Synthesis of N,N′-diglycosylated isoindigos

Article abstract of DOI:10.1039/c2ob25866h

The first N,N′-diglycosylated isoindigos were prepared by P(NEt ₂)₃-mediated dimerization of acetyl protected N-glycosyl-5-alkylisatins. Subsequent deacetylation yielded the corresponding deprotected N,N′-diglycosylated isoindigos. I

Full text of DOI:10.1039/c2ob25866h

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Synthesis of N,N’-Diglycosylated Isoindigos
Dennis Kleeblatt,a Baraa Siyo,a Martin Hein,a Viktor Iaroshenko,a,b Jamshed Iqbal,c Alexander
Villinger,a Peter Langer* a,d
a Institut für Chemie, Universität Rostock, Albert-Einstein-Str. 3a, 18059 Rostock, Germany
b National Taras Shevchenko University, 62 Volodymyrska st., Kyiv-33, 01033, Ukraine
c Department of Pharmacy, COMSATS Institute of Information Technology, Abbottabad, Postal Code
22060, Pakistan
d Leibniz-Institut für Katalyse e. V. an der Universität Rostock, Albert-Einstein-Str. 29a, 18059
Rostock, Germany
Fax: +49 (381)4986412, E-mail: peter.langer@uni-rostock.de
Abstract: The first N,N’-diglycosylated isoindigos were prepared by P(NEt2)3-mediated
dimerization of acetyl protected N-glycosyl-5-alkylisatins. Subsequent deacetylation yielded the
corresponding deprotected N,N’-diglycosylated isoindigos. Isatine-N-glycosides containing an
unsubstituted or alkyl-substituted heterocyclic moiety and β-
D
-manno- and β-
L-rhamno configured
carbohydrate substituents were successfully transformed into the corresponding isoindigos. In
contrast, isatins with β-
D
-gluco- or β-
D-xylo configured substituents failed to give the desired
products.
Keywords: indigoids, isoindigo, carbohydrates, heterocycles, phosphorous
Introduction
Glycosylated indoles show remarkable pharmacological activity against diverse malignant tumor
cells.1,2 Indigo, indirubin, and isoindigo contain a bis-indole framework and can be found in a number
of natural products. In 2002, Laatsch et al. reported the isolation of the akashines A, B, and C from
terrestric Streptomyces sp. GW48/1497.3 In contrast to the pharmacologically inactive non-
glycosylated indigo, the akashines exhibit a considerable growth inhibitory activity toward various
human tumor cell lines. Indirubin, the red isomer of indigo, is the active ingredient of the traditional

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chinese medicinal recipe Danggui Longhui Wan, which has been used for the treatment of myelocytic
leukemia.4 This substance and its substituted derivatives are potent inhibitors of several kinases, such
as glycogen synthase kinase-3 (GSK-3) and cyclin-dependent kinases (CDKs).5,6 Among these
inhibitors, the bis-indole indirubin and its analogues have gathered considerable attention, as they were
discovered to inhibit CDKs and GSK-3. For example, 5-substituted indirubins display high inhibitory
potency toward various CDKs and GSK-3β. Several O- and N-glycosylated indigoid dyes were
synthesized in recent years7. Most of the compounds studied so far exhibit higher anti-proliferative
activity toward human cancer cells in vitro than their non-glycosylated analogues. Notably, both
deprotected and protected N-glycosides are pharmacologically relevant. For example, the biological
activity of so called ‘Natura’, i. e. acetyl-protected β-D-xylopyranosyl-N-isoindigo, was reported to be
higher than that of its deprotected analogue.8,9,10
We previously reported the synthesis of indigo-N-glycosides, indirubin-N-glycosides and
heteroananlogues of N-glycosylated indigoid dyes.11 Herein, we report what is, to the best of our
knowledge, the first synthesis of isoindigo-N,N’-diglycosides.
Results and Discussion
Mono-glycosylated isoindigos were prepared by Sassatelli et al. in 2005 by condensation of isatin-N-
glycosides with oxindole.8 N-Glycosylated oxindoles are, in contrast to isatin-N-glycosides, not readily
available. Therefore, our strategy for the synthesis of hitherto unknown N,N’-diglycosylated isoindigos
relies on the reductive dimerization of isatin-N-glycosides. The starting materials were prepared
following known procedures. Acetylated N-(β-D-mannopyranosyl)- and N-(β-L-rhamnopyranosyl)
isatins 4(β) were obtained by condensation of
D-mannose (1a) or L-rhamnose (1b) with different
alkylated anilines to give 2(α,β) as an anomeric mixture, respectively. Subsequent acetylation of the
sugar moiety afforded 3(α,β) and the reaction with oxalyl chloride gave the cyclization products
4(α,β). The products exist as anomeric mixtures which mainly contain the β-anomers, while the α-
anomers are present only in small amount (Scheme 1, Table 1). The purification by column
chromatography allowed for the isolation of anomerically pure products 4(β) which, in some cases,
still contain small amounts of the corresponding α-isomers, due to the difficult separation (Scheme
1).12,13 The isolation of a pure α-anomer was only successful in the case of derivative 4e(α). The

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12-14
13,15
intermediate products 2
and 3
were directly employed for the next reaction step without
further purification, because they proved to be partly unstable in our hands. The yields of intermediates
3(α,β) over the 2 steps were in the range of 80-86 %. The corresponding isatin-N-glycosides of
galactose, -xylose and
-glucose were previously synthesized by us under similar conditions.13 The
D-
D
D
novel isatin-N-glycosides, which contain alkyl substituents located at the isatin moiety, were prepared
analogously starting with the commercially available alkylated anilines. It is worth to be noted, that the
yields of the cyclization reactions depended on the scale and varied over a wide range (Table 1).
R2
O
R2
O
OR1
OH
HN
N
OR1
OR1
OH
O
i
iii
O
O
OR1
OH
OR1 OR1
OH OH
OR1
OR1
ii
4a-d
1a-d
2a-d
3a-d
R2
O
R2
O
OH
HN
N
OR1
OR1
OR1
OH
OH
O
i
iii
O
O
OR1
Me
Me
Me
OR1
ii
OH
OR1
2e-i
3e-i
4e-i
1e-i
2: R1 = H, 3, 4: R1 = Ac 2, 3, 4: R2= H, Me, Et, i-Pr, t-Bu
Scheme 1. Synthesis of acetyl protected N-(β-
D
-mannopyranosyl)- and N-(β-
L-
rhamnopyranosyl)isatins. Reagents and conditions: (i) EtOH (abs.), R2NH2, 78°C, 12 h; (ii) pyridine,
Ac2O, 0°C, 24 h; (iii) oxalyl chloride, AlCl3, 55°C, 1.5 h, then chromatographic separation of the
anomeric isomers.
Table 1. Yields of isatin-N-glycosides 4a-i
R1
R2
Yield
4

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(%)a
21
2,3,4,6-tetra-O-acetyl-
2,3,4,6-tetra-O-acetyl-
2,3,4,6-tetra-O-acetyl-
2,3,4,6-tetra-O-acetyl-
D
D
D
D
-mannopyranosyl H
a
b
c
d
e
f
-mannopyranosyl CH3
20
-mannopyranosyl CH(CH3)2 59
-mannopyranosyl C(CH3)3
63
23
47
95
2,3,4-tri-O-acetyl-
2,3,4-tri-O-acetyl-
2,3,4-tri-O-acetyl-
2,3,4-tri-O-acetyl-
2,3,4-tri-O-acetyl-
L-rhamnopyranosyl
L-rhamnopyranosyl
L-rhamnopyranosyl
L-rhamnopyranosyl
L-rhamnopyranosyl
H
CH3
C2H5
g
h
i
CH(CH3)2 80
C(CH3)3 64
a Yields of isolated products
The determination of the anomeric configuration of products 4a-i was carried out on the basis of our
previous investigations13 of the structures of N-(2,3,4-tri-O-acetyl-
-rhamnopyranosyl)isatin (4e(α,β))
and N-(2,3,4,6-tetra-O-acetyl-β- -mannopyranosyl)isatin (4a(β)) which both exist as anomeric
mixtures. Usually, the anomers of rhamno and manno configured glycosides are difficult to distinguish
L
D
1
on the basis of H-NMR coupling constants, because the J1’,2’ coupling constants are relatively small
3
for both anomers. However, in the 1H-NMR spectrum of isatine-N-rhamnosides 4e(α,β) the α-anomer
3
shows a relatively large coupling constant of J1’,2’ = 5.7 Hz (presumably due to a change of the
conformation of the carbohydrate moiety),13 whereas the β-anomer shows the expected small value of
3J1’,2’ = 1.5 Hz. The assignment of the anomers was possible based on NOESY-experiments and,
independently, by X-ray crystal structure analyses.13 In a NOESY-experiment, the expected
correlations of the signals of H-1’ with those of H-3’ and H-5’ could be observed for compound 4e(β).
A similar structural proof was carried out for isatine-N-mannosides 4a(β).13 The determination of the
anomeric configuration of the novel isatine-N-mannosides 4b-d and isatine-N-rhamnosides 4f-i was
carried out by comparison of their chemical shifts and coupling constants with those of mannoside
4a(β) and rhamnoside 4e(β), respectively. The values are not significantly influenced by the presence
of substituents located at the aromatic ring.
The dimerization of the isatin-N-glycosides was realized following the conditions developed by
Bogdanov and coworkers.16 To a dichloromethane solution of the isatin-N-glycoside was rapidly added
tris(diethylamino)phosphine at –78 °C and the reaction mixture was slowly warmed to 20 °C. The

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dimerizations of various glycosylisatines, containing a β-D-mannose or a β-L-rhamnose moiety, gave
the acetyl-protected dimers 5a-i in good to very good yield (Schemes 2 and 3, Tables 2 and 3).
The deacetylation of 5a-i was carried out under basic conditions (Zemplén conditions) and gave the
deprotected isoindigo-N,N’-diglycosides 6a-i as solids in moderate to good yield (Schemes 2 and 3,
Tables 2 and 3).17 In nearly all cases, the deprotected products precipitated in the methanolic reaction
mixture and could be isolated by filtration. In case of the tert-butyl-substituted isoindigos, the products
are partly soluble in methanol and the products had to be purified by column-chromatography after
neutralization with acetic acid.
AcO
R2
R2
4
O
5
3a
3
O
AcO
6
2
7a
O
N
O
7
i
N1
O
AcO
AcO
O
1'
OAc
OAc
2'
OAc
O
N
3'
5'
6'
OAc
4'
OAc
R2
AcO
AcO
4a-d
OAc
5a-d
R2= H, Me, i-Pr, t-Bu
R2
OH
5
3'''
6
HO
OH
2'''
4
O
4'''
7
3a
ii
1'
2'
OH
1'''
5'''
7a
N
O
6'''
6''
3
3'
O
N
7a'
1''
2
3a'
1
HO
5''
7'
2''
O
4'
4''
6'
HO
OH
3''
5'
R2
OH
6a-d
Scheme 2. Synthesis of N,N’-di-(β-
D-mannopyranosyl)isoindigos 6a-d. Reagents and conditions: (i)
CH2Cl2, P(NEt2)3 (1.1 equiv.) -78°C→25°C; (ii) MeOH (abs), NaOMe.
Table 2. Synthesis of N,N’-di-(β-D-mannopyranosyl)isoindigos 5a-d
and 6a-d

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R2
Yield (5) (%)a Yield (6) (%)a
5,6
a
H
72
75
80
77
65
50
CH3
b
CH(CH3)2 65
c
C(CH3)3
65
d
a Yields of isolated products
R2
R2
H3C
4
O
5
3a
3
O
AcO
6
2
7a
O
N
O
7
i
N1
O
AcO
AcO
O
1'
OAc
2'
OAc
OAc
O
N
3'
6'
5'
H3C
OAc
4'
OAc
R2
AcO
CH3
4e-i
5e-i
R2= H, Me, Et, i-Pr, t-Bu
R2
OH
5
3'''
6
HO
OH
2'''
1'''
4
O
4'''
7
3a
ii
1'
2'
5'''
7a
N
O
CH3
6'''
6''
3
3'
H3C
O
N
7a'
1''
2
3a'
1
5''
7'
2''
O
4'
4''
6'
HO
OH
3''
5'
R2
OH
6e-i
Scheme 3. Synthesis of N,N’-di-(β-L-rhamnopyranosyl)isoindigos 6e-i. Reagents and conditions: (i)
CH2Cl2, P(NEt2)3 (1.1 equiv.) -78°C→25°C; (ii) MeOH (abs), NaOMe.

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Table 3. Synthesis of N,N’-di-(β-L-rhamnopyranosyl)isoindigos 5e-i and
6e-i
R2
Yield (5) (%)a
Yield (6) (%)a
5,6
H
68
89
83
80
78
84
72
81
78
50
e
f
CH3
CH2CH3
CH(CH3)2
C(CH3)3
g
h
i
a Yields of isolated products
The dimerization reactions of the isatin-N-glycosides derived from β-
D
-galactose, β- -glucose and β-
D
D-xylose failed. In these reactions a slow conversion of the starting material was observed by tlc, but
only an inseparable mixture of products could be isolated after aqueous work-up. Due to the
unsatisfactory results, we varied the reaction conditions. At first, the solvent was changed to prevent
any side-reactions of the reactive intermediate with dichloromethane. Toluene was chosen and the
reaction was carried out at -78 → 20°C. Then the temperature was increased. At first, the mixture was
stirred at 60 °C for three hours and finally the toluene solution was heated under reflux for three hours.
In all these experiments, it was not possible to isolate a clean product by column chromatography of
the crude products. Probably, follow-up reactions and decomposition reactions occur during
chromatography. The desired products (or other molecules) could also not be detected by HPLC-MS
and GC-MS experiments of the reaction mixtures.
The failure of the reactions of β-
trans configuration. In fact, the first three carbon atoms of β-
have the same relative configuration (1,2-trans; 1,3-cis), while the first three C-atoms of β-
and β- -rhamnose have a different relative configuration (1,2-cis; 1,3-cis). However, the exact reason
D
-galactose, β-
D
-glucose and β-
D
-xylose might be related to their 1,2-
-glucose and β- -xylose
-mannose
D-galactose, β-
D
D
D
L
of this effect remains unclear at present. During the dimerization, an interaction of the OAc-group of
the 1,2-trans configured sugars with the reactive (carbenoid) intermediate of the isatin moiety might
play an unfavourable role. To further study this hypothesis, the dimerization was also tried with the
1,2-trans configured α-anomer of 4e. However, we could not isolate the desired dimerization product

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or any other product from the complex reaction mixture. The desired product or other products could
also not be detected by analysis of the crude product mixture by 1H NMR or HPLC-MS.
Due to the symmetry of the products, a single set of signals was generally observed in the 1H- and 13C-
NMR-spectra of all products. 2D NMR-experiments, like NOESY, COSY and HSQC, confirmed the
structures as shown in Scheme 3. The central C=C double bond of isoindigo derivatives 5 and 6 was
assigned to have an E-configuration. The assignment is based on diagnostic downfield shifts observed
for proton resonances of H-4 (H-4’), which are comparable to those observed for the protons of related
isoindigo derivatives.8a,11d This downfield shift can be explained by the anisotropic effect of the
neighbouring carbonyl group. Our discussion, which is based on the chemical shift analysis, is
supported by the structural assignment and chemical shift analysis of the E- and Z-isomers of
structurally related 4,7,4’,7’-tetra-tert-butyl-1,1’-bis(acenaphtylenyliden-2-one).18 The E-configuration
was independently confirmed by X-ray crystal structure analyses of product 5f (Figure 1).19 We
previously reported that structurally related 3-(2-coumaranon-3-ylidene)-1-(2,3,4,6-tetra-O-acetyl-β-
D-mannopyranosyl)-oxindole also possesses an E-configuration.11d
Figure 1. ORTEP view of compound 5f. Displacement ellipsoids are drawn at the 50% probability
level.

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In conclusion, the first synthesis N,N’-diglycosylated isoindigo derivatives has been reported by
P(NEt2)3-mediated dimerization of readily available N-glycosylisatins and subsequent deacetylation.
The reactions are easy to carry out and proceed in high yields. The biological activity is currently
being studied and will be reported elsewhere.
Experimental section
General. All solvents were anhydrous and commercially available and all reactions were performed
1
under argon atmosphere. Yields refer to isolated products. H NMR spectra (250.13 MHz, 300.13
MHz and 500.13 MHz) and 13C NMR spectra (62.9 MHz, 75.5 MHz and 125.8 MHz) were recorded
on Bruker spectrometers AV 250, AV 300 and AV 500 in CDCl3 and DMSO-d6 as solvents. The
calibration of spectra was carried out on solvent signals (CDCl3: δ (1H) = 7.25, δ (13C) = 77.0; DMSO-
d6: δ (1H) = 2.50, δ (13C) = 39.7). For the NMR signals of the compounds 4a-i, 5a-i and 6a-i the atom
labelling given in scheme 2 was used. Mass spectrometric data (MS) were obtained by electron
ionization (EI, 70 eV), chemical ionization (CI, isobutane) or electrospray ionization (ESI). The mass
spectra and high-resolution mass spectra (HRMS) were recorded on the following MS instruments:
Time-of-Flight (LC / MS 6210 (Agilent Technologies) for ESI and Finnigan MAT 95 XP (Thermo
Electron Corporation) for EI / CI. Elemental analyses were performed on a C,H,N,S analyser (Thermo
Quest Flash EA 1112). The melting points were measured with a polarizing microscope (Leitz
Laborlux 12 Pol-S) equipped with a hot stage (Mettler FP 90). Thin layer chromatography was
performed on silica-gel foil (Merck DC-foil, silica gel 60, F254) and silica gel plates (Merck HPTLC
precoated plates, silica gel 60, F254) pursues. Detection was carried out via UV absorbance at 254 nm
or 366 nm and/or development with 10% methanolic sulfuric acid and subsequent heat treatment.
Column chromatography was performed on Macherey-Nagel silica gel 60 (particle size 63-200 nm,
70-230 mesh).
Synthesis of glycosylated anilines 2 and 3. The synthesis of these derivatives has been described in
the literature.12-15 We used the following modified procedure: The dried sugar (1 eq.) was refluxed
with the freshly distilled aniline derivative (1.1 eq.) in abs. ethanol (about 100 ml per 10 g of the sugar)
for 10-14 h in an argon atmosphere. Then, the mixture was cooled and stored over night in the
refrigerator. During this time, the product (2) precipitated and was then isolated by filtration. The
product was dried under vacuum and subsequently dissolved/ suspended in dry pyridin (1.8 eq. per

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free OH group of the sugar). After that, the mixture was cooled in an ice bath and acetic anhydride (1.5
eq. per free OH group of the sugar) was rapidly added under stirring. Stirring in the ice bath was
continued until all of the starting material had been dissolved (about 3 h). Then the mixture was stored
over night in the refrigerator. For work up, the mixture was poured onto ice-water and three times
extracted with ethyl acetate. The combined organic phases were washed with sodium
hydrogencarbonate solution, water and brine. After drying of the organic layer with sodium sulfate and
filtration, the solvent was removed under vacuum. Purification by flash column chromatography
(heptane/ ethyl acetate v:v = 4:1) yielded product 3 which was directly used for the next step.
Synthesis of glycosylated isatins 4. All isatin-N-glycosides were prepared by reaction of the acetyl
protected glycosylated anilines with oxalyl chloride in the presence of aluminium chloride as described
in the literature.12,13 The following procedure was applied: To a stirred solution of the acetylated
glycosyl aniline (1 eq.) in oxalyl chloride (about 10 eq.) an equivalent of anhydrous aluminium
chloride was added. The mixture was stirred for 1.5 hours at 55 °C (TLC control). Then, the excess of
oxalyl chloride was removed in vacuo. After cooling of the residue to 0 °C, ice water was added to the
solution with stirring. The yellow sugar precipitated. The mixture was extracted three times with
EtOAc, the combined organic layers were washed with a saturated aqueous solution of sodium
bicarbonate and with water and dried (Na2SO4). The solution was filtered, the filtrate was concentrated
under reduced pressure, and the residue was purified by column chromatography (silica gel, eluent:
heptane/ ethyl acetate). The data of 4a and 4e have been previously reported.12,13 The spectroscopic
data of the new compounds are listed below.
1-(2,3,4,6-Tetra-O-acetyl-ß-D-mannopyranosyl)-5-methylisatin (4b). Starting from the
corresponding aniline glycoside 3b (1.20 g, 2.7 mmol), 10 eq. of oxalyl chloride (3.50 g, 27.6 mmol),
and aluminum chloride (365 mg, 2.7 mmol), 4b could be isolated after column chromatography
1
(heptane/ ethyl acetate v:v = 6:1 → 3:1) as orange syrup (yield: 270 mg, 20%); H NMR (300 MHz,
3
3
CDCl3): δ = 7.39 (d (br), J7,6 = 8.3Hz, 1H, H-7), 7.36 (m, 1H, H-4), 7.33 (dd (br), J6,7 = 8.3Hz,
4J6,4 = 1.9Hz, 1H, H-6), 5.86 (d, 3J1’,2’ = 1.5Hz, 1H, H-1’), 5.56 (dd, 3J2’, 1’ = 1.5Hz, 3J2’, 3’ = 3.3Hz, 1H,
H-2’), 5.37 (dd, 3J4’,3’ ≈ 3J4’,5’ ≈ 10.0Hz, 1H, H-4’), 5.27 (dd, 3J3’,2’ = 3.3Hz, 3J3’,4’ = 10.2Hz, 1H, H-3’),
2
2
3
4.30 (dd, J6’a,6’b = 12.5Hz, 3J6’a,5’ = 5.2Hz, 1H, H-6’(a)), 4.18 (dd, J6’b,6’a = 12.5Hz, J6’b,5’ = 2.4Hz,
3
3
3
1H, H-6’(b)), 3.88 (ddd, J5’,4’ = 9.7Hz, J5’,6’a = 5.2Hz, J5’,6’b = 2.4Hz, 1H, H-5’), 2.29 (s (br), 3H,
CH3), 2.09, 2.07, 1.95, 1.87 (4s, 12H, 4*CH3COO). 13C NMR (63 MHz, CDCl3): δ = 181.9 (C-3),
170.3, 169.6, 169.5, 169.4 (4*CH3COO), 157.1 (C-2), 146.8 (C), 138.2 (C-6), 133.9 (C), 125.3 (C-4),
118.0 (C), 115.4 (C-7), 80.3 (C-1’), 75.4 (C-5’), 70.4 (C-3’), 70.0 (C-2’), 65.1 (C-4’), 62.1 (C-6’),

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20.7, 20.7, 20.6, 20.5, 20.4 (4*CH3COO, CH3). MS (EI, 70 eV): m/z (%) = 491 (6) [M]+; 449 (17); 331
(32); 289 (70); 229 (61); 169 (100); 127 (45); 109 (50). HRMS (EI): calcd. for C23H25NO11 [M]+
491.14221. Found 491.14212.
1-(2,3,4,6-Tetra-O-acetyl-ß-D-mannopyranosyl)-5-isopropylisatin (4c). Starting from the
corresponding aniline glycoside 3c (5.00 g, 10.7 mmol), 10 eq. of oxalyl chloride (13.60 g, 107.1
mmol), and aluminum chloride (1.43 g, 10.7 mmol), 4c could be isolated after column chromatography
1
(heptane/ ethyl acetate v:v = 6:1 → 3:1) as orange solid (3.30 g, 59%), mp 85-87°C; H NMR (300
3
5
MHz, CDCl3): δ = 7.47 (m, 1H, H-4), 7.42 (dd, J7,6 = 8.4Hz, J7,4 = 0.9Hz, 1H, H-7), 7.39 (dd,
4
3
3
3J6,7 = 8.4Hz, J6,4 = 1.7Hz, 1H, H-6), 5.86 (d, J1’,2’ = 1.6Hz, 1H, H-1’), 5.59 (dd, J2’, 1’ = 1.6Hz, 3J2’,
3
3
3’ = 3.4Hz, 1H, H-2’), 5.39 (dd, J4’,3’ ≈ 3J4’,5’ ≈ 10.0Hz, 1H, H-4’), 5.27 (dd, J3’,2’ = 3.4Hz, 3J3’,4’
2
2
= 10.2Hz, 1H, H-3’), 4.31 (dd, J6’a,6’b = 12.5Hz, 3J6’a,5’ = 5.3Hz, 1H, H-6’(a)), 4.19 (dd, J6’b,6’a
=
12.5Hz, 3J6’b,5’ = 2.4Hz, 1H, H-6’(b)), 3.88 (ddd, 3J5’,4’ = 9.9Hz, 3J5’,6’a = 5.3Hz, 3J5’,6’b = 2.4Hz, 1H, H-
5’), 2.87 (sept, 3JH,H = 6.9Hz, 1H, CH(CH3)2), 2.11, 2.08, 1.97, 1.88 (4s, 12H, 4*CH3COO), 1.22, 1.21
3
(2d, JH,H = 6.9Hz, 6H, CH(CH3)(a,b)). 13C NMR (63 MHz, CDCl3): δ = 182.0 (C-3), 170.4, 169.7,
169.5, 169.4 (4*CH3COO), 157.3 (C-2), 147.0, 145.2 (2*C), 136.2 (C-6), 122.8 (C-4), 118.1 (C),
115.5 (C-7), 80.4 (C-1’), 75.6 (C-5’), 70.4 (C-3’), 70.1 (C-2’), 65.1 (C-4’), 62.2 (C-6’), 33.4
(CH(CH3)2), 23.7 , 23.7 (CH(CH3)(a,b)), 20.8, 20.7, 20.7, 20.4 (4*CH3COO). Elemental analysis:
calcd. for C25H29NO11 (519.5): C, 57.80, H, 5.63, N, 2.70. Found C, 58.13, H, 6.00, N, 2.80. MS (EI,
70 eV): m/z (%) = 519 (21) [M] +; 331 (88); 271 (9); 229 (9); 188 (41); 169 (100); 139 (15); 127 (35);
+
109 (89). HRMS (ESI): calcd. for C25H30NO11 [M+H] 520.18134 and for C25H29NO11 [M+Na]
+
542.16328. Found 520.18223 and 542.16478.
1-(2,3,4,6-Tetra-O-acetyl-ß-D-mannopyranosyl)-5-(tert-butyl)isatin (4d). Starting from the
corresponding aniline glycoside 3d (5.00 g, 10.4 mmol), 10 eq. of oxalyl chloride (13.23 g, 104.2
mmol), and aluminum chloride (1.40 g, 10.5 mmol), 4d could be isolated after column
chromatography (heptane/ ethyl acetate v:v = 6:1 → 3:1) as orange solid (3.50 g, 63%), mp 88-90°C;
4
3
1H NMR (300 MHz, CDCl3): δ = 7.62 (d (br), J4,6 = 2.2Hz, 1H, H-4), 7.57 (dd, J6,7 = 8.5Hz,
3
3
4J6,4 = 2.2Hz, 1H, H-6), 7.43 (d (br), J7,6 = 8.5Hz, 1H, H-7), 5.86 (d, J1’,2’ = 1.6Hz, 1H, H-1’), 5.59
3
3
3
(dd, J2’,1’ = 1.6Hz, J2’,3’ = 3.3Hz, 1H, H-2’), 5.38 (dd, J4’,3’ ≈ 3J4’,5’ ≈ 10.0Hz, 1H, H-4’), 5.27 (dd,
2
3J3’,2’ = 3.3Hz, 3J3’,4’ = 10.2Hz, 1H, H-3’), 4.32 (dd, J6’a,6’b = 12.5Hz, 3J6’a,5’ = 5.4Hz, 1H, H-6’(a)),
2
3
3
3
4.19 (dd, J6’b,6’a = 12.5Hz, J6’b,5’ = 2.4Hz, 1H, H-6’(b)), 3.88 (ddd, J5’,4’ = 9.9Hz, J5’,6’a = 5.4Hz,
3J5’,6’b = 2.4Hz, 1H, H-5’), 2.11, 2.08, 1.97, 1.87 (4s, 12H, 4*CH3COO), 1.29 (s, 9H, C(CH3)3). 13C
NMR (63 MHz, CDCl3): δ = 182.1 (C-3), 170.4, 169.7, 169.5, 169.4 (4*CH3COO), 157.4 (C-2), 147.7,

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146.8 (2*C), 134.9 (C-6), 122.1 (C-4), 117.8 (C), 115.3 (C-7), 80.4 (C-1’), 75.6 (C-5’), 70.4 (C-3’),
70.1 (C-2’), 65.1 (C-4’), 62.2 (C-6’), 34.6 (C(CH3)3), 31.1 (C(CH3)3), 20.8, 20.8, 20.7, 20.4
(4*CH3COO). Elemental analysis: calcd. for C26H31NO11 (533.52): C, 58.53, H, 5.86, N, 2.63. Found:
C, 58.46, H, 6.34, N, 2.45. MS (EI, 70 eV): m/z (%) = 533 (11) [M]+; 331 (52); 271 (6); 202 (17); 169
(100); 127 (14); 109(45). HRMS (ESI): calcd. for C26H32NO11 [M+H]+ 534.19699 and for
C26H31NNaO11 [M+Na]+ 556.17893. Found 534.19690 and 556.17909.
1-(2,3,4,6-tetra-O-acetyl-ß-D-rhamnopyranosyl)-5-methylisatin (4f). Starting from the
corresponding aniline glycoside 3f. (1.30 g, 3.4 mmol), 10 eq. of oxalyl chloride (4.35 g, 34.3 mmol),
and aluminum chloride (455 mg, 3.4 mmol), 4f could be isolated after column chromatography
(heptane/ ethyl acetate v:v = 6:1 → 3:1) as orange solid (698 mg, 47%), mp 211-212°C; 1H NMR (300
MHz, CDCl3): δ = 7.42 (d (br), 3J7,6 = 8.2Hz, 1H, H-7), 7.37 (m, 1H, H-4), 7.33 (dd (br), 3J6,7 = 8.2Hz,
3
3
3
4J6,4 = 1.9Hz, 1H, H-6), 5.81 (d, J1’,2’ = 1.5Hz, 1H, H-1’), 5.55 (dd, J2’,1’ = 1.5Hz, J2’,3’ = 3.0Hz, 1H,
H-2’), 5.24-5.14 (m, 2H, H-3’, H-4´), 3.78-3.68 (m, 1H, H-5´), 2.30 (s (br), 3H, CH3), 2.08, 1.96, 1.88
(3s, 9H, 3*CH3COO), 1.33 (d, 3J6´,5´ = 6.2Hz, 3H, 3*H-6´). 13C NMR (63 MHz, CDCl3): δ = 182.0 (C-
3), 170.0, 169.6, 169.5 (3*CH3COO), 157.2 (C-2), 147.0 (C), 138.3 (C-6), 133.9 (C), 125.3 (C-4),
118.0 (C), 115.5 (C-7), 80.2 (C-1’), 74.1 (C-5’), 70.4, 70.4, 69.9 (C-2’, C-3’, C-4’), 20.8, 20.7
(2*CH3COO), 20.6 (CH3), 20.5 (CH3COO), 17.6 (C-6’). MS (EI, 70 e V): m/z (%) = 433 (17) [M]+,
273 (73), 162 (21), 153 (75), 111 (55), 83 (19). HRMS (EI): Calcd. for C21H23NO9 ([M+]) 433.13673.
Found 433.13685.
1-(2,3,4,6-tetra-O-acetyl-ß-
D-rhamnopyranosyl)-5-ethylisatin
(4g).
Starting
from
the
corresponding aniline glycoside 3g. (800 mg, 2.0 mmol), 10 eq. of oxalyl chloride (2.50 g, 19.7
mmol), and aluminum chloride (271 mg, 2.0 mmol), 4g could be isolated after column
chromatography (heptane/ ethyl acetate v:v = 6:1 → 3:1) as orange solid (864 mg, 95%), mp 201-
203°C; 1H NMR (250 MHz, DMSO-d6): δ = 7.54-7.45 (m, 2H, H-6, H-7), 7.38 (s (br), 1H, H-4), 6.10
3
(d, J1’,2’ = 1.4Hz, 1H, H-1’), 5.43 (dd, J3’,2’ = 3.5Hz, J3’,4’ = 10.0Hz, 1H, H-3’), 5.38 (dd,
3
3
3
3
3J2’,1’ = 1.4Hz, J2’,3’ = 3.5Hz, 1H, H-2’), 5.05 (dd, J4’,3’ ≈ 3J4’,5’ ≈ 10.0Hz, 1H, H-4´), 4.05 (dq,
3J5’,4’ = 9.8Hz, 3J5’,6’ = 6.2Hz, 1H, H-5´), 2.58 (q, 3JH,H = 7.6Hz, 2H, CH2CH3), 2.09, 1.94, 1.77 (3s, 9H,
3
3
3*CH3COO), 1.23 (d, J6´,5´ = 6.2Hz, 3H, 3*H-6´), 1.15 (t, JH,H = 7.6Hz, 3H, CH2CH3).
13C NMR (63 MHz, DMSO-d6): δ = 182.2 (C-3), 170.0, 169.8, 169.8 (3*CH3COO), 157.5 (C-2),
147.2, 139.3 (2*C), 137.2 (C-6), 123.3 (C-4), 118.3 (C), 115.7 (C-7), 79.7 (C-1’), 72.3, 70.2, 70.2,
69.7 (C-2’, C-3’, C-4’, C-5’), 27.4 (CH2CH3), 20.8, 20.7, 20.6 (3*CH3COO), 17.5 (C-6’), 15.7

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(CH2CH3). MS (EI, 70 e V): m/z (%) = 447 (16) [M]+, 273 (49), 176 (24), 153 (75), 111 (62), 83 (26).
HRMS (EI): Calcd. for C22H25NO9 ([M+]) 447.15238. Found 447.15329.
1-(2,3,4,6-tetra-O-acetyl-ß-D-rhamnopyranosyl)-5-isopropylisatin (4h). Starting from the
corresponding aniline glycoside 3h. (900 mg, 2.2 mmol), 10 eq. of oxalyl chloride (2.80 g, 22.1
mmol), and aluminum chloride (295 mg, 2.2 mmol), 4h could be isolated after column
chromatography (heptane/ ethyl acetate v:v = 6:1 → 3:1) as orange solid (815 mg, 80%), mp 129-
1
3
4
131°C; H NMR (300 MHz, CDCl3): δ = 7.46-7.43 (m, 2H, H-4, H-7), 7.39 (dd, J6,7 = 8.4Hz, J6,4
=
3
1.9Hz, 1H, H-6), 5.82 (d, 3J1’,2’ = 1.5Hz, 1H, H-1’), 5.56 (dd, J2’,1’ = 1.5Hz, 3J2’,3’ = 3.0Hz, 1H, H-2’),
3
5.25-5.14 (m, 2H, H-3’, H-4’), 3.78-3.69 (m, 1H, H-5’), 2.86 (sept, JH,H = 6.9Hz, 1H, CH(CH3)2),
3
2.08, 1.96, 1.87 (3s, 9H, 3*CH3COO), 1.33 (d, J6’,5’ = 6.2Hz, 3H, 3*H-6’), 1.21, 1.20 (2d,
3JH,H = 6.9Hz, 6H, CH(CH3)(a,b)). 13C NMR (63 MHz, CDCl3): δ = 182.2 (C-3), 170.0, 169.6, 169.5
(3*CH3COO), 157.4 (C-2), 147.2, 145.1 (2*C), 136.2 (C-6), 122.8 (C-4), 118.1 (C), 115.6 (C-7), 80.3
(C-1’), 74.1 (C-5’), 70.5, 70.4, 70.0 (C-2’, C-3’, C-4’), 33.4 (CH(CH3)2), 23.8, 23.7 (CH(CH3)(a,b)),
20.8, 20.8, 20.5 (3*CH3COO), 17.7 (C-6’). HRMS (ESI): Calcd. for C23H28NO9 ([M+H]+) 462.17586
and for C23H27NNaO9 ([M+Na]+) 484.15780. Found 462.17605 and 484.15832.
1-(2,3,4-tri-O-acetyl-ß-
L
-rhamnopyranosyl)-5-(tert-butyl)isatin
(4i).
Starting
from
the
corresponding aniline glycoside 3i (6.50 g, 15.4 mmol), 10 eq. of oxalyl chloride (19.30 g, 152.1
mmol), and aluminum chloride (2.00 g, 15.0 mmol), 4i could be isolated after column chromatography
1
(heptane/ ethyl acetate v:v = 6:1 → 3:1) as orange solid (4.70 g, 64%), mp 152-154°C; H NMR (250
3
MHz, CDCl3): δ = 7.61-7.56 (m, 2H, H-4, H-6), 7.45 (d (br), J7,6 = 8.3Hz, 1H, H-7), 5.82 (d,
3
3
3J1’,2’ = 1.5Hz, 1H, H-1’), 5.56 (dd, J2’,1’ = 1.5Hz, J2’,3’ = 3.0Hz, 1H, H-2’), 5.25-5.14 (m, 2H, H-3’,
3
H-4’), 3.79-3.69 (m, 1H, H-5’), 2.08, 1.96, 1.87 (3s, 9H, 3*CH3COO), 1.33 (d, J6’,5’ = 6.2Hz, 3H,
3*H-6’), 1.28 (s, 9H, C(CH3)3). 13C NMR (63 MHz, CDCl3): δ = 182.2 (C-3), 170.0, 169.6, 169.5
(3*CH3COO), 157.4 (C-2), 147.5, 146.9 (2*C), 134.9 (C-6), 122.0 (C-4), 117.8 (C), 115.3 (C-7), 80.2
(C-1’), 74.1 (C-5’), 70.4, 70.4, 69.9 (C-2’, C-3’, C-4’), 34.5 (C(CH3)3), 31.5 (C(CH3)3), 20.8, 20.7,
20.5 (3*CH3COO), 17.6 (C-6’). MS (EI, 70 e V): m/z (%) = 475 (20) [M]+; 273 (98); 258 (3); 213
(28); 171 (43); 153 (100); 129 (4); 111 (95). HRMS (ESI): Calcd. for C24H30NO9 [M+H]+ 476.19151
and for C24H29NNaO9 [M+Na]+ 498.17345. Found 476.19168 and 498.17355.
General procedure for the preparation of N,N’-di-glycosylated isoindigos 5a-i: The
corresponding glycosylated isatin (1 equiv.) was dissolved in dichloromethane (1 ml per 200 mg
glycosyl isatine) and cooled to -78°C. To the stirred solution tris(diethylamino)phosphine (1.1 equiv.)

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was rapidly added and the reaction mixture was allowed to warm to 25°C. When the reaction was
complete, the solvent was removed in vacuo and the residue was purified by column chromatography
(silica gel, heptanes / EtOAc v:v = 3:1).
1,1’-Di(2,3,4,6-tetra-O-acetyl-ß-
D
-mannopyranosyl)isoindigo
(5a).
Starting
from
the
corresponding glycosyl isatine 4a (400 mg, 0.84 mmol) and P(NEt2)3 (228 mg, 0.92 mmol), 5a could
be isolated after column chromatography as an orange brown solid (278 mg, 72%), mp 144-146°C;
3
4
1H NMR (250 MHz, CDCl3): δ = 8.98 (dd (br), J4,5 = 8.2Hz, J4,6 = 1.2Hz, 2H, H-4, H-4’), 7.49 (dd
3
(br), J7,6 = 8.1Hz, J7,5 = 1.2Hz, 2H, H-7, H-7’), 7.30 (ddd, J6,7 = 8.1Hz, J6,5 = 7.5Hz, J6,4 = 1.2Hz,
4
3
3
4
3
2H, H-6, H-6’), 7.03 (ddd, J5,6 = 7.5Hz, J5,4 = 8.2Hz, J5,7 = 1.2Hz, 2H, H-5, H-5’), 6.01 (d,
3
4
3
3
3J1’’,2’’ = 1.6Hz, 2H, H-1’’, H-1’’’), 5.61 (dd, J2’’,1’’ = 1.6Hz, J2’’,3’’ = 3.4Hz, 2H, H-2’’, H-2’’’), 5.42
3
3
(dd, J4’’,3’’ ≈ 3J4’’,5’’ ≈ 10.0Hz, 2H, H-4’’, H-4’’’), 5.29 (dd, J3’’,2’’ = 3.4Hz, 3J3’’,4’’ = 10.2Hz, 2H, H-
2
3’’, H-3’’’), 4.31 (dd, J6’’a,6’’b = 12.4Hz, 3J6’’a,5’’ = 4.9Hz, 2H, H-6’’(a), H-6’’’(a)), 4.23 (dd,
3
3
2J6’’b,6’’a = 12.4Hz, 3J6’’b,5’’ = 2.6Hz, 2H, H-6’’(b), H-6’’’(b)), 3.88 (ddd, J5’’,4’’ = 9.8Hz, J5’’,6’’a
3
= 4.9Hz, J5’’,6’’b = 2.6Hz, 2H, H-5’’, H-5’’’), 2.11, 2.08, 1.97, 1.86 (4s, 24H, 8*CH3COO). 13C NMR
(63 MHz, CDCl3): δ = 170.5, 169.7, 169.6, 169.5 (8*CH3COO), 166.7 (C-2, C-2’), 142.5 (C-7a, C-
7a’), 132.8 (C-3, C-3’), 132.1 (C-6, C-6’), 129.2 (C-4, C-4’), 122.5 (C-5, C-5’), 121.6 (C-3a, C-3a’),
113.3 (C-7, C-7’), 80.7 (C-1’’, C-1’’’), 75.6 (C-5’’, C-5’’’), 70.7 (C-3’’, C-3’’’), 69.9 (C-2’’, C-2’’’),
65.3 (C-4’’, C-4’’’), 62.3 (C-6’’, C-6’’’), 20.8, 20.7, 20.7, 20.5 (8*CH3COO). MS (EI, 70 eV): m/z (%)
= 922 (22) [M]+; 331 (25); 169 (100); 109 (64). HRMS (ESI): calcd. for C44H47N2O20 [M+H]+
923.27167. Found 923.2703.
1,1’-Di(2,3,4,6-tetra-O-acetyl-ß-D-mannopyranosyl)-5,5’-dimethylisoindigo (5b). Starting from
the corresponding glycosyl isatine 4b (400 mg, 0.81 mmol) and P(NEt2)3 (221 mg, 0.89 mmol), 5b
could be isolated after column chromatography as an orange brown solid (290 mg, 75%), mp 153-
4
155°C; 1H NMR (300 MHz, CDCl3): δ = 8.80 (d (br), J4,6 = 1.8Hz, 2H, H-4, H-4’), 7.36 (d,
3
4
3J7,6 = 8.2Hz, 2H, H-7, H-7’), 7.11 (dd (br), J6,7 = 8.2Hz, J6,4 = 1.8Hz, 2H, H-6, H-6’), 6.00 (d,
3
3
3J1’’,2’’ = 1.5Hz, 2H, H-1’’, H-1’’’), 5.59 (dd, J2’’,1’ = 1.5Hz, J2’’,3’’ = 3.4Hz, 2H, H-2’’, H-2’’’), 5.42
3
3
(dd, J4’’,3’’ ≈ 3J4’’,5’’ ≈ 10.0Hz, 2H, H-4’’, H-4’’’), 5.28 (dd, J3’’,2’’ = 3.4Hz, 3J3’’,4’’ = 10.2Hz, 2H, H-
2
3’’, H-3’’’), 4.29 (dd, J6’’a,6’’b = 12.4Hz, 3J6’’a,5’’ = 4.9Hz, 2H, H-6’’(a), H-6’’’(a)), 4.22 (dd,
3
3
2J6’’b,6’’a = 12.4Hz, 3J6’’b,5’’ = 2.6Hz, 2H, H-6’’(b), H-6’’’(b)), 3.86 (ddd, J5’’,4’’ = 9.9Hz, J5’’,6’’a
= 4.9Hz, 3J5’’,6’’b = 2.6Hz, 2H, H-5’’, H-5’’’), 2.35 (s (br), 6H, 2*CH3), 2.11, 2.08, 1.97, 1.88 (4s, 24H,
8*CH3COO). 13C NMR (75 MHz, CDCl3): δ = 170.5, 169.7, 169.6, 169.5 (8*CH3COO), 166.8 (C-2,
C-2’), 140.2 (C-7a, C-7a’), 132.9 (C-3, C-3’), 132.7 (C-6, C-6’), 131.8 (C-5, C-5’), 129.4 (C-4, C-4’),

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121.7 (C-3a, C-3a’), 113.0 (C-7, C-7’), 80.5 (C-1’’, C-1’’’), 75.5 (C-5’’, C-5’’’), 70.7 (C-3’’, C-3’’’),
70.0 (C-2’’, C-2’’’), 65.3 (C-4’’, C-4’’’), 62.3 (C-6’’, C-6’’’), 21.2, 20.8, 20.7, 20.7, 20.5
(8*CH3COO, 2*CH3). Elemental analysis: calcd. for C46H50N2O20 (950.89): C, 58.10; H, 5.30; N, 2.95.
Found: C, 58.11; H, 5.65; N, 2.86. MS (EI, 70 eV): m/z (%) = 950 (61.83) [M]+; 620 (10); 331 (18);
290 (19); 169 (100); 109 (71). HRMS (ESI): calcd. for C46H51N2O20 [M+H]+ 951.30297 and for
C46H50N2NaO20 [M+Na]+ 973.28491. Found 951.30297 and 973.28638.
1,1’-Di(2,3,4,6-tetra-O-acetyl-ß-D-mannopyranosyl)-5,5’-diisopropylisoindigo (5c). Starting from
the corresponding glycosyl isatine 4c (400 mg, 0.77 mmol) and P(NEt2)3 (210 mg, 0.85 mmol), 5c
could be isolated after column chromatography as an orange brown solid (251 mg, 65%), mp 143-
1
4
3
145°C; H NMR (250 MHz, CDCl3): δ = 8.91 (d, J4,6 = 1.8Hz, 2H, H-4, H-4’), 7.39 (d, J7,6 = 8.4Hz,
3
2H, H-7, H-7’), 7.17 (dd, 3J6,7 = 8.4Hz, 4J6,4 = 1.8Hz, 2H, H-6, H-6’), 6.01 (d, J1’’,2’’ = 1.5Hz, 2H, H-
3
3
3
1’’, H-1’’’), 5.60 (dd, J2’’,1’’ = 1.5Hz, J2’’,3’’ = 3.3Hz, 2H, H-2’’, H-2’’’), 5.42 (dd, J4’’,3’’ ≈ 3J4’’,5’’
3
≈ 10.0Hz, 2H, H-4’’, H-4’’’), 5.31 (dd, J3’’,2’’ = 3.3Hz, 3J3’’,4’’ = 10.2Hz, 2H, H-3’’, H-3’’’), 4.30 (dd,
2
2J6’’a,6’’b = 12.4Hz, 3J6’’a,5’’ = 5.0Hz, 2H, H-6’’(a), H-6’’’(a)), 4.21 (dd, J6’’b,6’’a = 12.4Hz, 3J6’’b,5’’
= 2.6Hz, 2H, H-6’’(b), H-6’’’(b)), 3.88 (ddd, 3J5’’,4’’ = 9.7Hz, 3J5’’,6’’a = 5.0Hz, 3J5’’,6’’b = 2.6Hz, 2H, H-
5’’, H-5’’’), 2.92 (sept, 3JH,H = 6.9Hz, 2H, 2*CH(CH3)2), 2.12, 2.09, 1.97, 1.86 (4s, 24H, 8*CH3COO),
3
13
1.28, 1.27 (2d, JH,H = 6.9Hz, 12H, 2*CH(CH3)(a,b)). C NMR (63 MHz, CDCl3): δ = 170.5, 169.7,
169.7, 169.5 (8*CH3COO), 166.9 (C-2, C-2’), 143.0 (C-5, C-5’), 140.5 (C-7a, C-7a’), 132.9 (C-3, C-
3’), 130.1 (C-6, C-6’), 127.4 (C-4, C-4’), 121.7 (C-3a, C-3a’), 113.0 (C-7, C-7’), 80.5 (C-1’’, C-1’’’),
75.5 (C-5’’, C-5’’’), 70.7 (C-3’’, C-3’’’), 69.9 (C-2’’, C-2’’’), 65.3 (C-4’’, C-4’’’), 62.3 (C-6’’, C-
6’’’), 34.0 (2*CH(CH3)2), 24.2, 24.1 (2*CH(CH3)(a,b)), 20.8, 20.8, 20.7, 20.5 (8*CH3COO).
Elemental analysis: calcd. for C50H58N2O20(1006.99): C, 59.64; H, 5.81; N, 2.78. Found: C, 59.08;
H, 5.54; N, 2.96. MS (EI, 70eV): m/z(%) = 1006 (41.02) [M]+; 676 (5); 499 (4); 394 (5); 331 (7); 169
(39); 109 (16). HRMS (ESI): calcd. for C50H59N2O20 [M+H]+ 1007.36557 and for C50H58N2NaO20
[M+Na]+ 1029.34751. Found 1007.36757 and 1029.3487.
1,1’-Di(2,3,4,6-tetra-O-acetyl-ß-D-mannopyranosyl)-5,5’-di(tert-butyl)isoindigo (5d). Starting
from the corresponding glycosyl isatine 4d (200 mg, 0.37 mmol) and P(NEt2)3 (102 mg, 0.41 mmol),
5d could be isolated after column chromatography as an orange brown brown solid (126 mg, 65%), mp
4
159-161°C; 1H NMR (300 MHz, CDCl3): δ = 9.13 (d, J4,6 = 1.9Hz, 2H, H-4, H-4’), 7.39 (d,
3
4
3J7,6 = 8.5Hz, 2H, H-7, H-7’), 7.32 (dd, J6,7 = 8.5Hz, J6,4 = 1.9Hz, 2H, H-6, H-6’), 6.01 (d,
3
3
3J1’’,2’’ = 1.4Hz, 2H, H-1’’, H-1’’’), 5.59 (dd, J2’’,1’’= 1.4Hz, J2’’,3’’ = 3.3Hz, 2H, H-2’’, H-2’’’), 5.41
3
3
(dd, J4’’,3’’ ≈ 3J4’’,5’’ ≈ 10.0Hz, 2H, H-4’’, H-4’’’), 5.33 (dd, J3’’,2’’ = 3.3Hz, 3J3’’,4’’ = 10.2Hz, 2H, H-

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3’’, H-3’’’), 4.30 (dd, J6’’a,6’’b = 12.4Hz, 3J6’’a,5’’ = 5.1Hz, 2H, H-6’’(a), H-6’’’(a)), 4.22 (dd,
3
3
2J6’’b,6’’a = 12.4Hz, 3J6’’b,5’’ = 2.4Hz, 2H, H-6’’(b), H-6’’’(b)), 3.89 (ddd, J5’’,4’’ = 9.9Hz, J5’’,6’’a
3
= 5.1Hz, J5’’,6’’b = 2.4Hz, 2H, H-5’’, H-5’’’), 2.11, 2.08, 1.97, 1.86 (4s, 24H, 8*CH3COO), 1.36 (s,
18H, 2*C(CH3)3). 13C NMR (75 MHz, CDCl3): δ = 170.5, 169.7, 169.7, 169.5 (8*CH3COO), 167.0 (C-
2, C-2’), 145.2 (C-5, C-5’), 140.0 (C-7a, C-7a’), 133.1 (C-3, C-3’), 128.9 (C-6, C-6’), 126.6 (C-4, C-
4’), 121.5 (C-3a, C-3a’), 112.6 (C-7, C-7’), 80.4 (C-1’’, C-1’’’), 75.5 (C-5’’, C-5’’’), 70.7 (C-3’’, C-
3’’’), 70.0 (C-2’’, C-2’’’), 65.4 (C-4’’, C-4’’’), 62.4 (C-6’’, C-6’’’), 34.8 (2*C(CH3)3), 31.5
(2*C(CH3)3), 20.8, 20.8, 20.7, 20.5 (8*CH3COO). MS (EI, 70 eV): m/z(%) =1034 (54) [M]+; 704 (6);
499 (4); 331 (7); 169 (55); 109 (26). HRMS (ESI): calcd. for C52H63N2O20 [M+H]+ 1035.39687 and for
C52H62N2NaO20 [M+Na]+ 1057.37881. Found 1035.39767 and 1057.3789.
1,1’-Di(2,3,4-tri-O-acetyl-ß-L-rhamnopyranosyl)isoindigo (5e). Starting from the corresponding
glycosyl isatine 4e (200 mg, 0.48 mmol) and P(NEt2)3 (129 mg, 0.52 mmol), 5e could be isolated after
column chromatography as an orange brown solid (130 mg, 68%), mp 130-132°C;
3
4
1H NMR (300 MHz, CDCl3): δ = 8.98 (dd, J4,5 = 8.2Hz, J4,6 = 1.3Hz, 2H, H-4, H-4’), 7.51 (dd,
4
3
3
4
3J7,6 = 8.2Hz, J7,5 = 1.2Hz, 2H, H-7, H-7’), 7.31 (ddd, J6,7 = 8.2Hz, J6,5 = 7.5Hz, J6,4 = 1.3Hz, 2H,
3
3
4
H-6, H-6’), 7.02 (ddd, J5,6 = 7.5Hz, J5,4 = 8.2Hz, J5,7 = 1.2Hz, 2H, H-5, H-5’), 5.97 (d,
3J1’’,2’’ = 1.5Hz, 2H, H-1’’, H-1’’’), 5.59 (dd, 3J2’’,1’’ = 1.5Hz, 3J2’’,3’’ = 3.1Hz, 2H, H-2’’, H-2’’’), 5.27-
5.16 (m, 4H, H-3’’, H-3’’’, H-4’’, H-4’’’), 3.79-3.69 (m, 2H, H-5’’, H-5’’’), 2.09, 1.96, 1.85 (3s, 18H,
6*CH3COO), 1.35 (d, 3J6’’,5’’ = 6.2Hz, 6H, 3*H-6’’, 3*H-6’’’). 13C NMR (63 MHz, CDCl3): δ = 170.0,
169.7, 169.6 (6*CH3COO), 166.7 (C-2, C-2’), 142.6 (C-7a, C-7a’), 132.8 (C-3, C-3’), 132.1 (C-6, C-
6’), 129.1 (C-4, C-4’), 122.4 (C-5, C-5’), 121.6 (C-3a, C-3a’), 113.2 (C-7, C-7’), 80.6 (C-1’’, C-1’’’),
74.1 (C-5’’, C-5’’’), 70.7 (C-3’’, C-3’’’), 70.2, 70.1 (C-2’’, C-2’’’, C-4’’, C-4’’’), 20.8, 20.8, 20.5
(6*CH3COO), 17.7 (C-6’’, C-6’’’). MS(EI, 70 eV): m/z (%) = 806 (61) [M]+; 534 (9); 273 (44); 213
(17); 171 (25); 153 (95); 111 (73). HRMS (ESI): calcd. for C40H43N2O16 [M+H]+ 807.26071 and for
C40H42N2NaO16 [M+Na]+ 829.24265. Found 807.26139 and 829.2443.
1,1’-Di(2,3,4-tri-O-acetyl-ß-L-rhamnopyranosyl)-5,5’-dimethylisoindigo (5f). Starting from the
corresponding glycosyl isatine 4f (400 mg, 0.92 mmol) and P(NEt2)3 (251 mg, 1.01mmol), 5f could be
isolated after column chromatography as an orange brown solid (343 mg, 89%), mp 242-244°C;
1H NMR (300 MHz, CDCl3): δ = 8.80 (d (br), 4J4,6 = 1.9Hz, 2H, H-4, H-4’), 7.38 (d, 3J7,6 = 8.2Hz, 2H,
3
H-7, H-7’), 7.11 (dd (br), 3J6,7 = 8.2Hz, 4J6,4 = 1.9Hz, 2H, H-6, H-6’), 5.96 (d, J1’’,2’’ = 1.6Hz, 2H, H-
3
1’’, H-1’’’), 5.58 (dd, J2’’,1’’ = 1.6Hz, 3J2’’,3’’ = 3.0Hz, 2H, H-2’’, H-2’’’), 5.28-5.17 (m, 4H, H-3’’, H-
3’’’, H-4’’, H-4’’’), 3.78-3.69 (m, 2H, H-5’’, H-5’’’), 2.34 (s (br), 6H, 2*CH3), 2.09, 1.96, 1.88 (3s,

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18H, 6*CH3COO), 1.34 (d, J6’’,5’’ = 6.2Hz, 6H, 3*H-6’’, 3*H-6’’’). 13C NMR (63 MHz, CDCl3): δ =
170.0, 169.8, 169.6 (6*CH3COO), 166.8 (C-2, C-2’), 140.3 (C-7a, C-7a’), 132.9 (C-3, C-3’), 132.7 (C-
6, C-6’), 131.7 (C-5, C-5’), 129.4 (C-4, C-4’), 121.8 (C-3a, C-3a’), 113.0 (C-7, C-7’), 80.4 (C-1’’, C-
1’’’), 74.1 (C-5’’, C-5’’’), 70.7 (C-3’’, C-3’’’), 70.3, 70.2 (C-2’’, C-2’’’, C-4’’, C-4’’’), 21.2, 20.9,
20.8, 20.6 (6*CH3COO, 2*CH3), 17.7 (C-6’’, C-6’’’). MS (EI, 70eV): m/z (%) = 834 (47) [M]+; 562
(17); 290 (26); 213 (10); 171 (17); 153 (83); 111 (59). HRMS (ESI): calcd. for C42H47N2O16 [M+H]+
835.29201 and for C42H46N2NaO16 [M+Na]+ 857.27395. Found 835.29147 and 857.27393.
1,1’-Di(2,3,4-tri-O-acetyl-ß-L-rhamnopyranosyl)-5,5’-diethylisoindigo (5g). Starting from the
corresponding glycosyl isatine 4g (400 mg, 0.89 mmol) and P(NEt2)3 (243 mg, 0.98 mmol), 5g could
be isolated after column chromatography as an orange brown solid (319 mg, 83%), mp 211-213°C;
4
3
1H NMR (300 MHz, CDCl3): δ = 8.83 (d, J4,6 = 1.8Hz, 2H, H-4, H-4’), 7.40 (d, J7,6 = 8.3Hz, 2H, H-
3
7, H-7’), 7.13 (dd, 3J6,7 = 8.3Hz, 4J6,4 = 1.9Hz, 2H, H-6, H-6’), 5.96 (d, J1’’,2’’ = 1.5Hz, 2H, H-1’’, H-
1’’’), 5.57 (dd, 3J2’’,1’’ = 1.5Hz, 3J2’’,3’’ = 3.0Hz, 2H, H-2’’, H-2’’’), 5.28-5.17 (m, 4H, H-3’’, H-3’’’, H-
4’’, H-4’’’), 3.79-3.69 (m, 2H, H-5’’, H-5’’’), 2.63 (q, 3JH,H = 7.5Hz, 4H, 2*CH2CH3), 2.08, 1.96, 1.86
3
3
(3s, 18H, 6*CH3COO), 1.34 (d, J6’’,5’’ = 6.2Hz, 6H, 3*H-6’’, 3*H-6’’’), 1.24 (t, JH,H = 7.5Hz, 6H,
2*CH2CH3). 13C NMR (63 MHz, CDCl3): δ = 170.0, 169.7, 169.6 (6*CH3COO), 166.9 (C-2, C-2’),
140.5 (C-7, C-7a’), 138.3 (C-5, C-5’), 132.9 (C-3, C-3’), 131.6 (C-6, C-6’), 128.4 (C-4, C-4’), 121.8
(C-3a, C-3a’), 113.0 (C-7, C-7’), 80.4 (C-1’’, C-1’’’), 74.0 (C-5’’, C-5’’’), 70.7 (C-3’’, C-3’’’), 70.3,
70.2 (C-2’’, C-2’’’, C-4’’, C-4’’’), 28.7 (2*CH2CH3), 20.8, 20.8, 20.5 (6*CH3COO), 17.7 (C-6’’, C-
6’’’), 16.0 (2*CH2CH3). Elemental analysis: calcd. for C44H50N2O16 (862.32): C, 61.25; H, 5.84; N,
3.25. Found: C, 61.07; H, 6.10; N, 3.13. MS (EI, 70 eV): m/z (%) = 862 (18) [M]+; 804 (5); 590 (10);
318 (26); 273 (32); 213 (12); 171 (25); 135 (91); 111 (83). HRMS (ESI): calcd. for C44H51N2O16
[M+H]+ 863.32331 and for C44H50N2NaO16 [M+Na]+ 885.30525. Found 863.32301 and 885.3054.
1,1’-Di(2,3,4-tri-O-acetyl-ß-L-rhamnopyranosyl)-5,5’-diisopropylisoindigo (5h). Starting from
the corresponding glycosyl isatine 4h (400 mg, 0.87 mmol) and P(NEt2)3 (237 mg, 0.96 mmol), 5h
could be isolated after column chromatography as an orange brown solid (309 mg, 80%), mp 147-
1
3
149°C; H NMR (250 MHz, CDCl3): δ = 8.89 (d, 4J4,6 = 1.9Hz, 2H, H-4, H-4’), 7.41 (d, J7,6 = 8.3Hz,
3
2H, H-7, H-7’), 7.17 (dd, 3J6,7 = 8.3Hz, 4J6,4 = 1.9Hz, 2H, H-6, H-6’), 5.97 (d, J1’’,2’’ = 1.5Hz, 2H, H-
1’’, H-1’’’), 5.57 (dd, 3J2’’,1’’ = 1.5Hz, 3J2’’,3’’ = 3.0Hz, 2H, H-2’’, H-2’’’), 5.30-5.16 (m, 4H, H-3’’, H-
3
3’’’, H-4’’, H-4’’’), 3.80-3.68 (m, 2H, H-5’’, H-5’’’), 2.91 (sept, JH,H = 6.9Hz, 2H, 2*CH(CH3)2),
3
2.08, 1.96, 1.86 (3s, 18H, 6*CH3COO), 1.34 (d, J6’’,5’’ = 6.2Hz, 6H, 3*H-6’’, 3*H-6’’’), 1.27, 1.26
3
(2d, JH,H = 6.9Hz, 12H, 2*CH(CH3)(a,b)). 13C NMR (75 MHz, CDCl3): δ = 170.0, 169.8, 169.6

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(6*CH3COO), 166.9 (C-2, C-2’), 142.9 (C-5, C-5’), 140.6 (C-7a, C-7a’), 133.0 (C-3, C-3’), 130.0 (C-
6, C-6’), 127.3 (C-4, C-4’), 121.7 (C-3a, C-3a’), 113.0 (C-7, C-7’), 80.4 (C-1’’, C-1’’’), 74.0 (C-5’’,
C-5’’’), 70.7 (C-3’’, C-3’’’), 70.3 , 70.2 (C-2’’, C-2’’’, C-4’’, C-4’’’), 34.0 (2*CH(CH3)2), 24.2
(2*CH(CH3)2), 20.9, 20.8, 20.6 (6*CH3COO), 17.7 (C-6’’, C-6’’’). MS (EI, 70 eV): m/z (%) = 890
(39.03) [M]+; 618 (9); 346 (19) ; 273 (14); 171 (13); 153 (54); 111(45). HRMS (ESI): calcd. for
C46H55N2O16 [M+H]+ 891.35461 and for C46H54N2NaO16 [M+Na]+ 913.33655. Found 891.35584 and
913.33800.
1,1’-Di(2,3,4-tri-O-acetyl-ß-L-rhamnopyranosyl)-5,5’-di(tert-butyl)isoindigo (5i). Starting from
the corresponding glycosyl isatine 4i (400 mg, 0.84 mmol) and P(NEt2)3 (229 mg, 0.93 mmol), 5i
could be isolated after column chromatography as an orange brown solid (301 mg, 78%), mp 181-
1
4
3
183°C; H NMR (250 MHz, CDCl3): δ = 9.11 (d, J4,6 = 2.0Hz, 2H, H-4, H-4’), 7.42 (d, J7,6 = 8.5Hz,
3
2H, H-7, H-7’), 7.33 (dd, 3J6,7 = 8.5Hz, 4J6,4 = 2.0Hz, 2H, H-6, H-6’), 5.98 (d, J1’’,2’’ = 1.5Hz, 2H, H-
3
1’’, H-1’’’), 5.57 (dd, J2’’,1’’ = 1.5Hz, J2’’,3’’ = 3.2Hz, 2H, H-2’’, H-2’’’), 5.29 (dd, J3’’,2’’ = 3.2Hz,
3
3
3
3
3J3’’,4’’ = 10.2Hz, 2H, H-3’’, H-3’’’), 5.20 (dd, J4’’,3’’ = 10.2Hz, J4’’,5’’ = 9.0Hz, 2H, H-4’’, H-4’’’),
3
3
3.76 (dq, J5’’,6’’ = 6.2Hz, J4’’,5’’ = 9.0Hz, 2H, H-5’’, H-5’’’), 2.09, 1.96, 1.86 (3s, 18H, 6*CH3COO),
1.35 (s, 18H, 2*C(CH3)3), 1.34 (d (overlayed), 6H, 3*H-6’’, 3*H-6’’’). 13C NMR (75 MHz,
CDCl3): δ = 170.0, 169.8, 169.5 (6*CH3COO), 167.1 (C-2, C-2’), 145.1 (C-5, C-5’), 140.1 (C-7a, C-
7a’), 133.1 (C-3, C-3’), 128.9 (C-6, C-6’), 126.5 (C-4, C-4’), 121.5 (C-3a, C-3a’), 112.6 (C-7, C-7’),
80.3 (C-1’’, C-1’’’), 73.9 (C-5’’, C-5’’’), 70.7 (C-3’’, C-3’’’), 70.3 , 70.3 (C-2’’, C-2’’’, C-4’’, C-4’’’),
34.7 (2*C(CH3)3), 31.5 (2*C(CH3)3), 20.8, 20.8, 20.5 (6*CH3COO), 17.7 (C-6’’, C-6’’’). MS (EI,
70eV): m/z (%) = 918 (100) [M]+, 646 (16), 374 (21), 273 (16), 213 (6), 171 (14), 153 (55), 111 (48).
HRMS (ESI): calcd. for C48H59N2O16 [M+H]+ 919.38591 and for C48H58N2NaO16 [M+Na]+ 941.36785.
Found 919.38584 and 941.3685.
General procedure for the deacetylation of N,N’-di-glycosylated isoindigos 6a-i: The N,N’-
diglycosylated isoindigo was dissolved in 0.1 M methanolic sodium methoxide solution (4 ml per 100
mg acetylated N,N’-diglycosylated isoindigo). After some time of stirring at 20 °C, most of the product
precipitated and was purified by filtration and subsequent washing with cold MeOH. Only compounds
6d and 6i were purified by column chromatography (ethyl acetate/ ethanol v:v = 10:1) after
neutralisation of the reaction mixture with acetic acid and following solvent removal under reduced
pressure.

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1,1’-Di-(ß-D-mannopyranosyl)isoindigo (6a). Starting from the corresponding acetylated derivative
5a (100 mg, 0.11 mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol), 6a could be isolated
as an orange brown solid (51 mg, 80%), mp 297-299°C; 1H NMR (300 MHz, DMSO-d6): δ = 8.88 (dd
3
(br), 3J4,5 = 8.2Hz, 4J4,6 = 1.2Hz, 2H, H-4, H-4’), 7.67 (d (br), J7,6 = 8.2Hz, 2H, H-7, H-7’), 7.31 (ddd,
3
4
3
3
3J6,7 = 8.2Hz, J6,5 = 7.5Hz, J6,4 = 1.2Hz, 2H, H-6, H-6’), 6.96 (ddd, J5,6 = 7.5Hz, J5,4 = 8.2Hz,
4J5,7 = 1.1Hz, 2H, H-5, H-5’), 5.63 (d, 3J1’’,2’’ = 1.1Hz, 2H, H-1’’, H-1’’’), 5.12 (d, 3JOH,H = 4.8Hz, 2H,
3
3
2*OH), 4.93 (d, JOH,H = 4.4Hz, 2H, 2*OH), 4.87 (d, JOH,H = 4.8Hz, 2H, 2*OH), 4.57 (t,
3JOH,H = 5.5Hz, 2H, 2*OH), 3.86-3.75 (m, 4H, H-2’’, H-2’’’, H-6’’(a), H-6’’’(a)), 3.60-3.49 (m, 6H,
H-3’’, H-3’’’, H-4’’, H-4’’’, H-6’’(b), H-6’’’(b)), 3.34-3.28 (m, 2H, H-5’’, H-5’’’). 13C NMR (63
MHz, DMSO-d6): δ = 166.4 (C-2, C-2’), 144.4, 132.8 (2*C, 2*C’), 132.3 (C-6, C-6’), 128.0 (C-4, C-
4’), 121.3 (C-5, C-5’), 120.8 (C, C’), 115.6 (C-7, C-7’), 82.7 (C-1’’, C-1’’’), 81.1 (C-5’’, C-5’’’), 73.5,
66.5 (C-3’’, C-3’’’, C-4’’, C-4’’’), 71.8 (C-2’’, C-2’’’), 61.4 (C-6’’, C-6’’’). Elemental analysis: calcd.
for C28H30N2O12 (586.54): C, 57.34, H, 5.16, N, 4.78. Found: C, 57.33, H, 5.46, N, 4.95. HRMS (ESI):
calcd. for C28H31N2O12 [M+H]+ 587.18715 and for C28H30N2NaO12 [M+Na]+ 609.16910. Found
587.18783 and 609.17029.
1,1’-Di-(ß-D-mannopyranosyl)-5,5’-dimethylisoindigo (6b). Starting from the corresponding
acetylated derivative 5b (100 mg, 0.11mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol),
6b could be isolated as an orange brown solid (50 mg, 77%), mp 257-259°C;
4
3
1H NMR (300 MHz, DMSO-d6): δ = 8.73 (d, J4,6 = 1.4Hz, 2H, H-4, H-4’), 7.55 (d, J7,6 = 8.3Hz, 2H,
3
H-7, H-7’), 7.12 (dd, 3J6,7 = 8.3Hz, 4J6,4 = 1.4Hz, 2H, H-6, H-6’), 5.62 (d, J1’’,2’’ = 1.1Hz, 2H, H-1’’,
H-1’’’), 5.09 (d, 3JOH,H = 4.4Hz, 2H, 2*OH), 4.94, 4.88 (2*br, 4H, 4*OH), 4.56 (t, 3JOH,H = 5.5Hz, 2H,
2*OH), 3.85-3.74 (m, 4H, H-2’’, H-2’’’, H-6’’(a), H-6’’’(a)), 3.59-3.47 (m, 6H, H-3’’, H-3’’’, H-4’’,
H-4’’’, H-6’’(b), H-6’’’(b)), 3.34-3.27 (m, 2H, H-5’’, H-5’’’), 2.26 (s, 6H, 2*CH3). 13C NMR (63
MHz, DMSO-d6): δ = 166.5 (C-2, C-2’), 142.2, 132.9 (2*C, 2*C’), 132.8 (C-6, C-6’), 129.8 (C, C’),
128.1 (C-4, C-4’), 120.9 (C, C’), 115.4 (C-7, C-7’), 82.6 (C-1’’, C-1’’’), 81.0 (C-5’’, C-5’’’), 73.5,
66.5 (C-3’’, C-3’’’, C-4’’, C-4’’’), 71.9 (C-2’’, C-2’’’), 61.4 (C-6’’, C-6’’’), 21.0 (2*CH3). Elemental
analysis: calcd. for C30H34N2O12 (614.60): C, 58.63, H, 5.58, N, 4.56. Found: C, 58.17, H, 5.18,
N, 4.32. HRMS (ESI): calcd. for C30H35N2O12 [M+H]+ 615.21845 and for C30H34N2NaO12 [M+Na]+
637.2004. Found 615.21784 and 637.1999.
5,5’-Diisopropyl-1,1’-di(ß-D-mannopyranosyl)isoindigo (6c). Starting from the corresponding
acetylated derivative 5c (100 mg, 0.10 mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol),
6c could be isolated as an orange brown solid (43 mg, 65%), mp 287-289°C;

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3
1H NMR (300 MHz, DMSO-d6): δ = 8.80 (d, J4,6 = 1.9Hz, 2H, H-4, H-4’), 7.58 (d, J7,6 = 8.4Hz, 2H,
3
H-7, H-7’), 7.19 (dd, 3J6,7 = 8.4Hz, 4J6,4 = 1.9Hz, 2H, H-6, H-6’), 5.63 (d, J1’’,2’’ = 1.1Hz, 2H, H-1’’,
3
H-1’’’), 5.10 (d, JOH,H = 4.9Hz, 2H, 2*OH), 4.91 (d, JOH,H = 4.9Hz, 2H, 2*OH), 4.84 (d,
3
3
3JOH,H = 5.5Hz, 2H, 2*OH), 4.56 (t, JOH,H = 5.6Hz, 2H, 2*OH), 3.85-3.74 (m, 4H, H-2’’, H-2’’’, H-
6’’(a), H-6’’’(a)), 3.59-3.48 (m, 6H, H-3’’, H-3’’’, H-4’’, H-4’’’, H-6’’(b), H-6’’’(b)), 3.36-3.29 (m,
3
3
2H, H-5’’, H-5’’’), 2.83 (sept, JH,H = 6.9Hz, 2H, 2*CH(CH3)2), 1.22, 1.21 (2*d, JH,H = 6.9Hz, 12H,
2*CH(CH3)(a,b)). 13C NMR (63 MHz, DMSO-d6): δ = 166.6 (C-2, C-2’), 142.4, 141.2, 133.0 (3*C,
3*C’), 130.2 (C-6, C-6’), 125.9 (C-4, C-4’), 120.9 (C, C’), 115.4 (C-7, C-7’), 82.5 (C-1’’, C-1’’’), 80.9
(C-5’’, C-5’’’), 73.4, 66.5 (C-3’’, C-3’’’, C-4’’, C-4’’’), 71.9 (C-2’’, C-2’’’), 61.5 (C-6’’, C-6’’’), 33.5
(2*CH(CH3)2), 24.3, 24.3 (2*CH(CH3)(a,b)). Elemental analysis: calcd. for C34H42N2O12 (670.70): C,
60.89, H, 6.31, N, 4.18. Found: C, 60.76, H, 6.42, N, 4.44. HRMS (ESI): calcd. for C34H43N2O12
[M+H]+ 671.28105 and for C34H42N2NaO12 [M+Na]+ 693.26300. Found 671.28258 and 693.26447.
5,5’-Di(tert-butyl)-1,1’-di(ß-D-mannopyranosyl)isoindigo (6d). Starting from the corresponding
acetylated derivative 5d (100 mg, 0.10 mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol),
6d could be isolated after column chromatography (ethyl acetate/ ethanol) as an orange brown solid
(34 mg, 50%), mp 225-227°C; 1H NMR (300 MHz, DMSO-d6): δ = 9.00 (d, 4J4,6 = 1.9Hz, 2H, H-4, H-
4’), 7.58 (d, 3J7,6 = 8.6Hz, 2H, H-7, H-7’), 7.35 (dd, 3J6,7 = 8.6Hz, 4J6,4 = 1.9Hz, 2H, H-6, H-6’), 5.63 (s
(br), 2H, H-1’’, H-1’’’), 5.23-4.92 (m, 3H, 6H, 6*OH), 4.70-4.52 (m, 2H, 2*OH), 3.86-3.74 (m, 4H,
H-2’’, H-2’’’, H-6’’(a), H-6’’’(a)), 3.61-3.45 (m, 6H, H-3’’, H-3’’’, H-4’’, H-4’’’, H-6’’(b), H-6’’’(b)),
3.40-3.30 (m, 2H, H-5’’, H-5’’’), 1.30 (s, 18H, 2*C(CH3)3). 13C NMR (63 MHz, DMSO-d6): δ = 166.7
(C-2, C-2’), 143.4, 142.0, 133.2 (3*C, 3*C’), 129.2 (C-6, C-6’), 124.9 (C-4, C-4’), 120.6 (C, C’),
115.1 (C-7, C-7’), 82.5 (C-1’’, C-1’’’), 80.8 (C-5’’, C-5’’’), 73.4, 66.5 (C-3’’, C-3’’’, C-4’’, C-4’’’),
71.9 (C-2’’, C-2’’’), 61.5 (C-6’’, C-6’’’), 34.5 (2*C(CH3)3), 31.5 (2*C(CH3)3). HRMS (ESI): calcd. for
C36H47N2O12 [M+ H]+ 699.31235 and for C36H46N2NaO12 [M+Na]+ 721.29430. Found 699.31381 und
721.29635.
1,1’-Di-(ß-L-rhamnopyranosyl)isoindigo (6e). Starting from the corresponding acetylated
derivative 5d (100 mg, 0.12 mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol), 6d could
1
be isolated as an orange brown solid (58 mg, 84%), mp 274-275°C; H NMR (300 MHz, DMSO-
3
4
d6): δ = 8.88 (dd (br), 3J4,5 = 8.2Hz, 4J4,6 = 1.3Hz, 2H, H-4, H-4’), 7.62 (dd (br), J7,6 = 8.2Hz, J7,5
=
1.2Hz, 2H, H-7, H-7’), 7.31 (ddd, 3J6,7 = 8.2Hz, 3J6,5 = 7.5Hz, 4J6,4 = 1.3Hz, 2H, H-6, H-6’), 6.95 (ddd,
4
3J5,6 = 7.5Hz, 3J5,4 = 8.2Hz, J5,7 = 1.2Hz, 2H, H-5, H-5’), 5.62 (d, 3J1’’,2’’ = 1.3Hz, 2H, H-1’’, H-1’’’),
3
3
3
5.14 (d, JOH,H = 4.9Hz, 2H, 2*OH), 4.99 (d, JOH,H = 4.9Hz, 2H, 2*OH), 4.87 (d, JOH,H = 5.7Hz, 2H,

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3
2*OH), 3.85 (ddd, J2’’,1’’ = 1.3Hz, J2’’,3’’ = 3.3Hz, J2’’,OH = 4.9Hz, 2H, H-2’’, H-2’’’), 3.52-3.45 (m,
3
3
3
2H, H-3’’, H-3’’’), 3.43-3.32 (m, 4H, H-4’’, H-4’’’, H-5’’, H-5’’’), 1.28 (d, J6’’,5’’ = 5.5Hz, 6H, 3*H-
6’’, 3*H-6’’’). 13C NMR (63MHz, DMSO-d6): δ = 166.4 (C-2, C-2’), 144.3, 132.7 (2*C, 2*C’), 132.7
(C-6, C-6’), 128.1 (C-4, C-4’), 121.3 (C-5, C-5’), 120.9 (C, C’), 115.2 (C-7, C-7’), 82.7 (C-1’’, C-1’’),
75.6, 71.5 (C-4’’, C-4’’’, C-5’’, C-5’’’), 73.2 (C-3’’, C-3’’’), 72.0 (C-2’’, C-2’’’), 18.3 (C-6’’, C-6’’’).
HRMS (ESI): calcd. for C28H31N2O10 [M+H]+ 555.19732 and for C28H30N2NaO10 [M+Na]+ 577.17927.
Found 555.19807 and 577.18003.
5,5’-Dimethyl-1,1’-di(ß-L-rhamnopyranosyl)isoindigo (6f). Starting from the corresponding
acetylated derivative 5f (100 mg, 0.12 mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol),
6f could be isolated as an orange brown solid (50 mg, 72%), mp 285-287°C;
4
3
1H NMR (300 MHz, DMSO-d6): δ = 8.72 (d (br), J4,6 = 1.9Hz, 2H, H-4, H-4’), 7.49 (d, J7,6 = 8.3Hz,
3
2H, H-7, H-7’), 7.12 (dd (br), J6,7 = 8.3Hz, 4J6,4 = 1.9Hz, 2H, H-6, H-6’), 5.62 (d, 3J1’’,2’’ = 1.3Hz, 2H,
H-1’’, H-1’’’), 5.09 (d, 3JOH,H = 4.9Hz, 2H, 2*OH), 4.97 (d, 3JOH,H = 4.9Hz, 2H, 2*OH), 4.84 (d, 3JOH,H
3
3
3
= 5.8Hz, 2H, 2*OH), 3.83 (ddd, J2’’,1’’ = 1.3Hz, J2’’,3’’ = 3.3Hz, J2’’,OH = 4.9Hz, 2H, H-2’’, H-2’’’),
3.53-3.46 (m, 2H, H-3’’, H-3’’’), 3.42-3.32 (m, 4H, H-4’’, H-4’’’, H-5’’, H-5’’’) 2.25 (s (br), 6H,
3
2*CH3)), 1.27 (d, J6’’,5’’ = 5.6Hz, 6H, 3*H-6’’, 3*H-6’’’). 13C NMR (63 MHz, DMSO-d6): δ = 166.5
(C-2, C-2’), 142.2, 132.8 (2*C, 2*C’), 132.7 (C-6, C-6’), 129.8 (C, C’), 128.2 (C-4, C-4’), 120.9 (C,
C’), 114.9 (C-7, C-7’), 82.5 (C-1’’, C-1’’), 75.5, 71.6 (C-4’’, C-4’’’, C-5’’, C-5’’’), 73.2 (C-3’’, C-
3’’’), 72.0 (C-2’’, C-2’’’), 21.0 (2*CH3), 18.3 (C-6’’, C-6’’’). Elemental analysis: calcd. for
C30H34N2O10 (582.60): C, 61.85; H, 5.88; N, 4.81. Found: C, 62.02, H, 5.42, N, 4.65.
5,5’-Diethyl-1,1’-di(ß-L-rhamnopyranosyl)isoindigo (6g). Starting from the corresponding
acetylated derivative 5g (100 mg, 0.12 mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol),
6g could be isolated as an orange brown solid (57 mg, 81%), mp 306-308°C;
4
3
1H NMR (300 MHz, DMSO-d6): δ = 8.75 (d, J4,6 = 1.7Hz, 2H, H-4, H-4’), 7.52 (d, J7,6 = 8.3Hz, 2H,
3
H-7, H-7’), 7.16 (dd, J6,7 = 8.3Hz, J6,4 = 1.7Hz, 2H, H-6, H-6’), 5.63 (d, J1’’,2’’ = 1.0Hz, 2H, H-1’’,
4
3
H-1’’’), 5.11, 4.98, 4.85 (3*br, 6H, 6*OH), 3.84 (br, 2H, H-2’’, H-2’’’), 3.53-3.48 (m (br), 2H, H-3’’,
3
H-3’’’), 3.42-3.31 (m, 4H, H-4’’, H-4’’’, H-5’’, H-5’’’), 2.54 (q, JH,H = 7.5Hz, 4H, 2*CH2CH3), 1.27
3
3
(d, J6’’,5’’ = 5.2Hz, 6H, 3*H-6’’, 3*H-6’’’), 1.18 (t, JH,H = 7.5Hz, 6H, 2*CH2CH3). 13C NMR (63
MHz, DMSO-d6): δ = 166.5 (C-2, C-2’), 142.3, 136.5, 132.9 (3*C, 3*C’), 131.7 (C-6, C-6’), 127.3 (C-
4, C-4’), 121.0 (C, C’), 115.0 (C-7, C-7’), 82.5 (C-1’’, C-1’’), 75.5, 71.6 (C-4’’, C-4’’’, C-5’’, C-5’’’),
73.2 (C-3’’, C-3’’’), 72.0 (C-2’’, C-2’’’), 28.3 (2*CH2CH3), 18.3 (C-6’’, C-6’’’), 16.4 (2*CH2CH3).
Elemental analysis: calcd. for C32H38N2O10 (610.65): C, 62.94; H, 6.27; N, 4.59. Found: C, 62.86;

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H, 5.99; N, 5.07. HRMS (ESI): calcd. for C32H39N2O10 [M+H]+ 611.25992 and for C32H38N2NaO10
[M+Na]+ 633.24187. Found 611.25920 and 633.24153.
5,5’-Diisopropyl-1,1’-di(ß-L-rhamnopyranosyl)isoindigo (6h). Starting from the corresponding
acetylated derivative 5h (100 mg, 0.11 mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol),
6h could be isolated as an orange brown solid (56 mg, 78%), mp 299-301°C;
4
3
1H NMR (300 MHz, DMSO-d6): δ = 8.80 (d, J4,6 = 1.8Hz, 2H, H-4, H-4’), 7.52 (d, J7,6 = 8.4Hz, 2H,
3
H-7, H-7’), 7.19 (dd, 3J6,7 = 8.4Hz, 4J6,4 = 1.8Hz, 2H, H-6, H-6’), 5.63 (d, J1’’,2’’ = 1.1Hz, 2H, H-1’’,
H-1’’’), 5.11, 4.97, 4.85 (3*br, 6H, 6*OH), 3.84 (br, 2H, H-2’’, H-2’’’), 3.54-3.48 (m (br), 2H, H-3’’,
3
H-3’’’), 3.43-3.31 (m, 4H, H-4’’, H-4’’’, H-5’’, H-5’’’), 2.82 (sept, JH,H = 6.8Hz, 2H, 2*CH(CH3)2),
3
3
1.27 (d, J6’’,5’’ = 5.3Hz, 6H, 3*H-6’’, 3*H-6’’’), 1.21, 1.20 (2*d, JH,H = 6.8Hz, 12H,
2*CH(CH3)(a,b)). 13C NMR (63 MHz, DMSO-d6): δ = 166.5 (C-2, C-2’), 142.4, 141.2, 133.0 (3*C,
3*C’), 130.2 (C-6, C-6’), 126.0 (C-4, C-4’), 120.9 (C, C’), 115.0 (C-7, C-7’), 82.5 (C-1’’, C-1’’), 75.4,
71.5 (C-4’’, C-4’’’, C-5’’, C-5’’’), 73.1 (C-3’’, C-3’’’), 72.0 (C-2’’, C-2’’’), 33.5 (2*CH(CH3)2), 24.3
(2*CH(CH3)2), 18.3 (C-6’’, C-6’’’). HRMS (ESI): calcd. for C34H43N2O10 [M+H]+ 639.29122 and for
C34H42N2NaO10 [M+Na]+ 661.27317. Found 639.29195 and 661.27431.
5,5’-Di(tert-butyl)-1,1’-di(ß-L-rhamnopyranosyl)isoindigo (6i). Starting from the corresponding
acetylated derivative 5i (100 mg, 0.11 mmol) and 0.1 M sodium methoxide solution (4 ml, 0.4 mmol),
6i could be isolated after column chromatography (ethyl acetate/ ethanol) as an orange brown solid (36
mg, 50%), mp 249-251°C; 1H NMR (300 MHz, DMSO-d6): δ = 8.99 (d, 4J4,6 = 2.0Hz, 2H, H-4, H-4’),
3
3
4
7.52 (d, J7,6 = 8.6Hz, 2H, H-7, H-7’), 7.35 (dd, J6,7 = 8.6Hz, J6,4 = 2.0Hz, 2H, H-6, H-6’), 5.62 (s
(br), 2H, H-1’’, H-1’’’), 5.11 (d, 3JOH,H = 4.9Hz, 2H, 2*OH), 4.96 (d, 3JOH,H = 4.9Hz, 2H, 2*OH), 4.83
(d, 3JOH,H = 5.8Hz, 2H, 2*OH), 3.83 (m (br), 2H, H-2’’, H-2’’’), 3.55-3.48 (m (br), 2H, H-3’’, H-3’’’),
3.44-3.31 (m, 4H, H-4’’, H-4’’’, H-5’’, H-5’’’), 1.29 (s, 18H, 2*C(CH3)3).
13C NMR (75 MHz, DMSO-d6): δ = 166.7 (C-2, C-2’), 143.4, 141.9, 133.1 (3*C, 3*C’), 129.2 (C-6,
C-6’), 125.1 (C-4, C-4’), 120.7 (C, C’), 114.6 (C-7, C-7’), 82.5 (C-1’’, C-1’’), 75.3, 71.5 (C-4’’, C-
4’’’, C-5’’, C-5’’’), 73.1 (C-3’’, C-3’’’), 72.0 (C-2’’, C-2’’’), 34.5 (2*C(CH3)3), 31.5 (2*C(CH3)3),
18.3 (C-6’’, C-6’’’). HRMS (ESI): calcd. for C36H47N2O10 [M+H]+ 667.32252 and for C36H46N2NaO10
[M+Na]+ 689.30447. Found 667.32223 and 689.30401.
Acknowledgment

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Financial support by the DFG (grant no. LA 1301/9-1), by the DAAD and by the State of Syria
(scholarship for B. S.) is gratefully acknowledged.
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Synthesis of N,N’-Diglycosylated Isoindigos
Dennis Kleeblatt, Baraa Siyo, Martin Hein, Viktor Iaroshenko, Jamshed Iqbal, Alexander Villinger, Peter
Langer*

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O
OH
O
N
O
OAc
HO
OH
O
OAc
HO
OH
OH
AcO
OAc
O
HO
N
O
HO
HO
OH
OH
O
N
OH
O
HO