography of the
crude mixture (2:1 ? 1:1 toluene–EtOAc) afforded 6 as off-white
powder (45 mg, 20%); Rf 0.45 (1:1 n-hexane–EtOAc); mp 188–
00 00
00 00
2H, J 8.0 Hz, H-10, H-100), 4.44 (dd, 1H, J5 ,6a 2.4, J6a ,6b 11.6 Hz, H-
0
0
00
00
60a), 4.36 (dd, 1H, J5 ,6a 4.5, J6a ,6b 12.6 Hz, H-6a00), 4.11 (dd, 1H,
00
00
00
00
J5 ,6b 6.5 Hz, H-6b0), 4.04 (dd, 1H, J5 ,6b 2.2 Hz, H-6b00), 3.73–3.55
(m, 6H, H-40, OCH3, H-50, H-500), 3.08 (dd, 1H, J3,2a 8.0, J3,2b 9.2 Hz,
H-3), 2.79 (br d, 1H, J 13.7 Hz, H-1a), 2.31 (s, 1H, H-9), 2.10–1.73
(m, 28H, 7 ꢄ Ac, H-2a, H-2b, H-15a, H-16a, H-18, H-19a, H-21a),
1.68–1.50 (m, 3H, H-6a, H-7a, H-19b), 1.35 (s, 3H, CH3-27), 1.14,
1.12 and 1.11 (3s, 9H, CH3-29, CH3-26, CH3-25), 1.48-1.13 (m, 6H,
H-6b, H-7b, H-15b, H-21b, H-22a, H-22b), 1.05–0.88 (m, 2H, H-
1b, H-16b), 0.92 (s, 3H, CH3-23), 0.80 (s, 3H, CH3-28),0.75 (s, 3H,
CH3-24), 0.69 (br d, 1H, H-5); 13C NMR (CDCl3) d: 200.05 (C-11),
175.81 (C-30), 170.43, 170.24, 170.10, 169.81, 169.23, 169.16,
169.02 (C-13, COOCH3), 128.33 (C-12), 102.67 (C-10), 100.71 (C-
100), 90.39 (C-3), 77.90 (C-40), 72.90, 72.58, 72.41 and 71.92, (C-500,
C-50, C-30, C-300), 71.90 and 71.59 (C-20, C-200), 67.79 (C-400), 62.14
(C-60), 61.58 (C-600), 60.36 (C-9), 55.21 (C-5), 51.77 (OCH3), 48.37
(C-18), 45.35 (C-8), 44.01 (C-20), 43.14 (C-14), 41.07 (C-19),
39.16 (C-4), 39.00 (C-1), 37.70 (C-22), 36.77 (C-10), 32.69 (C-7),
31.81 (C-17), 31.10 (C-21), 28.49 (C-29), 28.31 (C-28), 27.65 (C-
23), 26.44 (C-16), 26.37 (C-15), 25.66 (C-2), 23.32 (C-27), 21.03,
20.81, 20.69, 20.62, 20.51 (CH3CO), 18.54 (C-26), 17.24 (C-6),
16.24 (C-24), and 16.20 (C-25).
0
0
00
00
192 °C, ½a 2D0
ꢅ
+23 (c 0.5, CHCl3); NMR data were identical to
published data.5
3.4. 3,4,6-Tri-O-acetyl-{(S)-1,2-O-[1-(30-O-diphenylmethyloxy-
carbonyl-11-oxo-30-norolean-12-ene-3-yloxy)ethylidene]}-
-glucopyranose (8) and diphenylmethyl 3-O-(2,3,4,6-tetra-O-
acetyl-b- -glucopyranosyl)-18-b-glycyrrhetinate (9)
a-
D
D
To a suspension of 7 (50 mg, 0.121 mmol) in dry CH2Cl2 (3 mL)
containing 4 (78 mg, 0.121 mmol) and powdered 4 Å molecular
sieves (200 mg) were added Ag2CO3 (167 mg, 0.605 mmol) and I2
(31 mg, 0.121 mmol). The suspension was stirred at rt for 4 days
protected from light, then diluted with CH2Cl2 (50 mL) and filtered
through CeliteÒ. The filtrate was washed with satd aq NaHCO3 and
brine, dried (MgSO4) and concentrated. The residue was purified by
flash chromatography (2:1 n-hexane–EtOAc) to afford 8 (60 mg,
51%) as colourless syrup. Rf 0.71 (1:1 n-hexane–EtOAc); ½a D20
ꢅ
+91
(c 1.0, CHCl3); selected 1H NMR data (CDCl3, 400 MHz): d 7.38–
0
0
Method 2. Acceptor 3 (46 mg, 0.095 mmol), donor 1 (150 mg,
0.192 mmol) and powdered molecular sieves 4 Å (ꢃ150 mg) were
dissolved in dry CH2Cl2 (5 mL) under Ar. The reaction mixture
was stirred at ꢀ40 °C for 30 min and a solution of (C6F5)3B
(7.3 mg, 0.014 mmol) in dry CH2Cl2 (1 mL) was added dropwise
into the solution. After 1 h at ꢀ40 °C the reaction was allowed to
reach 20 °C and the reaction mixture was left overnight at rt. Then,
7.27 (m, 10H, H-Ar), 6.93 (s, 1H, CHPh2), 5.69 (d, 1H, J1 ,2 ꢃ 4.0 Hz,
H-10), 5.51 (s, 1H, H-12), 5.19 (t, 1H, H-30), 4.90 (dd, 1H, H-40), 4.19
(d, 1H, J4 ,5 4.4 Hz, H-50), 3.95 (m, 1H, H-60), 3.23 (m, 1H, H-3), 2.79
(br d, 1H, J 13.6 Hz, H-1), 2.31 (s, 1H, H-9), 2.11, 2.09, 2.08 (3s, 9H,
3 ꢄ Ac), and 1.74 (s, 3H, CH3-endo).
0
0
Further elution of the column with 1:1 n-hexane–EtOAc fur-
nished the saponin 9 (35 mg, 29%) as a white solid. Rf 0.42 (3:2
the reaction was quenched by the addition of Et3N (100
lL), and
n-hexane–EtOAc); ½a D20
ꢅ
+84 (c 0.36, CHCl3); 1H NMR (CDCl3,
was processed as described above to furnish 5 (42 mg, 40%) as a
white solid.
300 MHz): d 7.38–7.16 (m, 10H, H-Ar), 6.93 (s, 1H, CHPh2), 5.51
(s, 1H, H-12), 5.21 (t, 1H, J3 ,4 = J3 ,2 9.6, H-30), 5.06–5.00 (m, 2H,
0
0
0
0
H-40, H-20), 4.54 (d, 1H, J1 ,2 8.0 Hz, H-10), 4.24 (dd, 1H, J5 ,6a 5.8,
0
0
0
0
Method 3. A suspension of acceptor 3 (100 mg, 0.212 mmol) and
powdered molecular sieves 4 Å (ꢃ100 mg) in dry CH2Cl2 (4 mL)
was stirred at rt for 15 min under Ar, then cooled to ꢀ60 °C and
J6a ,6b 12.2 Hz, H-6a0), 4.10 (dd, 1H, J6 ,5 2.5 Hz, H-6b0), 3.69 (ddd,
1H, H-50), 3.12 (dd, 1H, J ꢃ 8.2 Hz, H-3), 2.80 (ddd, 1H, J 10.4 Hz,
H-1a), 2.29 (s, 1H, H-9), 2.12–1.73 (m, 28H, 7 ꢄ Ac, H-2a, H-2b,
H-15a, H-16a, H-18, H-19a, H-21a), 1.70–1.53 (m, 3H, H-6a, H-
7a, H-19b), 1.34 (s, 3H, CH3-27), 1.17, 1.12 and 1.08 (3s, 9H, CH3-
29, CH3-25, CH3-26), 1.46–1.13 (m, 6H, H-6b, H-7b, H-15b,
H-21b, H-22a, H-22b), 1.03–0.85 (m, 2H, H-1b, H-16b), 0.93 (s,
3H, CH3-23), 0.80 (s, 3H, CH3-28), 0.77 (s, 3H, CH3-24), and
0.69 (br d, 1H, H-5); 13C NMR (CDCl3) d: 199.94 (C-11), 175.14
(C-30), 170.44, 170.24, 170.37, 170.21, 169.25, 168.87 (COCH3,
C-13), 140.04 (C-arom.), 128.60, 128.42, 128.12, 127.80, 127.32,
126.93 (C-arom., C-12), 102.89 (C-10), 90.51 (C-3), 76.63 (CHPh2),
72.87 (C-30), 71.76 (C-40), 71.52 (C-50), 68.79 (C-20), 62.31 (C-60),
61.73 (C-9), 55.27 (C-5), 48.04 (C-18), 45.32 (C-8), 44.00 (C-20),
43.12 (C-14), 41.07 (C-19), 39.23 (C-4), 39.08 (C-1), 37.52 (C-22),
36.79 (C-10), 32.74 (C-7), 31.72 (C-17), 31.09 (C-21), 28.29
(C-29), 28.20 (C-28), 27.66 (C-23), 26.43 (C-16), 26.30 (C-15),
25.72 (C-2), 23.32 (C-27), 20.67, 20.68, 20.69, 20.59 (CH3CO),
18.66 (C-26), 18.42, 17.32 (C-6), 16.38 (C-24) and 16.26 (C-25).
0
0
0
0
BF3ꢂEt2O (13
lL) was added dropwise. After stirring for 45 min, tri-
chloroacetimidate donor 1 (332 mg, 0.425 mmol) dissolved in dry
CH2Cl2 (2 mL) was slowly added into the reaction mixture. After
2 h, the reaction was stopped by the addition of Et3N (100 lL).
Work-up as described above afforded 5 (42 mg, 18%) as a white
solid.
Method 4. Trichloroacetimidate donor 1 (50 mg; 0.064 mmol),
acceptor 3 (26.5 mg, 0.056 mmol) and powdered molecular sieves
4 Å (100 mg) were dissolved in dry CH2Cl2 (5 mL) under Ar. The
mixture was stirred at ꢀ30 °C for 4 h. Then anhydrous ZnBr2
(8.5 mg; 0.038 mmol) was added in one portion into the suspen-
sion. The reaction was maintained at rt for 2 h and was monitored
by TLC using 3:1 CHCl3–EtOAc and 1:1 toluene–EtOAc. Stirring of
the reaction was then continued under reflux for 15 h. Acetic
anhydride (0.1 mL, 1.06 mmol) was added at rt and the reaction
mixture was stirred for 3 h. Work-up as described above gave 5
(9 mg; 13%).
3.3. Diphenylmethyl 3-O-(2,3,4,6-tetra-O-acetyl-b-
D-glucopyr-
3.5. General method for silver zeolite promoted glycosylation
anosyl-(1?4)-2,3,6-tri-O-acetyl-b-
D-glucopyranosyl)-18-b-
glycyrrhetinate (6)
Acetobromocellobiose 2 (100 mg, 0.143 mmol), acceptor 3
(34 mg, 0.0715 mmol), silver zeolite (ꢃ250 mg) and powdered
4 Å molecular sieves (ꢃ100 mg) were suspended in dry CH2Cl2
(3 mL) and stirred at rt while shielded from light for 4 days. The
suspension was diluted with CH2Cl2 (50 mL), stirred under sonica-
tion for 5 min and filtered through a pad of CeliteÒ. The filtrate was
washed with 1 M Na2S2O3 solution, satd aq NaHCO3, dried (MgSO4)
and concentrated in vacuo. The residue was purified by silica gel
chromatography (3:2 ? 1:1 n-hexane–EtOAc) to afford 63 mg of
5 (80%) as a white solid.
A suspension of 4 (112 mg, 0.18 mmol) in dry CH2Cl2 (8 mL)
containing powdered molecular sieves 4 Å (ꢃ150 mg) and a mix-
ture of Hg(CN)2 (68 mg, 0.27 mmol) and HgBr2 (130 mg,
0.36 mmol) was cooled to 0 °C. Hepta-O-acetyl-cellobiosyl bromide
2 (250 mg, 0.360 mmol) dissolved in 2 mL of dry CH2Cl2 was added
dropwise with stirring. After stirring for 2 h at 0 °C the reaction
was allowed to reach 20 °C and the suspension was stirred over-
night at rt. The reaction mixture was diluted with CH2Cl2 (50 mL)

1068
Maria Carmen del Ruiz Ruiz et al. / Carbohydrate Research 344 (2009) 1063–1071
Similarly, glycosidation of 2 (100 mg, 0.145 mmol) with 4
32.21 (C-17), 31.49 (C-21), 28.89 (C-29), 28.73 (C-28), 28.09(C-23),
26.84 (C-16), 26.76 (C-15), 26.23 (C-2), 23.72 (C-27), 21.27, 21.14,
21.09, 21.04 (CH3CO), 19.04 (C-26), 17.75 (C-6), 16.76 (C-24),
16.70 (C-25). ESI-TOFMS: m/z = 815.5206 [M+H]+; calcd 815.4581.
(46 mg, 0.071 mmol) was accomplished as described for the prep-
aration of 5. The product was purified by column chromatography
(3:2 ? 1:1 n-hexane–EtOAc) to yield 6 as a colourless syrup
(65 mg, 74%).
In addition, coupling of acetobromoglucose
7
(100 mg,
3.5.3. Diphenylmethyl 3-O-(2,3,4,6-tetra-O-acetyl-b-D-galactopyr-
0.243 mmol), acceptor (75 mg, 0.121 mmol), silver zeolite
4
anosyl)-18-b-glycyrrhetinate (18)
(ꢃ250 mg) and powdered 4 Å molecular sieves (ꢃ200 mg) and
Acetobromogalactose 13 (100 mg, 0.243 mmol), acceptor 4
(98 mg, 0.121 mmol), silver zeolite (ꢃ150 mg) and powdered 4 Å
molecular sieves (ꢃ100 mg) were suspended in dry CH2Cl2
(3 mL) and treated as described for 5 to afford 58 mg (50%) of 18
work-up as described afforded 69 mg of 9 (60%) as a white solid.
3.5.1. Methyl 3-O-(2,3,4,6-tetra-O-acetyl-b-D-glucopyranosyl)-18-
b-glycyrrhetinate (10)
as a colourless syrup; Rf 0.64 (1:1 n-hexane–EtOAc); ½a D20
ꢅ
+74 (c
The compound was prepared according to the general proce-
dure from bromide 7 (250 mg, 0.610 mmol), acceptor 3 (98 mg,
0.203 mmol), silver zeolite (ꢃ250 mg) and powdered 4 Å molecu-
lar sieves (ꢃ200 mg). Chromatography of the processed reaction
mixture on silica gel (3:2 ? 1:1 n-hexane–EtOAc) afforded
114 mg of 10 (65%) as a white solid; Rf 0.42 (3:2 n-hexane–EtOAc);
0.5, CHCl3); 1H NMR (CDCl3, 300 MHz): d 7.39–7.27 (m, 10H, H-
0
0
Ar), 6.90 (s, 1H, CHPh2), 5.52 (s, 1H, H-12), 5.36 (dd, 1H, J3 ,4 3.5,
J4 ,5 0.9 Hz, H-40), 5.26 (dd, 1H, J1 ,2 7.9, J2 ,3 10.5 Hz, H-20), 5.02
0
0
0
0
0
0
(dd, 1H, H-30), 4.51 (d, 1H, H-10), 4.195 (dd, 1H, J5 ,6a 7.1, J6a ,6b
0
0
0
0
11.2 Hz, H-60a), 4.10 (dd, 1H, J5 ,6 b 6.4 Hz, H-60b), 3.90 (ddd, 1H, H-
50), 3.12 (dd, 1H, J 5.8, J 10.5 Hz, H-3), 2.80 (ddd, 1H, J 13.5 Hz,
H-1a), 2.30 (s, 1H, H-9), 2.17–1.72 (m, 19H, 4 ꢄ Ac, H-2a, H-2b,
H-15a, H-16a, H-18, H-19a, H-21a), 1.71–1.50 (m, 3H, H-6a, H-
7a, H-19b), 1.45–1.15 (m, 6H, H-6b, H-7b, H-15b, H-21b, H-22a,
H-22b), 1.365 (s, 3H, CH3-27), 1.17, 1.13 and 1.08 (3s, 9H, CH3-
29, CH3-25, CH3-26), 0.93 (s, 3H, CH3-23), 1.05–0.88 (m, 2H, H-
16b, H-1b), 0.78 (s, 3H, CH3-24), 0.66 (s, 3H, CH3-28) and 0.70 (br
d, 1H, H-5); 13C NMR (CDCl3): d 199.91 (C-11), 175.15 (C-30),
170.44, 170.37, 170.21, 169.25, 168.87 (C-13, COCH3), 140.04 (C-
arom.), 128.60, 128.42, 128.12, 127.80, 127.23, 126.93 (C-12, C-
arom.), 103.47 (C-10), 90.53 (C-3), 70.94 (C-50), 70.35 (C-30), 69.20
(C-20), 67.05 (C-40), 61.65 (C-60), 61.42 (C-9), 55.20 (C-5), 47.97
(C-18), 45.26 (C-8), 43.94 (C-20), 43.06 (C-14), 41.05 (C-19),
39.18 (C-4), 39.03 (C-1), 37.41 (C-22), 36.73 (C-10), 32.66 (C-7),
31.68 (C-17), 31.09 (C-21), 28.25 (C-29), 28.20 (C-28), 27.66 (C-
23), 26.38 (C-16), 26.30 (C-15), 25.79 (C-2), 23.24 (C-27), 20.83,
20.69, 20.59 (CH3CO), 18.59 (C-26), 17.32 (C-6), 16.34 (C-24) and
16.26 (C-25). ESI-TOFMS: m/z = 967.560 [M+H]+ calcd 967.5207.
0
0
½
a 2D0 +84 (c 0.36, CHCl3); 1H NMR (CDCl3, 300 MHz): d 5.66 (s, 1H,
ꢅ
H-12), 5.24 (t, 1H, J3 ,4 9.6 Hz, H-30), 5.06–5.01 (m, 2H, H-40, H-
0
0
20), 4.54 (d, 1H, J1 ,2 8.0 Hz, H-10), 4.24 (dd, 1H, J5 ,6a 5.8, J6a ,6b
0
0
0
0
0
0
12.2 Hz, H-6a0), 4.11 (dd, 1H, H-6b0), 3.71–3.67 (m, 4H, OCH3, H-
50), 3.11 (t, 1H, J ꢆ 8.2 Hz, H-3), 2.80 (br d, 1H, J 10.4 Hz, H-1a),
2.31 (s, 1H, H-9), 2.11–1.75 (m, 19H, 4 ꢄ Ac, H-2a, H-2b, H-15a,
H-16a, H-18, H-19a, H-21a), 1.70–1.53 (m, 3H, H-6a, H-7a, H-
19b), 1.35 (s, 3H, CH3-27), 1.14, 1.13 and 1.12 (3s, 9H, CH3-29,
CH3-25, CH3-26), 1.48–1.13 (m, 6H, H-6b, H-7b, H-15b, H-21b, H-
22a, H-22b), 1.03–0.85 (m, 2H, H-1b, H-16b), 0.93 (s, 3H, CH3-
23), 0.80 and 0.77 (2s, 6H, CH3-28, CH3-24), and 0.69 (br d, 1H,
H-5); 13C NMR (CDCl3): d 200.04 (C-11), 176.86 (C-30), 170.64,
170.24, 170.36, 169.37, 169.14, 169.08 (C-13, COCH3), 128.51
(C-12), 102.86 (C-10), 90.50 (C-3), 72.84 (C-40), 71.65 (C-50), 71.49
(C-30), 68.78 (C-20), 62.28 (C-60), 61.74 (C-9), 55.24 (C-5), 51.76
(OCH3), 48.36 (C-18), 45.34 (C-8), 44.00 (C-20), 43.12 (C-14),
41.06 (C-19), 39.17 (C-4), 39.01 (C-1), 37.69 (C-22), 36.78 (C-10),
32.69 (C-7), 31.79 (C-17), 31.09 (C-21), 28.47 (C-29), 28.31 (C-
28), 27.67 (C-23), 26.44 (C-16), 26.37 (C-15), 25.68 (C-2), 23.31
(C-27), 20.73, 20.68, 20.61 and 20.58 (CH3CO), 18.64 (C-26),
17.34 (C-6), 16.32 (C-24) and 16.27 (C-25). ESI-TOFMS:
m/z = 815.5206 [M+H]+; calcd 815.4581.
3.5.4. Methyl 3-O-(3,4,6-tri-O-acetyl-2-deoxy-2-trichloroaceta-
mido-b-
D
-glucopyranosyl)-18-b-glycyrrhetinate (19)
-glucopyr-
3,4,6-Tri-O-acetyl-2-deoxy-2-trichloroacetamido-
D
anosyl bromide 14 (260 mg, 0.506 mmol), acceptor 3 (82 mg,
0.170 mmol), silver zeolite (ꢃ 250 mg) and powdered 4 Å molecu-
lar sieves (ꢃ150 mg) were suspended in dry CH2Cl2 (5 mL) and
treated as described for 5 to give 150 mg (97%) of 19 as a colourless
3.5.2. Methyl 3-O-(2,3,4,6-tetra-O-acetyl-b-
18-b-glycyrrhetinate (17)
D-galactopyranosyl)-
Acetobromogalactose 13 (250 mg, 0.610 mmol), acceptor 3
(98 mg, 0.203 mmol), silver zeolite (ꢃ250 mg) and powdered 4 Å
molecular sieves (ꢃ200 mg) were suspended in dry CH2Cl2
(5 mL) and treated as described for 5 to afford 105 mg (60%) of
solid; Rf 0.37 (3:2 n-hexane–EtOAc); ½a D20
ꢅ
+73.2 (c 0.5, CHCl3); 1H
NMR (CDCl3, 300 MHz): d 6.79 (d, 1H, J 8.7 Hz, NH), 5.66 (s, 1H,
H-12), 5.34 (dd, 1H, J2 ,3 10.6 Hz, H-30), 5.06 (t, 1H, J3 ,4 9.4 Hz, H-
0
0
0
0
40), 4.73 (d, 1H, J1 ,2 8.2 Hz, H-10), 4.27 (dd, 1H, J5 ,6a 5.9, J6a ,6b
0
0
0
0
0
0
17 as a white solid; Rf 0.51 (3:2 n-hexane–EtOAc); ½a D20
ꢅ
+91.4 (c
12.4 Hz H-6a0), 4.12 (dd, 1H, J5 ,6ab 2.7 Hz, H-6b0), 3.97 (ddd, 1H,
H-20), 3.73 (ddd, 1H, H-50), 3.69 (s, 3H, OCH3), 3.12 (t, 1H, J
8.3 Hz, H-3), 2.80 (ddd, 1H, J 13.6 Hz, H-1a), 2.30 (s, 1H, H-9),
2.17–1.72 (m, 19H, 4 ꢄ Ac, H-2a, H-2b, H-15a, H-16a, H-18, H-
19a, H-21a), 1.71–1.50 (m, 3H, H-6a, H-7a, H-19b), 1.45–1.15 (m,
6H, H-6b, H-7b, H-15b, H-21b, H-22a, H-22b), 1.35 (s, 3H, CH3-
27), 1.14, 1.13 and 1.08 (3s, 9H, CH3-29, CH3-25, CH3-26), 0.92 (s,
3H, CH3-23), 1.05–0.85 (m, 2H, H-16b, H-1b), 0.80 (2s, 6H, CH3-
24, CH3-28) and 0.78 (br d, 1H, H-5); 13C NMR (CDCl3): d 200.04
(C-11), 176.91 (C-30), 170.85, 170.64, 169.34, 169.58 (COCH3, C-
13), 161.58 (COCCl3), 128.55 (C-12), 102.32 (C-10), 90.51 (COCCl3),
90.52 (C-3), 71.74 (C-50), 71.49 (C-30), 68.73 (C-40), 62.34 (C-60),
61.79 (C-9), 57.76 (C-20), 55.34 (C-5), 51.79 (OCH3), 48.41 (C-18),
45.38 (C-8), 44.05 (C-20), 43.17 (C-14), 41.13 (C-19), 39.29 (C-4),
39.11 (C-1), 37.74 (C-22), 36.81 (C-10), 32.73 (C-7), 31.84 (C-17),
31.14 (C-21), 28.51 (C-29), 28.36 (d.i., C-28, C-23), 26.49 and
26.42 (C-16, C-15), 25.69 (C-2), 23.36 (C-27), 20.77, 20.61, 20.56
(CH3CO), 18.69 (C-26), 17.37 (C-6), and 16.32 (d.i., C-24, C-25).
ESI-TOFMS: m/z = 916.386 [M+H]+; calcd 916.349.
0
0
0.33, CHCl3); 1H NMR (CDCl3, 400 MHz): d 5.67 (s, 1H, H-12),
5.36 (dd, 1H, J3 ,4 3.4, J5 ,4 1.2 Hz, H-40), 5.26 (dd, 1H, J2 ,3 10.6 Hz,
0
0
0
0
0
0
H-20), 5.02 (dd, 1H, H-30), 4.50 (d, 1H, J1 ,2 8.0 Hz, H-10), 4.195
0
0
(dd, 1H, J5 ,6a 6.8, J6a ,6b 11.2 Hz, H-60a), 4.095 (dd, 1H, J5 ,6 b
6.8 Hz, H-60b), 3.89 (ddd, 1H, H-50), 3.69 (s, 3H, OCH3), 3.11 (dd,
1H, J 5.8, J 10.8 Hz, H-3), 2.80 (ddd, 1H, J 13.6 Hz, H-1a), 2.30 (s,
1H, H-9), 2.16–1.77 (m, 19H, 4 ꢄ Ac, H-2a, H-2b, H-15a, H-16a,
H-18, H-19a, H-21a), 1.68–1.53 (m, 3H, H-6a, H-7a, H-19b), 1.48–
1.15 (m, 6H, H-6b, H-7b, H-15b, H-21b, H-22a, H-22b), 1.355 (s,
3H, CH3-27), 1.15, 1.13 and 1.12 (3s, 9H, CH3-29, CH3-25,
CH3-26), 0.93 (s, 3H, CH3-23), 1.05–0.88 (m, 2H, H-16b, H-1b),
0.80 and 0.79 (2s, 6H, CH3-24, CH3-28), 0.70 (br d, 1H, H-5); 13C
NMR (CDCl3) d: 200.11 (C-11), 176.91 (C-30), 170.46, 170.41,
170.25, 169.29, 169.16 (C-13, COCH3), 128.57 (C-12), 103.55 (C-
10), 90.64 (C-3), 71.38 (C-50), 70.79 (C-30), 69.62 (C-20), 67.48
(C-40), 62.13 (C-60), 61.82 (C-9), 55.65 (C-5), 52.21 (OCH3), 48.77
(C-18), 45.34 (C-8), 44.42 (C-20), 43.53 (C-14), 41.45 (C-19),
39.61 (C-4), 39.41 (C-1), 38.09 (C-22), 37.17 (C-10), 33.09 (C-7),
0
0
0
0
0
0

Maria Carmen del Ruiz Ruiz et al. / Carbohydrate Research 344 (2009) 1063–1071
1069
3.5.5. Diphenylmethyl 3-O-(3,4,6-tri-O-acetyl-2-deoxy-2-trichlo-
roacetamido-b- -glucopyranosyl)-18-b-glycyrrhetinate (20)
3,4,6-Tri-O-acetyl-2-deoxy-2-trichloroacetamido- -glucopyr-
3.5.8. Methyl 3-O-(methyl 2,3,4-tri-O-acetyl-b-
luronate)-18-b-glycyrrhetinate (23)
Methyl 2,3,4-tri-O-acetyl- -glucopyranosyluronate bromide 16
D
-glucopyranosy-
D
D
D
anosyl bromide 14 (250 mg, 0.49 mmol), acceptor 4 (124 mg,
0.195 mmol), silver zeolite (ꢃ300 mg) and powdered 4 Å molecu-
lar sieves (ꢃ200 mg) were suspended in dry CH2Cl2 (5 mL) and
treated as described for 5 to afford 115 mg (55%) of 20 as a white
(500 mg, 1.21 mmol), acceptor 3 (190 mg, 0.392 mmol), silver zeo-
lite (ꢃ750 mg) and powdered 4 Å molecular sieves (ꢃ400 mg)
were suspended in dry CH2Cl2 (10 mL) and were processed as de-
scribed for 5 to afford 232 mg (75%) of 23 as a colourless syrup;
solid; Rf 0.43 (3:2 n-hexane–EtOAc); ½a D20
ꢅ
ꢀ16.7 (c 0.3, CHCl3); 1H
Rf 0.46 (3:2 n-hexane–EtOAc); ½a D20
ꢅ
+55.5 (c 0.3, CHCl3); 1H NMR
NMR (CDCl3, 400 MHz): d 7.40–7.25 (m, 10H, H-Ar), 6.93 (s, 1H,
(CDCl3, 400 MHz): d 5.66 (s, 1H, H-12), 5.27–5.18 (m, 2H, H-30,
CHPh2), 6.84 (d, 1H, J2 ,NH 8.8 Hz, NH), 5.51 (s, 1H, H-12), 5.35
H-40), 5.05 (dd, 1H, J1 ,2 7.9, J2 ,3 9.3 Hz, H-20), 4.59 (d, 1H, H-10),
0
0
0
0
0
(dd, 1H, J2 ,3 11.2, J3 ,4 9.2 Hz, H-30), 5.06 (t, 1H, H-40), 4.74 (d,
4.00 (d, 1H, J4 ,5 9.4 Hz, H-50), 3.76 (s, 3H, 60-OCH3), 3.68 (s, 3H,
30-OCH3), 3.12 (dd, 1H, J 6.6, J 9.7 Hz, H-3), 2.78 (ddd, 1H, J
13.5 Hz, H-1a), 2.31 (s, 1H, H-9), 2.10–1.78 (m, 16H, 3 ꢄ Ac, H-2a,
H-2b, H-15a, H-16a, H-18, H-19a, H-21a), 1.69–1.50 (m, 3H, H-
6a, H-7a, H-19b), 1.46–1.13 (m, 6H, H-6b, H-7b, H-15b, H-21b,
H-22a, H-22b), 1.39 (s, 3H, CH3-27), 1.19, 1.15 and 1.13 (3s, 9H,
CH3-29, CH3-25, CH3-26), 0.925 (s, 3H, CH3-23), 1.05–0.88 (m, 2H,
H-16b, H-1b), 0.80 (s, 3H, CH3-28), 0.76 (s, 3H, CH3-24) and 0.68
(br d, 1H, H-5); 13C NMR (CDCl3): d 200.04 (C-11), 176.92 (C-30),
171.16 (C-60), 170.64, 170.30, 169.34, 169.12, 169.03, 167.20
(COCH3, C-13), 128.56 (C-12), 102.84 (C-10), 90.52 (C-3), 72.48 (C-
50), 72.21 (C-30), 71.52 (C-20), 69.52 (C-40), 61.78 (C-9), 55.23 (C-
5), 51.89 (60-OCH3), 51.80 (30-OCH3), 48.38 (C-18), 45.38 (C-14),
44.05 (C-20), 43.15 (C-8), 41.11 (C-19), 39.3 (C-4), 39.015 (C-1),
37.74 (C-22), 36.79 (C-10), 32.73 (C-7), 31.83 (C-17), 31.14 (C-
21), 28.51 (C-29), 28.35 (C-28), 27.73 (C-23), 26.48 and 26.42 (C-
15, C-16), 25.63 (C-2), 23.37 (C-27), 20.68, 20.66, 20.53 (CH3CO),
18.68 (C-26), 17.37 (C-6), 16.36 and 16.32 (C-24, C-25). ESI-TOFMS:
m/z = 801.4869 [M+H]+; calcd 801.4425.
0
0
0
0
0
0
1H, J1 ,2 8.0 Hz, H-10), 4.27 (dd, 1H, J5 ,6a 6.0, J6a ,6b 12.0 Hz H-
0
0
0
0
0
0
6a0), 4.12 (dd, 1H, J5 ,6ab 2.8 Hz, H-6b0), 3.98 (ddd, 1H, H-20),
3.73 (ddd, 1H, H-50), 3.13 (dd, 1H, J 9.2, J 7.2 Hz, H-3), 2.80
(ddd, 1H, J 13.6 Hz, H-1a), 2.28 (s, 1H, H-9), 2.14–1.73 (m, 19H,
4 ꢄ Ac, H-2a, H-2b, H-15a, H-16a, H-18, H-19a, H-21a), 1.69–
1.50 (m, 3H, H-6a, H-7a, H-19b), 1.46–1.13 (m, 6H, H-6b, H-7b,
H-15b, H-21b, H-22a, H-22b), 1.34 (s, 3H, CH3-27), 1.17, 1.12
and 1.08 (3s, 9H, CH3-29, CH3-25, CH3-26), 0.92 (s, 3H, CH3-23),
1.00–0.88 (m, 2H, H-16b, H-1b), 0.79 (s, 3H, CH3-24), 0.66 (s,
3H, CH3-28) and 0.67 (br d, 1H, H-5); 13C NMR (CDCl3): d
199.92 (C-11), 175.21 (C-30), 170.90, 170.67, 169.36, 168.91
(COCH3, C-13), 161.61 (COCCl3), 140.10 (C-arom.), 128.64,
128.51, 128.47, 128.16, 127.86, 127.29, 127.28 (C-arom., C-12),
102.28 (C-10), 92.26 (COCCl3), 90.47 (C-3), 71.72 and 71.48 (C-30,
C-50), 68.73 (C-40), 62.36 (C-60), 61.73 (C-9), 56.72 (C-20), 55.29
(C-5), 48.02 (C-18), 45.31 (C-8), 44.00 (C-20), 43.13 (C-14),
41.14 (C-19), 39.28 (C-4), 39.12 (C-1), 37.48 (C-22), 36.79 (C-
10), 33.71 (C-7), 31.73 (C-17), 31.16 (C-21), 28.35 (C-29), 28.29
(C-28), 28.26 (C-23), 26.44 (C-16), 26.37 (C-15), 25.67 (C-2),
23.32 (C-27), 20.81, 20.63, 20.58 (CH3CO), 18.66 (C-26), 17.35
(C-6), 16.32 (C-24), 16.31 (C-25). ESI-TOFMS: m/z = 1068.5415
[M+H]+; calcd 1068.4198.
0
0
3.5.9. Diphenylmethyl 3-O-[methyl (2,3,4-tri-O-acetyl-b-
glucopyranosyluronate)]-18-b-glycyrrhetinate (24)
D-
Methyl 2,3,4-tri-O-acetyl-D-glucopyranosyluronate bromide 16
(500 mg, 1.21 mmol), acceptor 4 (310 mg, 0.486 mmol), silver zeo-
lite (ꢃ750 mg) and powdered 4 Å molecular sieves (ꢃ400 mg)
were suspended in dry CH2Cl2 (10 mL) and were processed as de-
scribed for 5 to give 208 mg (45%) of 24 as a colourless syrup; Rf
3.5.6. Methyl 3-O-[2,3,4,6-tetra-O-acetyl-b-
D
-galactopyranosyl-
(1?4)-2,3,6-tri-O-acetyl-b-
D-glucopyranosyl]-18-b-
glycyrrhetinate (21)
Acetobromolactose 15 (100 mg; 0.243 mmol), acceptor
3
0.54 (1:1 n-hexane–EtOAc); ½a D20
ꢅ
ꢀ8.3 (c 0.3, CHCl3); 1H NMR
(98 mg, 0.121 mmol), silver zeolite (ꢃ150 mg) and powdered
4 Å molecular sieves (ꢃ100 mg) were suspended in dry CH2Cl2
(3 mL) and treated as described for 5 to give 58 mg (60%) of
21 as a colourless solid; mp 135–139 (dec.); Rf 0.64 (1:1 n-hex-
(CDCl3, 300 MHz): d 7.40–7.23 (m, 10H, H-Ar), 6.93 (s, 1H, CHPh2),
5.51 (s, 1H, H-12), 5.29–5.18 (m, 2H, H-30, H-40), 5.06 (t, 1H, J2 ,3
0
0
8.6 Hz, H-20), 4.59 (d, 1H, J1 ,2 7.8 Hz, H-10), 4.01 (d, 1H, J4 ,5
0
0
0
0
9.3 Hz, H-50), 3.76 (s, 3H, 60-OCH3), 3.15–3.10 (m, 1H, H-3), 2.81–
2.77 (br d, 1H, J 13.4 Hz, H-1), 2.29 (s, 1H, H-9), 2.10–1.78 (m,
16H, 3 ꢄ Ac, H-2a, H-2b, H-15a, H-16a, H-18, H-19a, H-21a),
1.69–1.50 (m, 3H, H-6a, H-7a, H-19b), 1.46–1.13 (m, 6H, H-6b,
H-7b, H-15b, H-21b, H-22a, H-22b), 1.34 (s, 3H, CH3-27), 1.17,
1.16 and 1.08 (3s, 9H, CH3-29, CH3-25, CH3-26), 0.92 (s, 3H, CH3-
23), 1.05–0.88 (m, 2H, H-16b, H-1b), 0.76 (s, 3H, CH3-28), 0.66 (s,
3H, CH3-24) and 0.68 (br d, 1H, H-5).13C NMR (CDCl3): d 199.86
(C-11), 175.18 (C-30), 171.13 (C-60), 170.28, 169.65, 169.62,
167.18, 166.65 (COCH3, C-13), 140.07 (C-arom.), 128.64, 128.53,
128.46, 128.15, 127.84, 127.26 (C-arom., C-12), 102.82 (C-10),
90.46 (C-3), 76.64 (CHPh2), 72.45 (C-30), 72.21 (C-50), 71.51 (C-20),
69.48 (C-40), 61.72 (C-9), 55.19 (C-5), 52.86 (60-OMe), 48.02 (C-
18), 45.29 (C-14), 43.99 (C-20), 43.10 (C-8), 41.11 (C-19), 39.21
(C-4), 39.08 (C-1), 37.74 (C-22), 36.76 (C-10), 32.73 (C-7), 31.73
(C-17), 31.14 (C-21), 28.28 (C-29), 28.24 (C-28), 27.71 (C-23),
26.44 (C-16), 26.37 (C-15), 25.63 (C-2), 23.31 (C-27), 20.81,
20.66, 20.59 (CH3CO), 18.65 (C-26), 17.36 (C-6), 16.35 (C-24),
16.31 (C-25). ESI-TOFMS: m/z = 953.4869 [M+H]+; calcd 953.5051.
ane–EtOAc); ½a 2D0
ꢅ
+120 (c 1.0, CHCl3); 1H NMR data were compa-
rable to reported values.9 13C NMR (CDCl3): d 200.03 (C-11),
176.84 (C-30), 170.30, 170.07, 169.97, 169.81, 169.35, 169.12,
169.08 (C-13, COCH3), 128.51 (C-12), 102.66 (C-10), 101.06
(C-100), 90.44 (C-3), 76.57 (C-40), 72.91 (C-30), 72.34 (C-500), 72.04
(C-20), 70.95 (C-300), 70.67 (C-50), 69.11 (C-200), 66.63 (C-400),
62.26 (C-600), 61.73 (C-9), 60.83 (C-60), 55.23 (C-5), 51.73 (OCH3),
48.37 (C-18), 45.34 (C-8), 44.00 (C-20), 43.13 (C-14), 41.08
(C-19), 39.15 (C-4), 39.01 (C-1), 37.69 (C-22), 36.78 (C-10),
32.70 (C-7), 31.79 (C-17), 31.09 (C-21), 28.47 (C-29), 28.29
(C-28), 27.65 (C-23), 26.44 (C-16), 26.38 (C-15), 25.65 (C-2),
23.30 (C-27), 20.77, 20.68, 20.58, 20.45 (CH3CO), 18.64 (C-26),
17.34 (C-6), 16.31 (C-24), 16.25 (C-25).
3.5.7. Diphenylmethyl 3-O-[2,3,4,6-tetra-O-acetyl-b-
D-galacto-
pyranosyl-(1?4)-2,3,6-tri-O-acetyl-b-D-glucopyranosyl]-18-b-
glycyrrhetinate (22)
Acetobromolactose 15 (100 mg, 0.143 mmol), acceptor
4
(36 mg, 0.057 mmol), silver zeolite (ꢃ150 mg) and powdered 4 Å
molecular sieves (ꢃ100 mg) were suspended in dry CH2Cl2
(3 mL) and treated as described for 5 to afford 37 mg (57%) of 22
3.5.10. Allyl 3-O-[methyl (2,3,4-tri-O-acetyl-b-
uronate)]-18-b-glycyrrhetinate (25)
Bromide 16 (250 mg, 0.605 mmol), acceptor 11 (103 mg,
0.202 mmol), silver zeolite (ꢃ500 mg) and powdered 4 Å molecular
sieves (ꢃ200 mg) were suspended in dry CH2Cl2 (5 mL) and treated
D-glucopyranosyl-
as a colourless syrup. Rf 0.52 (1:1 n-hexane–EtOAc); ½a D20
ꢅ
+68.7
(c 0.3, CHCl3). lit5a
½
a 2D0
+65.6 (c 0.1, CH2Cl2). NMR data were iden-
ꢅ
tical to published values.5a

1070
Maria Carmen del Ruiz Ruiz et al. / Carbohydrate Research 344 (2009) 1063–1071
as described for 5 to give 92 mg (55%) of 25 as colourless syrup; Rf
1H NMR (CD3OD–CDCl3 ꢆ 5:1, 400 MHz): d 5.56 (s, 1H, H-12),
0.57 (3:2 n-hexane–EtOAc); ½a D20
ꢅ
+119 (c 0.4, CHCl3); 1H NMR
4.38 (d, 1H, J1 ,2 7.7 Hz, H-10), 3.82 (d, 1H, J4 ,5 9.7 Hz, H-50), 3.77
0
0
0
0
and 3.69 (2s, 6H, 60-OCH3, 30-OCH3), 3.52 (t, 1H, J3 ,4 9.3 Hz, H-
0
0
(CDCl3, 400 MHz): d 5.92 (ddd, 1H, CH2–CH@CH2), 5.64 (s, 1H, H-
12), 5.36–5.18 (m, 4H, CH2–CH@CH2, H-40, H-30), 5.05 (dd, 1H,
40), 3.35 (dd, 1H, J3 ,2 9.1 Hz, H-30), 3.23 (dd, 1H, H-20), 3.17 (br
dd, 1H, J 5.7, J 10.6 Hz, H-3), 2.68 (ddd, 1H, J 13.3 Hz, H-1a), 2.44
(s, 1H, H-9), 2.12 (dd, 1H, J 4.2, J 13.6 Hz, H-18), 2.00–0.90 (m,
17H, H-2a, H-2b, H-15a, H-16a, H-19a, H-21a, H-6a, H-7a, H-19b,
H-6b, H-7b, H-15b, H-21b, H-22a, H-22b, H-16b, H-1b), 1.41 (s,
3H, CH3-27), 1.14, 1.13 and 1.06 (3s, 12H, CH3-29, CH3-25, CH3-
26, CH3-23), 0.87 (s, 3H, CH3-24), 0.82 (s, 3H, CH3-28) and 0.79
(br d, 1H, H-5); 13C NMR (CD3OD–CDCl3 ꢆ 5:1): d 202.67 (C-11),
178.67 (C-30), 177.04 (C-60), 172.51 (C-13), 129.02 (C-12), 106.75
(C-10), 90.31 (C-3), 78.09 (C-50), 76.62 (C-30), 75.58 (C-20), 73.80
(C-40), 63.20 (C-9), 56.46 (C-5), 52.34 (OMe), 49.94 (OMe), 48.40
(C-18), 46.80 (C-8), 45.35 (C-20), 44.63 (C-14), 42.34 (C-19),
40.61 (C-4), 40.30 (C-1), 39.03 (C-22), 38.11 (C-10), 33.86 (C-7),
33.00 (C-17), 32.03 (C-21), 29.17 (C-28), 28.53 (C-29), 28.47 (C-
23), 27.58 (C-15), 27.40 (C-16), 26.89 (C-2), 23.83 (C-27), 19.31
(C-26), 18.46 (C-6), 17.03 (d.i., C-24, C-25). ESI-TOFMS: m/
z = 675.4529 [M+H]+; calcd 675.4108.
0
0
J4 ,5 8.0, J2 ,3 8.8 Hz, H-20), 4.65–4.54 (m, 3H, J1 ,2 8.0 Hz, H-10,
0
0
0
0
0
0
OCH2), 4.02 (d, 1H, J4 ,5 9.6 Hz, H-50), 3.75 (s, 3H, OCH3), 3.13 (dd,
1H, J 7.6, J 8.8 Hz, H-3), 2.79 (br d, 1H, J 13.6 Hz, H-3a), 2.31 (s,
1H, H-9), 2.13–1.78 (m, 16H, 3 ꢄ Ac, H-2a, H-2b, H-15a, H-16a,
H-18, H-19a, H-21a), 1.69–1.50 (m, 3H, H-6a, H-7a, H-19b), 1.46–
1.13 (m, 6H, H-6b, H-7b, H-15b, H-21b, H-22a, H-22b), 1.35 (s,
3H, CH3-27), 1.17, 1.12 and 1.11 (3s, 9H, CH3-29, CH3-25, CH3-
26), 0.93 (s, 3H, CH3-23), 1.05–0.88 (m, 2H, H-16b, H-1b), 0.80 (s,
3H, CH3-28), 0.77 (s, 3H, CH3-24) and 0.69 (br d, 1H, H-5); 13C
NMR (CDCl3): d 199.95 (C-11), 175.97 (C-30), 171.05 (60-C),
170.18, 169.28, 169.08, 168.97, 167.15 (COCH3, C-13), 132.18
(CH@CH2), 128.50 (C-12), 118.38 (CH@CH2), 102.78 (C-10), 90.42
(C-3), 72.38 (C-50), 72.17 (C-30), 71.46 (C-20), 69.46 (C-40), 65.00
(OCH2), 61.72 (C-9), 55.15 (C-5), 52.81 (60- OCH3), 48.25 (C-18),
45.32 (C-14), 43.96 (C-20), 43.12 (C-8), 41.05 (C-19), 39.17 (C-4),
38.99 (C-1), 37.67 (C-22), 36.74 (C-10), 32.68 (C-7), 31.78 (C-17),
31.10 (C-21), 28.47 (C-29), 28.32 (C-28), 27.68 (C-23), 26.43 (C-
16), 26.36 (C-15), 25.58 (C-2), 23.33 (C-27), 20.76, 20.59, 20.48,
20.42 (CH3CO), 18.63 (C-26), 17.32 (C-6), 16.32 and 16.28 (C-24,
C-25). ESI-TOFMS: m/z = 827.4896 [M+H]+; calcd 827.4581.
0
0
3.7. Methyl 3-O-(b-D-glucopyranosyluronic acid)-18-b-
glycyrrhetinate (28)
A solution of 27 (25 mg, 0.037 mmol) in MeOH (2 mL) was
treated with 0.2 M methanolic NaOH solution (2 mL) at 0 °C for
3 h. The solution was treated with DOWEX-50 H+ resin and was
filtered. The filtrate was concentrated and lyophilized from diox-
ane to afford 28 (22 mg, 91%) as off-white powder; Rf 0.32 (10:1
3.5.11. Benzyl 3-O-[methyl (2,3,4-tri-O-acetyl-b-
uronate)]-18-b-glycyrrhetinate (26)
D-glucopyranosyl-
Bromide 16 (250 mg, 0.605 mmol), acceptor 12 (113 mg,
0.202 mmol), silver zeolite (ꢃ500 mg) and powdered 4 Å molecu-
lar sieves (ꢃ200 mg) were suspended in dry CH2Cl2 (5 mL) and
were processed as described for 5 to furnish 95 mg (54%) of 26
MeCN–H2O);
½
a 2D0
ꢅ
ꢀ66.7 (c 0.3, MeOH); 1H NMR (CD3OD,
300 MHz): d 5.56 (s, 1H, H-12), 4.34 (d, 1H, J1 ,2 7.7 Hz, H-10),
3.69 (s, 3H, OCH3), 3.56–3.19 (m, 5H, H-30, H-40, H-50, H-20, H-
3), 2.69 (ddd, 1H, J 13.5 Hz, H-1a), 2.45 (s, 1H, H-9), 2.12 (dd,
1H, J 4.5, J 13.6 Hz, H-18), 2.00–0.90 (m, 17H, H-2a, H-2b, H-
15a, H-16a, H-19a, H-21a, H-6a, H-7a, H-19b, H-6b, H-7b,
H-15b, H-21b, H-22a, H-22b, H-16b, H-1b), 1.41 (s, 3H, CH3-27),
1.21, 1.15 and 1.14 (3s, 9H, CH3-29, CH3-25, CH3-26), 1.07 (s,
3H, CH3-23), 0.82 (s, 3H, CH3-24), 0.87 (s, 3H, CH3-28) and 0.79
(br d, 1H, H-5); 13C NMR (CD3OD): d 202.63 (C-11), 178.66 (C-
30), 176.67 (C-60), 172.45 (C-13), 129.03 (C-12), 106.76 (C-10),
90.29 (C-3), 78.085 (C-50), 76.66 (C-30), 75.58 (C-20), 73.79 (C-40),
63.21 (C-9), 56.48 (C-5), 52.34 (OCH3), 48.19 (C-18), 46.80 (C-8),
45.35 (C-20), 44.65 (C-14), 42.37 (C-19), 40.61 (C-4), 40.31 (C-
1), 39.04 (C-22), 38.13 (C-10), 33.88 (C-7), 33.00 (C-17), 32.06
(C-21), 29.18 (C-28), 28.54 and 28.48 (C-29, C-23), 27.61 (C-15),
27.42 (C-16), 26.91 (C-2), 23.85 (C-27), 19.35 (C-26), 18.47 (C-
6), and 17.03 (d.i., C-24, C-25). ESI-TOFMS: m/z = 661.4556
[M+H]+; calcd 661.3951.
0
0
as a colourless solid; Rf 0.43 (3:2 n-hexane–EtOAc), ½a D20
ꢀ59.7
ꢅ
(c 0.35, CHCl3); 1H NMR (CDCl3, 400 MHz): d 7.40–7.31 (m, 5H,
H-Ar), 5.54 (s, 1H, H-12), 5.28–5.07 (m, 4H, H-30, H-40, CH2Ph),
5.05 (dd, 1H, J3 ,2 9.2 Hz, H-20), 4.59 (d, 1H, J1 ,2 7.6 Hz, H-10),
0
0
0
0
4.01 (d, 1H, J4 ,5 9.6 Hz, H-50), 3.75 (s, 3H, OCH3,), 3.11 (dd, 1H,
J 6.4, J 9.9 Hz, H-3), 2.79 (ddd, 1H, J 13.6 Hz, H-1a), 2.28 (s, 1H,
H-9), 2.13–1.76 (m, 16H, 3 ꢄ Ac, H-2a, H-2b, H-15a, H-16a, H-
18, H-19a, H-21a), 1.69–1.50 (m, 3H, H-6a, H-7a, H-19b), 1.46–
1.13 (m, 6H, H-6b, H-7b, H-15b, H-21b, H-22a, H-22b), 1.33 (s,
3H, CH3-27), 1.18, 1.16 and 1.14 (3s, 9H, CH3-29, CH3-25, CH3-
26), 0.92 (s, 3H, CH3-23), 1.05–0.88 (m, 2H, H-16b, H-1b), 0.76
(s, 3H, CH3-24), 0.73 (s, 3H, CH3-28) and 0.69 (br d, 1H, H-5);
13C NMR (CDCl3): d 199.92 (C-11), 176.16 (C-30), 170.26 (C-60),
169.32, 169.00, 168.92, 167.18 (COCH3, C-13), 136.10 (C-arom.),
128.64, 128.53, 128.46, 128.15, 127.84, 127.26 (C-arom., C-12),
102.82 (C-10), 90.47 (C-3), 76.72 (CHPh2), 72.44 (C-50), 72.20 (C-
30), 71.49 (C-20), 69.48 (C-40), 66.22 (CH2Ph), 61.72 (C-9), 55.19
(C-5), 52.86 (OMe), 48.17 (C-18), 45.31 (C-14), 44.31 (C-20),
43.10 (C-8), 41.06 (C-19), 39.20 (C-4), 39.04 (C-1), 37.62 (C-22),
36.75 (C-10), 32.70 (C-7), 31.75 (C-17), 31.15 (C-21), 28.39 (C-
29), 28.28 (C-28), 27.71 (C-23), 26.44 (C-16), 26.37 (C-15), 25.60
(C-2), 23.30 (C-27), 20.67, 20.64, 20.52 (CH3CO), 18.65 (C-26),
17.36 (C-6), 16.35 and 16.31 (C-24, C-25). ESI-TOFMS: m/
z = 877.4055 [M+H]+; calcd 877.4738.
0
0
3.8. 3-O-(Methyl b-D-glucopyranosyluronate)-18-b-
glycyrrhetinic acid (29)
A solution of 24 (90 mg, 0.103 mmol) in a mixture of dry MeOH
(5 mL) and EtOAc (2 mL) was hydrogenated in the presence of 10%
Pd–C (10 mg) for 12 h at atmospheric pressure at rt. After comple-
tion of the reaction, the catalyst was removed by filtration through
a pad of CeliteÒ and washed with MeOH. The combined filtrates
were concentrated to give a colourless syrup (75 mg, 93%) which
was used without any further purification. The syrup was dis-
solved in dry MeOH (4 mL) and 0.1 M NaOMe solution (1 mL)
was added dropwise under ice cooling. The reaction mixture was
stirred at rt for 5 h until the deacylation was complete. The solu-
tion was treated with DOWEX-50 H+ resin, filtered and the resin
was washed with MeOH. The filtrate was concentrated and the
residue was lyophilized from dioxane to afford 29 as a white
3.6. Methyl 3-O-(methyl b-D-glucopyranosyluronate)-18-b-
glycyrrhetinate (27)
To a stirred solution of 23 (92 mg, 0.115 mmol) in dry MeOH
(5 mL) 0.1 M NaOMe solution (0.9 mL) was added dropwise under
ice cooling. The temperature of the reaction was raised to rt and
the reaction mixture was stirred for 3 h. The solution was neutral-
ized by the addition of DOWEX-50 H+ resin, filtered and the filtrate
was concentrated in vacuo to afford 27 (73 mg, 93%) as off-white
powder; Rf 0.67 (5:1 EtOAc–MeOH); ½a D20
ꢅ
+63.4 (c 0.33, MeOH);
amorphous solid (61 mg, 97%); Rf 0.78 (1:1 EtOAc–MeOH); ½a D20
ꢅ

Maria Carmen del Ruiz Ruiz et al. / Carbohydrate Research 344 (2009) 1063–1071
1071
+72 (c 0.27, MeOH); 1H NMR (CD3OD–CDCl3 ꢆ 5:1, 400 MHz): d
Acknowledgements
5.62 (s, 1H, H-12), 4.42 (d, 1H, J1 ,2 7.6 Hz, H-10), 3.83 (d, 1H, J4 ,5
0
0
0
0
9.7 Hz, H-50), 3.79 (s, 3H, OCH3), 3.56 (t, 1H, J3 ,4 9.3 Hz, H-40),
0
0
The authors are grateful to Daniel Kolarich and Martin Pabst for
providing the MS data. Financial support by Zentrum für Innova-
tion und Technologie (ZIT) is gratefully acknowledged.
3.39 (t, 1H, J3 ,2 9.2 Hz, H-30), 3.30 (dd, 1H, H-20), 3.19 (dd, 1H, J
5.6, J 10.8 Hz, H-3), 2.71 (ddd, 1H, J 13.6 Hz, H-1a), 2.42 (s, 1H,
H-9), 2.21 (dd, 1H, J 13.2, J 4.0 Hz, H-18), 2.16–0.90 (m, 17H, H-
2a, H-2b, H-15a, H-16a, H-19a, H-21a, H-6a, H-7a, H-19b, H-6b,
H-7b, H-15b, H-21b, H-22a, H-22b, H-16b, H-1b), 1.43 (s, 3H,
CH3-27), 1.19 and 1.16 (3s, 9H, CH3-29, CH3-25, CH3-26), 1.10 (s,
3H, CH3-23), 0.86 (s, 3H, CH3-24), 0.83 (s, 3H, CH3-28) and 0.81
(br d, 1H, H-5); 13C NMR (CD3OD–CDCl3 ꢆ 5:1): d 202.61 (C-11),
180.41 (C-30), 172.80 (C-60), 171.36 (C-13), 128.94 (C-12), 107.02
(C-10), 90.75 (C-3), 77.53 (C-30), 76.66 (C-50), 75.29 (C-20), 73.18
(C-40), 63.12 (C-9), 56.40 (C-5), 52.78 (OCH3), 49.85 (C-18),
46.75 (C-8), 44.91 (C-20), 44.62 (C-14), 42.44 (C-19), 40.52 (C-4),
40.19 (C-1), 39.03 (C-22), 38.07 (C-10), 33.80 (C-7), 32.98 (C-17),
32.02 (C-21), 29.19 (C-28), 28.76 (C-29), 28.8 (C-23), 27.60
(C-15), 27.40 (C-16), 26.98 (C-2), 23.82 (C-27), 19.29 (C-26),
18.43 (C-6), 16.96 and 16.93 (C-24, C-25). ESI-TOFMS: m/z =
661.4347 [M+H]+; calcd 661.3951.
0
0
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.carres.2009.04.015.
References
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3.9. 3-O-(b-D-Glucopyranosyluronic acid)-18-b-glycyrrhetinic
acid (30)
A solution of 29 (33 mg, 0.05 mmol) in dry MeOH (3 mL) was
stirred with 0.2 M methanolic NaOH (2 mL) for 3 h at rt. The solu-
tion was treated with DOWEX-50 H+ cation-exchange resin. The re-
sin was filtered off and the filtrate was concentrated and finally
lyophilized to afford 30 as white amorphous powder (30 mg,
91%); Rf 0.44 (1:2 EtOAc–MeOH); ½a D20
ꢅ
ꢀ40.6 (c 0.26, MeOH); 1H
NMR (CD3OD–CDCl3 ꢆ 5:1, 400 MHz): d 5.65 (s, 1H, H-12), 4.38
(d, 1H, J1 ,2 7.6 Hz, H-10), 3.81 (d, 1H, J4 ,5 9.6 Hz, H-50), 3.54 (t,
0
0
0
0
1H, J3 ,4 9.6 Hz, H-40), 3.67 (t, 1H, J3 ,2 9.2 Hz, H-30), 3.27 (dd, 1H,
H-20), 3.22–3.16 (m, 1H, H-3), 2.69 (ddd, 1H, J 13.6 Hz, H-1a),
2.43 (s, 1H, H-9), 2.21 (dd, 1H, J 13.2, J 4.0 Hz, H-18), 2.16–0.90
(m, 17H, H-2a, H-2b, H-15a, H-16a, H-19a, H-21a, H-6a, H-7a, H-
19b, H-6b, H-7b, H-15b, H-21b, H-22a, H-22b, H-16b, H-1b), 1.42
(s, 3H, CH3-27), 1.18 and 1.14 (3s, 9H, CH3-29, CH3-25, CH3-26),
1.07 (s, 3H, CH3-23), 0.87 (s, 3H, CH3-24), 0.84 (s, 3H, CH3-28)
and 0.78 (br d, 1H, H-5); 13C NMR (CD3OD–CDCl3 ꢆ 5:1,): d
202.60 (C-11), 180.26 (C-30), 172.59 (C-60), 171.18 (C-13), 128.84
(C-12), 106.83 (C-10), 90.66 (C-3), 77.45 (C-30), 76.42 (C-50), 75.02
(C-20), 72.93 (C-40), 62.96 (C-9), 56.27 (C-5), 46.60 (C-8),
44.73 (C-20), 44.43 (C-14), 42.23 (C-19), 40.38 (C-4), 40.09 (C-1),
38.83 (C-22), 37.89 (C-10), 33.67 (C-7), 32.82 (C-17), 31.88
(C-21), 29.14 (C-28), 28.76 (C-29), 28.31 (C-23), 27.44 (C-15),
27.26 (C-16), 26.82 (C-2), 23.83 (C-27), 19.34 (C-26), 18.27 (C-6),
16.92 and 16.86 (C-24, C-25). ESI-TOFMS: m/z = 647.3355
[M+H]+; calcd 647.3795.
0
0
0
0