A straightforward access to neohesperidose from naringin by acetolysis. Comparative behaviour of some flavonoid neohesperidosides and rutinosides under acetolysis

Article abstract of DOI:10.1016/j.tet.2013.12.064

A straightforward semisynthesis of neohesperidose was performed in three-steps with 43% overall yield starting from naringin, the main flavonoid of grapefruit. In addition, the behaviour of two pairs of flavonoid 7-O-rhamnoglucosides (neohesperidosides naringin and rhoifolin; rutinosides hesperidin and diosmin) under same acetolysis conditions was compared. Results demonstrated the crucial influence of the oxidation state of the aglycone (flavanone or flavone), and of the nature of the disaccharidic moiety on the course of the reaction.

Full text of DOI:10.1016/j.tet.2013.12.064

Tetrahedron 70 (2014) 1492e1496
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
A straightforward access to neohesperidose from naringin by
acetolysis. Comparative behaviour of some flavonoid
neohesperidosides and rutinosides under acetolysis
*
Guy Lewin
ꢀ
ꢀ
Laboratoire de Pharmacognosie (Univ. Paris-Sud BIOCIS UMR-8076 CNRS LabEx LERMIT), Faculte de Pharmacie, av. J.B. Clement,
^
92296 Chatenay-Malabry Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
A straightforward semisynthesis of neohesperidose was performed in three-steps with 43% overall yield
starting from naringin, the main flavonoid of grapefruit. In addition, the behaviour of two pairs of fla-
vonoid 7-O-rhamnoglucosides (neohesperidosides naringin and rhoifolin; rutinosides hesperidin and
diosmin) under same acetolysis conditions was compared. Results demonstrated the crucial influence of
the oxidation state of the aglycone (flavanone or flavone), and of the nature of the disaccharidic moiety
on the course of the reaction.
Received 19 November 2013
Received in revised form 18 December 2013
Accepted 23 December 2013
Available online 31 December 2013
Keywords:
Neohesperidose
Acetolysis
Naringin
Ó 2013 Published by Elsevier Ltd.
Flavonoids
Rutinose
OH
1. Introduction
6
O
O
HO
HO
O
O
HO
1'
1
R1
2
1
H3C
HO
O
OH
HO
R2
Neohesperidose 1 or 2-O-alpha-L-rhamnopyranosyl-D-gluco-
OH
1'
HO
H3C
HO
pyranose is a disaccharide present in the glycosidic moiety of var-
ious phenolic compounds, especially naringin 2, a bitter flavanone
glycoside, which is the main flavonoid of grapefruit (and pomelo).
In 1963, Horowitz and Gentili established the structure of 1 and
O
OH
HO
OH
3
R = H
1
1
R1= H R2 = OH (anomer α)
R1= OH R2 = H (anomer β)
showed that it was an isomer of rutinose 3 or 6-O-alpha-
L-rham-
nopyranosyl-
D
-glucopyranose.1 They also discovered that the
presence of the neohesperidosyl moiety was closely related on the
one hand to the bitterness of naringin and other flavanone glyco-
sides, and on the other hand to the sweeter character of the derived
dihydrochalcones (neohesperidin dihydrochalcone or NHDC 4,
a sweetener discovered during the 1960s has its origin in this last
observation).2 More recently, Kato et al. reported the insulinomi-
metic activity of 1, which promotes glucose uptake in the cultured
L6 skeletal muscle cells.3 As a result, the same group screened 14
other disaccharides for this activity and they identified three active
compounds, trehalose, isomaltose and gentiobiose, which dis-
played this insulin mimetic activity, but to a lesser extent than 1.4
So the potential pharmacological interest of 1 led us to research
the previously reported access to this compound in the literature.
5'
OH
O
4'
OH
6'
O
O
HO
HO
8
O
O
2
O
3'
7
9
1'
2'
6
3
H3C
HO
10
OH
4
5
HO
OH
2
OH
O
OCH3
OH
O
HO
HO
OH
O
O
O
H3C
HO
OH
HO
OH
4
* Tel.: þ33 146835593; fax: þ33 146835399; e-mail address: guy.lewin@u-psud.fr.
0040-4020/$ e see front matter Ó 2013 Published by Elsevier Ltd.
http://dx.doi.org/10.1016/j.tet.2013.12.064

G. Lewin / Tetrahedron 70 (2014) 1492e1496
1493
Most methods proceed by KoenigseKnorr reaction (modifica-
tion of Helferich)5 between 1,3,4,6-tetra-O-acetyl-
-glucopyr-
anose (prepared from
-glucose in 28e40% yield)5,6 and 2,3,4-tri-O-
acetyl- -rhamnosyl bromide (prepared from -rhamnose in 49%
yield).7 An approach, which involved a Schmidt glycosylation8 be-
tween 1-O-acetyl-3,4,6-tri-O-benzyl- -glucopyranose (prepared
from commercial 3,4,6-tri-O-acetyl- -glucal in 35% yield) and 2,3,4-
tri-O-acetyl- -rhamnosyl trichloroacetoimidate (prepared from
2,3,4-tri-O-acetyl-
naringin 2) along with
L
-rhamnose tetraacetate 7 and
D
-glucose
a
-
D
pentaacetate 8 (11.5% each from 2) as minor compounds. 1H NMR
D
spectra of these acetylated sugars (integration of the signals of
anomeric protons) proved 6, 7 and 8 to be mixtures of a/b anomers
in 85/15, 86/14 and 83/17 ratios, respectively.
a-
L
L
D
D
L
5'
L
-rhamnopyranose in 61% yield) was also de-
OAc
4'
OAc
6'
scribed.3 After removal of the various protecting groups, neo-
O
AcO
8
O
O
2
O
3'
7
AcO
9
hesperidose was recovered in low yields overall (12% for
1'
O
2'
crystallized
-neohesperidose from 3,4,6-tri-O-acetyl-D
-glucal3). Two semi-
b-neohesperidose from D
-glucose;6,9 9% for a mixture
6
3
H3C
AcO
O
10
4
5
a
/b
OAc
AcO
syntheses of 1 starting from naringin 2 were also reported in the
OAc
literature, which proceeded under ozonolysis, according to the
5
9
2,3-dihydro
2,3-dehydro rhoifolin octaacetate (flavone)
naringin octaacetate (flavanone)
10
ꢁ
method of Mester and Zemplen, (experimental conditions, scale
and yield not specified)11 or hydrothermolysis (heating in H2O at
120 ꢀC for 45 h, 27% yield), respectively.12 Consequently, the rather
modest yields in neohesperidose using chemical methods, as well
as the lack of any described enzymatic hydrolysis as an alternative
access, prompted us to investigate the chemical reactivity of nar-
ingin, which could constitute a cheap and easily available raw
material, potentially worthy of interest for an easy access to
neohesperidose.
OAc
OAc
O
AcO
O
O
O
AcO
OAc
OAc
10 apigenin 7-O-β-glucoside hexaacetate
2. Results and discussion
The acid hydrolysis of 2 could not be considered for the reason
that former studies rather showed, under various experimental
conditions (HCl 0.5 N or 10% aqueous AcOH), the preferential re-
activity of the sugaresugar bond compared to the sugareaglycone
linkage.13 Alkaline hydrolysis, a quite rare alternative to acid hy-
drolysis,14 was not possible with 2 either because of the resistance of
the b-glucosyleaglycone bond under basic conditions (Horowitz
and Gentili had first observed the resistance of this bond,1 and re-
lated it to the lack of assistance to displacement of the phenolate as
a consequence of the absence of a C-2 hydroxy group on glucosyl
moiety).15 Acetolysis, another method for the cleavage of O-glyco-
sidic bonds, has been used for a long time, especially for the struc-
tural elucidation of polysaccharides, because it preferentiallyattacks
(1/6) glycosidic linkages.16,17 In 1974, Rosenfeld and Ballou com-
pared kinetics of the acetolysis of several disaccharides and con-
firmed the faster cleavage of (1/6) glycosidic linkages over (1/4),
(1/3) and (1/2).18 This rather weak reactivity of the (1/2) gly-
cosidic linkage towards acetolysis and, surprisingly enough, the rare
occurrence of reported acetolysis of flavonoid glycosides in the lit-
erature led us to start this study.19 Firstly, naringin octaacetate 5 was
submitted to acetolysis under five experimental conditions: (a) in
10:9:1 v/v/v Ac2OeAcOHeH2SO4 at 20 ꢀC; (b) in 10:9:1 v/v/v
Ac2OeAcOHeH2SO4 at 45 ꢀC; (c) in 10:9:1 v/v/v Ac2OeAcOHeTFA at
20 ꢀC; (d) in 10:9:1 v/v/v Ac2OeAcOHeTFA at 45 ꢀC; (e) in 10:9:1 v/v/
v Ac2OeAcOHeTFA at 65 ꢀC. Monitoring of the reactions was carried
out by TLC analysis of Et2O extracts of previously neutralized sam-
ples. After 72 h under conditions (a) or 75 min under conditions (b),
reactions went almost to completion and displayed the same thin
layer chromatograms. On the contrary, the replacement of H2SO4 by
TFA was ineffective since no reaction occurred by using conditions
(c), (d) and (e) during 72 h, 3 h and 25 h, respectively. Thus we ap-
plied the acetolysis conditions (a) to naringin 2 (10 mmol) by using
one-pot sequential acetylation/acetolysis reactions. The Et2O extract
of the medium (previously diluted with water and neutralized)
provided a mixture having the same TLC profile as preliminary tests
(a) and (b), while a subsequent extraction of the aqueous phase with
n-BuOH led to a complex mixture (very polar substances with a UV
chromophore), which was not studied. The purification of the Et2O
extract mainly provided neohesperidose heptaacetate 6 (45% from
From neohesperidose heptaacetate 6, neohesperidose 1 was
recovered in almost quantitative yield (96%) by transesterification.
The 1H NMR spectrum of 1 (registered after 15 min in D2O, un-
changed after 10 h) displayed a 77/23 a/b anomers mixture. In or-
der to study the influence of the aglycone moiety on acetolysis, we
submitted the flavone rhoifolin octaacetate 9 (¼2,3-dehydro-nar-
ingin octaacetate) to the same (a) conditions. Compound 9 behaved
very differently from 5 since it was mostly recovered (53%) along
with small amounts of 10, apigenin 7-O-b-glucoside hexaacetate (in
10% yield) and 7, resulting from the incomplete acetolysis of the
only rha (1/2) glc linkage. The study was then continued in the 7-
O-rutinosyl series with acetolysis of the flavanone hesperidin
octaacetate 11 and the corresponding flavone, diosmin octaacetate
12. Their reactivity confirmed the known preferential cleavage of
(1/6) glycosidic linkages on the one hand, and the observed re-
sults with 5 and 9 on the other hand: so, the flavanone 11 did not
provide rutinose heptaacetate at all, but only the same equi-
molecular mixture of a- and b-peracetylated rhamnose and glucose

1494
G. Lewin / Tetrahedron 70 (2014) 1492e1496
as isolated from 5, while the flavone 12 gave, as major compounds,
diosmetin 7-O- -glucoside hexaacetate 13 (40%) and rhamnose
tetraacetate 7 through acetolysis of the rha (1/6) glc linkage only.
With flavanones 5 and 11, the cleavage of the b-glucosyl-agly-
b
cone bond can result from the formation of an intermediary qui-
none methide (with or without assistance of oxygen of the
pyranoglucosyl). A subsequent nucleophilic addition of an acetate
on the carbocation C-1 of the glucosyl unit mainly produces the
OCH3
O
O
AcO
a
anomer (known to be the more stable in the D-glucose series
H3C
AcO
O
O
O
O
AcO
2
3
because of the trans configuration of substituents at C-1 and C-
5);18 with flavones 9 or 12, the electrophilic attack on the oxygen
of the carbonyl group certainly leads to the stabilized benzopyri-
lium species, thus preventing a possible assistance to the cleavage
of the osidic bond. The comparison of the behaviour of neo-
hesperidosides (5, 9) and rutinosides (11, 12) fully confirms pref-
erential acetolysis of the (1/6) linkage: in the flavanone series, 11
[(1/6) linkage] released only the mixture of acetylated mono-
saccharides 7 and 8 free from rutinose heptaacetate, while 5
[(1/2) linkage] led mainly to the acetylated disaccharide 6 along
with 7 and 8 as minor products [we noticed with 5 that (1/2)
OAc
OAc
AcO
OAc
OAc
11 2,3-dihydro
12 2,3-dehydro
hesperidin octaacetate (flavanone)
diosmin octaacetate (flavone)
OAc
OCH3
OAc
O
AcO
AcO
O
O
O
OAc
linkage acetolysis was concomitant with
b-glucosyleaglycone
OAc
cleavage, and not subsequent, because the ratio 6/7e8 remains
constant when the time reaction is longer (4 h) under (b) condi-
tions]. For the same reason, in the flavone series, rutinoside 12
13 diosmetin 7-O-β-glucoside hexaacetate
provided as major compound the b-glucoside 13 resulting from an
easy cleavage of the (1/6) linkage, while neohesperidoside 9 was
almost inert under the same acetolysis conditions. Lastly, whereas
2.1. Mechanism of acetolysis
anomerization was mainly observed for acetolysis of the
eaglycone linkage, -rhamnose tetraacetate was mostly re-
covered without inversion of configuration at C-1, since the
anomer already displayed the trans configuration of substituents
b-glu-
Comparison of the reactions carried out on the two pairs of
flavanones (5, 11)-flavones (9, 12) in the series neohesperidosyl (5,
9) and rutinosyl (11, 12) clearly demonstrates that acetolysis of the
a-L
a
b-glucoside bond with aglycone occurs only with flavanones (Table
at C-1 and C-5.
1). This difference in reactivity could be explained by an initial
electrophilic attack of the acetylium cation (the assumed attacking
species),18 neither on the oxygen of the pyranose (mechanism of
Lindbergs) nor on the oxygen of the glycosidic bond (mechanism of
Lemieux),16 but rather on the C-4 carbonyl group of the aglycone
(Scheme 1).
3. Conclusion
In this study, from the largely available citroflavonoid naringin,
by-product of the fruit juice industry, we have reported a very
Table 1
Comparative behaviour of two pairs of 7-O-rhamnoglucosides under acetolysisa
Compound
Naringin octaacetate 5
(flavanone)
Rhoifolin octaacetate 9
(flavone)
Hesperidin octaacetate 11
(flavanone)
Diosmin octaacetate 12
(flavone)
Series
Neohesperidosyl
Total
Rutinosyl
Total
Cleavage of the
aglyconeeglucose bond
Cleavage of the
Lacking
Partial
Lacking
Total
Partial
Total
glucoseerhamnose bond
Products of acetolysis
isolated from the apolar phaseb
Neohesperidose
heptaacetate 6 45%
Starting
D
-Glucose
pentaacetate 8 31%
-Rhamnose
tetraacetate 7 31%
Diosmetin glucoside
hexaacetate 13 42%
compound 9 54%
Apigenin glucoside
hexaacetate 10 10%
D
-Glucose
pentaacetate 8 11%
-Rhamnose
tetraacetate 7 11%
L
L-Rhamnose
tetraacetate 7 40%
L
L-Rhamnose
tetraacetate 7 10%
a
10:9:1 v/v/v Ac2OeAcOHeH2SO4 at 20 ꢀC for 72 h.
Yields after purification by chromatography.
b
straightforward semisynthesis of neohesperidose, a disaccharide
whose insulinomimetic properties were recently discovered.
Starting from this result, we also studied three other flavonoid
glycosides for a significant reaction in the field of carbohydrate
chemistry, acetolysis, which surprisingly had almost never been
applied to this important phytochemical group. We were then able
to demonstrate how the oxidation state of the aglycone (flavanone
or flavone), and the nature of the disaccharidic moiety (neo-
hesperidose or rutinose, two isomeric rhamnoglucosides fre-
quently encountered in this class of polyphenols) could change the
course of the reaction.
b
a
O
O
peracetylated osidic moiety
a
b
a
OAc
flavanones
(5, 11)
flavones
(9, 12)
a
b
cleavage
no cleavage
Scheme 1. Hypothetical first intermediate structure formed during acetolysis.

G. Lewin / Tetrahedron 70 (2014) 1492e1496
1495
4. Experimental
moiety 92.5 (C-1), 77.6 (C-2), 73.6 (C-3); rhamnosyl moiety 98.7 (C-
10); other signals (not assigned) : 72.7, 68.6, 67.2 ppm. HRMS calcd
for [MþNa]þ C26H36O17Na 643.1850, found 643.1847.
4.1. General experimental procedures
Optical rotation measurement was conducted using an Optical
Activity PolAAr 32 polarimeter. 1H and 13C NMR spectra were
recorded in deuterated chloroform (CHCl3 as internal standard at
4.4.
L
-Rhamnose tetraacetate
The
a/b
ratio: 86/14 was inferred from 1H NMR spectrum of the
d
7.26 and 77.0 ppm) and in D2O (H2O as internal standard at
4.79 ppm; residual MeOH as internal standard at 49.5 ppm) on
equimolecular mixture -glucose pentaacetatee -rham-
nose tetraacetate isolated by flash chromatography [integration of
characteristic signals of H-1 ( and anomers) at 6.02 ppm
(J¼1.8 Hz) and 5.84 ppm (J¼1.5 Hz), respectively].
a/
b-
D
a/b-L
d
a Bruker AC-300 (300 MHz) or a Bruker AM-400 (400 MHz) in-
struments; NOESY, COSY and 1He13C (HMQC and HMBC) experi-
ments were performed with a Bruker AM-400. Mass spectra (MS)
and High Resolution Mass Spectra (HRMS) were recorded on
a Waters Micromass LCT Premier time-of-flight (TOF) mass spec-
trometer with electrospray ionization (ESI). Flash chromatogra-
phies were performed with silica gel 60 (9385 Merck) and
preparative TLC with 60F254 silica gel (5715 Merck).
a
b
4.4.1. d 6.02
-Rhamnose tetraacetate. 1H NMR (CDCl3, 300 MHz)
a
-L
(1H, d, J¼1.8 Hz, H-1), 5.25e5.34 (2H, m, H-2 and H-3), 5.13 (1H, t,
J¼9.9 Hz, H-4), 3.90e3.99 (1H, m, H-5), 1.25 (3H, t, J¼6.3 Hz, H-6);
acetyl groups 2.18, 2.17, 2.07, 2.02 (12H, 4s) ppm. HRMS calcd for
[MþNa]þ C14H20O9Na 355.1005, found 355.1002.
4.2. One-pot sequential acetylation/acetolysis of naringin 2
4.5.
D-Glucose pentaacetate
A solution of naringin (97% purity, 600 mg, 1 mmol) in 10 mL of
pyridineeAc2O (9:1) was left at 20 ꢀC for 24 h, heated at 60 ꢀC for
2 h, then evaporated under vacuum to dryness. The residue was
dissolved in Ac2O (20 mL), added at 0 ꢀC with 20 mL of
AcOHeH2SO4 (18:2), then the mixture was kept at room temper-
ature for 72 h. The solution was diluted with iced water (750 mL),
treated with 5 N aqueous NaOH (50 mL) and extracted five times
with Et2O (1 L in all). The organic layer was washed four times with
water, dried over Na2SO4, filtered and evaporated. The dried residue
(544 mg) was purified by flash chromatography on silica gel
(CH2Cl2eacetone 97:3) to give neohesperidose heptaacetate 6
The
a/b
ratio: 83/17 was inferred from 1H NMR spectrum of the
equimolecular mixture -glucose pentaacetatee -rham-
nose tetraacetate isolated by flash chromatography [integration of
characteristic signals of H-1 ( and anomers) at 6.34 ppm
(J¼3.6 Hz) and 5.72 ppm (J¼8.1 Hz), respectively].
a/
b-
D
a/b-L
a
b
4.5.1. Mixture
a/b-D
-glucose pentaacetate. 1H NMR (CDCl3,
300 MHz) 6.34 (d, J¼3.6 Hz, anomer ) and 5.72 (d, J¼8.1 Hz,
anomer ) and 5.26 (m, anomer ),
), H-1, 5.47 (t, J¼9.9 Hz, anomer
H-3, 5.08e5.18 (2H, m, H-2 and H-4), 4.25e4.33 (1H, m, H-6),
4.08e4.16 (1H, m, H-6), 4.08e4.16 (m, anomer ) and 3.85e3.90 (m,
d
a
b
a
b
(278 mg of
equimolecular amorphous mixture (165 mg, 23% from 2) of
rhamnose tetraacetate ( 86/14 mixture) 7 and -glucose pen-
taacetate ( 83/17 mixture) 8. Preparative TLC on silica gel
(CH2Cl2eEtOAc 90:10) of an aliquot (20 mg) of this mixture led to
isolation of pure -rhamnose tetraacetate (5 mg) and of 83/17
-glucose pentaacetate (6 mg) as amorphous compounds.
a/
b
85/15 amorphous mixture, 45% from 2) and an
a
L-
anomer b), H-5; acetyl groups 1.81e2.25 (15H) ppm. HRMS calcd
a
/b
D
for [MþNa]þ C16H22O11Na 413.1060, found 413.1067.
a/b
4.6. Transesterification of neohesperidose heptaacetate 6
a-
L
a/b
D
A solution of 6 (100 mg, 0.16 mmol) in 5 mL of MeONa 0.2 M waþs
left at 20 ꢀC for 2 h, then treated with AmberliteÔ IR120 (in H
form) till neutralization. Filtration then concentration under vac-
uum to dryness provided pure neohesperidose (51 mg, 96%) as an
amorphous white residue.
4.3. Neohesperidose heptaacetate 6
ratio: 85/15 was inferred from 1H NMR spectrum (in-
The a/b
tegration of characteristic signals of H-1 and H-3 of glucosyl tri-
acetate moiety).
4.7. Neohesperidose 1
4.3.1.
400 MHz)
a
-Neohesperidose heptaacetate signals. 1H NMR (CDCl3,
glucosyl moiety 6.30 (1H, d, J¼3.7 Hz, H-1), 5.45 (1H, t,
d
The a/b ratio: 77/23 was inferred from the integration of char-
J¼9.9 Hz, H-3), 5.0e5.08 (1H, m, H-4), 4.29 (1H, dd, J¼12.6 and
4.1 Hz, H-6), 4.06e4.11 (1H, m, H-5), 4.03e4.07 (1H, m, H-6), 3.93
(1H, dd, J¼9.9 and 3.7 Hz, H-2); rhamnosyl moiety 5.10e5.15 (1H,
m, H-30), 5.0e5.08 (2H, m, H-20 and H-40), 4.88 (1H, d, J¼1.4 Hz, H-
10), 3.78e3.85 (1H, m, H-50), 1.18 (3H, t, J¼6.2 Hz, H-60); acetyl
groups 2.24, 2.13, 2.09, 2.08, 2.04, 2.03, 1.98 (21H, 7s) ppm. 13C NMR
acteristic signals of H-10 and 3H-60 of rhamnosyl moiety in the 1H
NMR spectrum (registered at 20 ꢀC after 15 min in D2O, unchanged
after 10 h).
4.7.1.
a d 5.35 (d,
-Neohesperidose signals. 1H NMR (D2O, 400 MHz)
J¼3.7 Hz, H-1), 4.99 (d, J¼1.4 Hz, H-10), 4.11 (m, H-20), 3.55 (dd,
(CDCl3, 100 MHz) d glucosyl moiety 90.1 (C-1), 75.3 (C-2), 71.4 (C-3),
J¼9.8 and 3.7 Hz, H-2), 1.32 (d, J¼6.3 Hz, 3H-60) ppm. 13C NMR (D2O,
69.8 (C-5), 67.4 (C-4), 61.5 (C-6); rhamnosyl moiety 99.0 (C-10), 70.6
(C-40), 70.0 (C-20), 68.2 (C-30), 67.9 (C-50), 17.3 (C-60); acetyl groups
170.5, 170.2, 170.0 (2), 169.7, 169.6, 169.2 (CH3CO2e); 20.9, 20.8 (2),
20.7 (2C), 20.56 (2C) (CH3CO2e) ppm.
100 MHz) d
103.2 (C-10), 92.1 (C-1), 80.7 (C-2), 72.5 (C-4 and C-5),
71.7 (C-3), 70.7 (ꢁ2), 70.2 and 69.9 (C-20, C-30, C-40 and C-50), 61.2
(C-6), 17.2 (C-60) ppm.
4.7.2.
b d 5.12 (d,
-Neohesperidose signals. 1H NMR (D2O, 400 MHz)
4.3.2.
distinguishable from the corresponding
could be assigned): 1H NMR (CDCl3, 400 MHz)
b
-Neohesperidose heptaacetate signals. (only those which are
-anomer signals, and
glucosyl moiety
J¼1.5 Hz, H-10), 4.74 (d, J¼7.8 Hz, H-1), 4.08e4.10 (m, H-20),
a
4.00e4.05 (m, H-50), 3.60e3.65 (m, H-3), 3.34e3.37 (m, H-2), 1.29
d
(d, J¼6.3 Hz, 3H-60) ppm. 13C NMR (D2O, 100 MHz)
d
101.9 (C-10),
5.67 (1H, d, J¼8.1 Hz, H-1), 5.27 (1H, t, J¼9.5 Hz, H-3), 4.99e5.04
(1H, m, H-4), 3.75e3.82 (1H, m, H-2); rhamnosyl moiety 4.90 (1H,
d, J¼1.8 Hz, H-10), 1.17 (3H, t, J¼6.2 Hz, H-60); acetyl groups 2.14,
95.4 (C-1), 81.4 (C-2), 76.9 (C-3), 76.4 (C-4), 72.6, 70.9, 70.8 and 70.0
(C-5, C-20, C-30 and C-40), 69.5 (C-50), 61.3 (C-6), 17.0 (C-60) ppm. All
the other 1H NMR signals (not assigned) between 3.92e3.75 and
3.53e3.45 ppm. HRMS calcd for [MþNa]þ C12H22O10Na 349.1111,
2.10, 2.07, 2.02, 1.96 (5s) ppm. 13C NMR (CDCl3, 100 MHz)
d glucosyl

1496
G. Lewin / Tetrahedron 70 (2014) 1492e1496
20
20
found 349.1106. [
a]
ꢂ5.3 (after 15 min in H2O, c 1.5) [lit. [
a]
J¼8.8 Hz, H-50), 6.98 (1H, d, J¼2.4 Hz, H-8), 6.67 (1H, d, J¼2.4 Hz,
H-6), 6.52 (1H, s, H-3), 3.91 (3H, s, OCH3-40), 2.43 (3H, s, OCOCH3-
5), 2.36 (3H, s, OCOCH3-30); glucose moiety: 5.28e5.35 (2H, m, H-
200 and 300), 5.23 (1H, d, J¼7.6 Hz, H-100), 5.14e5.19 (1H, m, H-400),
4.19e4.30 (2H, m, 2H-600), 3.97e4.01 (1H, m, H-500), 2.08, 2.07,
2.06, 2.04 (12H, 4s, four acetyl groups) ppm. 13C NMR (CDCl3,
D
D
20
ꢂ3.9 (after 7 min in H2O, c 3);6
[a
]
ꢂ5.4 (c 1, H2O)20].
D
4.8. Acetolysis of rhoifolin octaacetate 9
Rhoifolin octaacetate (18.5 mg, 0.02 mmol) was dissolved in
Ac2O (1.2 mL), added at 0 ꢀC with 1.2 mL of AcOHeH2SO4 (9:1), then
the mixture was kept at room temperature for 72 h. A same work-
up as described with naringin octaacetate (but with CH2Cl2 instead
of Et2O) led to a dried residue (14 mg). Purification by preparative
thin layer chromatography on silica gel (CH2Cl2eMeOH 98.5:1.5)
100 MHz)
d [aglycone moiety] 176.1 (C-4), 161.3 (C-2), 159.9 (C-7),
158.2 (C-9), 154.1 (C-40), 150.7 (C-5), 140.2 (C-30), 125.3 (C-60),
123.7 (C-10), 120.9 (C-20), 112.8 (C-10), 112.5 (C-50), 109.2 (C-6),
107.6 (C-3), 102.7 (C-8), 56.1 (OCH3-40), 21.1 (OCOCH3-5), 20.6
(OCOCH3-30); glucose moiety : 98.1 (C-100), 72.5 and 72.4 (C-300, C-
500), 70.9 (C-200), 68.1 (C-400), 62.0 (C-600), 20.6 (OCOCH3-200, 300, 400,
600); other signals (OCOCH3) : 170.5, 170.1, 169.5, 169.4, 169.2,
168.7 ppm. HRMS calcd for [MþNa]þ C34H34O17Na 737.1694,
found 737.1693.
allowed recovery of 9 (10 mg, 54%) and isolation of apigenin 7-O-b-
glucoside hexaacetate 10 (1.3 mg, 10%); rhamnose tetraacetate
(z0.6 mg, 10%), was identified by the same Rf and colour with
H2SO4eanisaldehyde spray reagent as 7.
4.9. Apigenin 7-O-b-glucoside hexaacetate 10
Acknowledgements
1H NMR (CDCl3, 400 MHz)
d
[aglycone moiety] 7.86 (2H, d,
J¼8.7 Hz, H-20 and 60), 7.25 (2H, d, J¼8.7 Hz, H-30 and 50), 7.00 (1H, d,
J¼2.4 Hz, H-8), 6.69 (1H, d, J¼2.4 Hz, H-6), 6.58 (1H, s, H-3), 2.44
(3H, s, OCOCH3-5), 2.34 (3H, s, OCOCH3-30) ppm; glucose moiety: cf.
We thank K. Leblanc for MS and HRMS measurements, J.-C.
Jullian for NMR experiments and A. Pearson for English correc-
tions of the manuscript.
diosmetin 7-O-b
-glucoside hexaacetate. 13C NMR (CDCl3, 100 MHz)
d
[aglycone moiety] 161.5 (C-2),160.0 (C-7),158.3 (C-9),153.0 (C-40),
151.0 (C-5), 128.5 (C-10), 127.5 (C-20 and 60), 122.4 (C-30 and 50), 112.9
Supplementary data
(C-10), 109.4 (C-6), 108.6 (C-3), 102.7 (C-8), 21.1 (OCOCH3-40 and
OCOCH3-5) ppm; glucose moiety : cf. diosmetin 7-O-
b
-glucoside
Copies of 1H and 13C NMR spectra with assignments of signals.
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.tet.2013.12.064.
hexaacetate; signal of C-4 not detected. HRMS calcd for [MþNa]þ
C33H32O16Na 707.1588, found 707.1580.
4.10. Acetolysis of hesperidin octaacetate 11
References and notes
Same acetolysis conditions and work-up as described with 9
(but with Et2O instead of CH2Cl2) were used with hesperidin
octaacetate (19 mg, 0.02 mmol). The dried residue was purified on
silica gel (CH2Cl2eMeOH 98.5:1.5) to give the same equimolecular
1. Horowitz, R. M.; Gentili, B. Tetrahedron 1963, 19, 773e782.
2. Horowitz, R. M.; Gentili, B. J. Agric. Food Chem. 1969, 17, 696e700.
3. Yamasaki, K.; Hishiki, R.; Kato, E.; Kawabata, J. ACS Med. Chem. Lett. 2011, 2,
17e21.
4. Yamasaki, K.; Hishiki, R.; Kato, E.; Kawabata, J. Biosci. Biotechnol. Biochem. 2012,
76, 841e842.
mixture (9 mg, 62%) of
L
-rhamnose tetraacetate (
a
/b
86/14) 7 and D-
glucose pentaacetate (a/b
83/17) 8 as obtained from 2.
5. Helferich, B.; Zirner, J. Chem. Ber. 1962, 95, 2604e2611.
6. Koeppen, B. H. Tetrahedron 1968, 24, 4963e4966.
7. Fischer, E.; Bergmann, M.; Rabe, A. Ber. 1920, 53, 2362e2388.
8. Schmidt, R. R.; Michel, J. Angew. Chem., Int. Ed. Engl. 1980, 19, 731e732.
9. Koeppen, B. H. Tetrahedron Lett. 1968, 2393e2394.
10. Zemplen, G.; Bognar, R.; Mester, L. Ber. Deut. Chem. Ges. 1942, 75B, 488e495.
11. Horowitz, R. M.; Gentili, B.; Hand, E. S. In I.U.P.A.C International Symposium on the
Chemistry of Natural Products; 1964; pp 158e159 Kyoto, Japan, Abstracts of Papers;
http://ci.nii.ac.jp/naid/110006801617/en.
12. Kim, Y. C.; Higuchi, R.; Komori, T. Liebigs Ann. Chem. 1992, 575e579.
13. Chandler, B. V.; Harper, K. A. Aust. J. Chem. 1961, 14, 586e595.
14. Quintin, J.; Lewin, G. Tetrahedron Lett. 2005, 46, 4341e4343.
15. Ballou, C. E. Adv. Carbohydr. Chem. 1954, 9, 59e95.
4.11. Acetolysis of diosmin octaacetate 12
Same acetolysis conditions and work-up as described with 9
were used with diosmin octaacetate (28 mg, 0.03 mmol). The dried
residue was purified on silica gel (CH2Cl2eMeOH 98:2) and gave
mainly pure amorphous diosmetin 7-O-
(9 mg, 42%) and -rhamnose tetraacetate (4 mg of the mixture
85/15 according to its 1H NMR spectrum, 40%).
b-glucoside hexaacetate 13
L
a/
b
16. Guthrie, R. D.; McCarthy, J. F. Adv. Carbohydr. Chem. 1967, 22, 11e23.
17. Bedini, E.; Comegna, D.; Di Nola, A.; Parrilli, M. Tetrahedron Lett. 2008, 49,
2546e2551.
4.12. Diosmetin 7-O-b-glucoside hexaacetate 13
18. Rosenfeld, L.; Ballou, C. E. Carbohydr. Res. 1974, 32, 287e298.
19. Sakushima, A.; Nishibe, S. Phytochemistry 1988, 27, 915e919.
20. Kamiya, S.; Esaki, S.; Hama, M. Agric. Biol. Chem. 1967, 31, 261e266.
1H NMR (CDCl3, 400 MHz)
d [aglycone moiety] 7.70 (1H, dd,
J¼8.8 and 2 Hz, H-60), 7.54 (1H, d, J¼2 Hz, H-20), 7.06 (1H, d,