Reactivity tournament of isothiocyanato-functionalized saccharides with 1,6-diamino-3,6-oxaoctane

Article abstract of DOI:10.1007/s007060200022

Thiourea-bridged glycoclusters and glycodendrimers are described in the literature as mimetics of (oligoantennary) oligosaccharides to serve as high-affinity lectin ligands. In extension of this concept, the assembly of different, structurally varied isot

Full text of DOI:10.1007/s007060200022

Monatshefte fuÈr Chemie 133, 473±483 ꢀ2002)
Reactivity Tournament
of Isothiocyanato-Functionalized
Saccharides with 1,6-Diamino-3,6-oxaoctane
Ã
Mark Walter and Thisbe K. Lindhorst
Christiana Albertina University of Kiel, Institute of Organic Chemistry, D-24098 Kiel, Germany
Summary. Thiourea-bridged glycoclusters and glycodendrimers are described in the literature as
mimetics of ꢀoligoantennary) oligosaccharides to serve as high-af®nity lectin ligands. In extension
of this concept, the assembly of different, structurally varied isothiocyanato-functionalized sugar
derivatives on an oligoamine scaffold would lead to novel mixed glycoclusters. To control this
approach, the relative reactivities of the isothiocyanates used in the thiourea-bridging reaction have
to be known. Therefore, competition experiments with six different sugar isothiocyanates were
carried out using 1,8-diamino-3,6-dioxaoctane as a symmetrical difunctionalized core molecule.
1
Reactivities were ranked on the basis of integration ratios in the H NMR spectra. A ®rst mixed
thiourea-bridged glycocluster was successfully prepared.
Keywords. Sugar isothiocyanates; Thiourea bridging; Carbohydrates; Bioorganic chemistry.
Introduction
The oligosaccharide portions found in glycoproteins and glycolipids have
important functions in cell biology [1]. Due to their structural diversity they can
serve to store biological information, e.g. in cell-cell recognition and adhesion
processes, or to assist the control of biochemical events [2, 3]. Molecular
recognition of carbohydrate ligands is mediated by specialized proteins called
lectins and selectins [4]. Lectins may contain one or more carbohydrate recognition
domains ꢀCRDs) on a single peptide or protein chain, respectively, or they may
occur as clusters, e.g. on cell surfaces [5]. Multivalent binding of the receptor
protein CRDs to multiple copies of carbohydrate ligands as presented in
oligoantennary glycoconjugates can lead to high avidities, a ®nding which has
been named the cluster effect [6, 7]. Because multivalency has been recognized as
an important characteristic of carbohydrate-protein interactions [8±10], numerous
synthetic multivalent neoglycoconjugates of different architecture have been
introduced [11±13], for example to prevent early adhesion of neutrophiles to
endothelial surfaces [14] or to block microbial adhesion [15, 16].
Ã
Corresponding author. E-mail: tklind@oc.uni-kiel.de

474
M. Walter and T. K. Lindhorst
Representative classes of mimetics of oligosaccharides and oligoantennary
glycoconjugates have been called glycoclusters and glycodendrimers [17±19]. A
feasible approach for their synthesis includes a coupling reaction between an
oligovalent core molecule and a sugar derivative. As glycosylation reactions suffer
from the fact that they have to be optimized for every individual case, alternative
approaches have been sought to link a carbohydrate derivative to a scaffold
molecule, among which the thiourea-bridging strategy has become a very suc-
cessful one [20±23]. This method combines an isothiocyanato-functionalized
carbohydrate derivative [24] with a branched or dendritic oligoamine. Accordingly,
thiourea-bridged glycodendrimers and glycoclusters have been prepared with
glycosyl isothiocyanates and p-NCS-phenyl glycosides, and 6-deoxy-6-isothio-
cyanato-functionalized saccharides have been employed for the synthesis of
thiourea-bridged glycoclusters [25, 26]. Usually, such reactions proceed with high
yields and do not require tedious optimization of reaction conditions.
One of our projects involves the clustering of structurally different NCS-
functionalized sugar derivatives to develop high-af®nity ligands for various lectins.
Using derivatives with different NCS-functionalized spacers would allow to vary
the resulting glycoclusters with respect to their conformational ¯exibility. Fur-
thermore, combination of different carbohydrate ligands in one thiourea-bridging
reaction can eventually lead to highly diversi®ed glycoclusters of a mixed type.
To allow for a rational synthesis of mixed glycoclusters of this kind in
one pot, a grading of the reactivities of the reaction partners is necessary [27].
This paper describes a reactivity tournament of sugar isothiocyanates of different
structural characteristics to obtain their relative reactivities in thiourea-bridging
reactions.
Results and Discussion
Six different sugar isothiocyanates ꢀ1±6, Fig. 1) were chosen for comparison of
their reactivities in thiourea-bridging: glycosyl isothiocyanates 1 and 2, alkyl
isothiocyanates 3 and 4, and aryl isothiocyanates 5 and 6. As we are especially
interested in the inhibition of mannose-speci®c bacterial adhesion [28], mannose
was chosen as starting material for all derivatives except for 1 which was included
to obtain a hint about unexpected reactivity differences of analogous derivatives of
different sugar series. Compounds 1 [29], 2 [29], 3 [30], 4 [25], and 6 [22] were
synthesized according to standard procedures. A new route was followed for the
preparation of 5, involving direct glycosylation of 4-isothiocyanatobenzylalcohol
instead of glycosylation of 4-nitrobenzylalcohol and subsequent derivatization of
the p-nitro group. This method allowed to exclude the possibility of O ! N-acetyl
migration.
For the design of the competition experiments it has to be taken into account
that in the thiourea-bridging reaction of sugar isothiocyanates with oligoamines
the reactivity of the second amino group is in¯uenced by reaction of the ®rst
one. Therefore, a diamine instead of a monoamine was chosen for the reactivity
tournament to be closer to the real case scenario of the preparation of thiourea-
bridged glycoclusters and glycodendrimers. The reaction between two different
sugar isothiocyanates ꢀX and Y, Fig. 2) and a diamine can lead to three products:

Reactivity of Functionalized Saccharides
475
Fig. 1. Sugar isothiocyanates 1±6
two homodimers and one heterodimer ꢀFig. 2). The diamine used in the reaction
has to be soluble in an inert solvent. Because our ®rst choice, 1,6-diaminohexane,
had to be dissolved in protic solvents such as ethanol, 1,8-diamino-3,6-dioxaoctane
was chosen instead. It is a symmetrical difunctionalized core molecule soluble in
dichloromethane.
First, all homodimers ꢀ1a±6a) were prepared by thiourea-bridging with the
above diamine ꢀFig. 3), mainly to be used as standards in NMR analysis ꢀTable 1).
Then, for each competition experiment a pair of sugar isothiocyanates chosen from
compounds 1±6 ꢀFig. 1) was selected. Two equivalents of each relative to the
diamine core molecule were dissolved in boiling dichloromethane, and the diamine
was added dropwise as a solution in dichloromethane. The reaction mixture was
stirred under re¯ux for three hours; then the solvent was removed under reduced
pressure. Flash chromatography or HPLC did not allow the complete separation
of the three different reaction products. Therefore, it was decided to use ¯ash
chromatography to separate the excess of educts from the product mixture. The two
fractions thus obtained were analyzed by NMR spectroscopy, and the NMR spectra
were used to estimate the relative reactivities of the isothiocyanates employed.

476
M. Walter and T. K. Lindhorst
Fig. 2. The competition experiment: reaction of two different sugar isothiocyanates in the thiourea-
bridging reaction
Fig. 3. Thiourea-bridging reaction to obtain the homodimers 1a±6a

Reactivity of Functionalized Saccharides
477
Table 1. 1H NMR shifts of H-1 signals of the employed sugar isothiocyanates and their respective
dimers
ꢀꢀ1H)=ppm
B0=MHz,
solvent
ꢀꢀ1H)=ppm
B0=MHz,
solvent
1
2
3
4
5
6
4.99
5.53
4.86
4.72
4.83
5.47
400, CDCl3
400, CDCl3
400, CDCl3
400, CDCl3
400, CDCl3
400, CDCl3
1a
2a
3a
4a
5a
6a
5.87
5.99
4.88
4.65
4.88
5.52
500, acetone-d6
500, acetone-d6
400, CDCl3
400, CDCl3
500, CDCl3
500, CDCl3
The ratio of unreacted starting materials ꢀeducts X and Y) as well as the ratio of
glycosyl moieties X and Y present in the dimer mixtures could be obtained from
the 1H NMR spectra of the respective fractions. Two redundant informations were
extracted from the spectra in each case: From the spectrum of the excess educts,
the turnover of each educt isothiocyanate could be estimated, and from the
spectrum of the product mixture it could be deduced which derivative had reacted
with the amine to which extent. As in most cases the sugar H-1 signals were well
separated from the other resonances, the integration of these peaks ꢀTable 1)
formed the basis for the determination of relative reactivities. The integration of the
relevant signals of the NMR spectra of both fractions provided the same infor-
mation for an individual competition experiment as exempli®ed for the competition
reaction between 4 and 5 ꢀCꢀ4=5) in Table 2; Fig. 4).
The competition experiments clearly showed tremendous differences in the
reactivity of different isothiocyanato-functionalized sugars when examined in the
thiourea-bridging reaction ꢀTable 2). The glycosyl isothiocyanates 1 and 2 were by
far the most reactive derivatives due to the special reactivity of the anomeric
Table 2. Results of the reactivity tournament employing competition experiments between two
different sugar isothiocyanates X and Y
CꢀX=Y)1
Educts
Products
Major product
Turnover=
% X
Turnover=
% Y
% X in dimer
mixture
% Y in dimer
mixture
Cꢀ1=2)
Cꢀ1=5)
Cꢀ2=3)
Cꢀ2=4)
Cꢀ2=5)
Cꢀ2=6)
Cꢀ3=4)
Cꢀ3=5)
Cꢀ4=5)
Cꢀ5=6)
44
83
94
97
91
88
37
14
16
54
56
17
6
49
51
20
ꢁ 1
1
2
1
2
2
2
2
4
5
5
5
80
ꢀ 99
99
3
9
86
2
±
14
2
±
12
63
86
84
46
38
2
±
62
2
±
18
56
82
44
1
Competition reaction of sugar isothiocyanates X and Y; 2 Percentage in dimer mixture could not be
1
determined because of overlapping signals in the H NMR spectrum

478
M. Walter and T. K. Lindhorst
Fig. 4. ꢀa) 1H NMR signals of the H-1 protons of excess educts obtained in the competition
experiment between 4 and 5; ꢀb) 1H NMR signals of the H-1 protons of the product mixture obtained
in the competition experiment between 4 and 5; the signals were often broad, especially in the cases
of 1a and 2a where acetone-d6 was used as solvent for better resolved signals
position. Signi®cant differences of the reactivities of the ꢁ-mannosyl ꢀ2) and ꢂ-
glucosyl isothiocyanate ꢀ1) were not found. The derivatives with an aromatic
aglycone formed a second group with similar reactivity. In this case, the mesomeric
effect provided by the phenyl moiety may decrease the electrophilicity of the NCS-
carbon. It could be shown that the p-NCS-benzyl glycoside 5 was slightly more
reactive than the p-NCS-phenyl mannoside 6. An explanation for this difference
might be given on the basis of competing mesomeric effects. Among the alkyl
isothiocyanates, the 6-NCS-modi®ed derivative 4 is clearly more reactive than 3
which carries the NCS-group on the aliphatic spacer aglycone.
From integration of the broad H-1 signals in the measured 1H NMR spectra the
relative reactivities of the sugar isothiocyanates tested could be unequivocally
deduced, leading to an order of reactivity of 2 ꢀ 1 ꢂ 5 > 6 ꢂ 4 > 3.
Based on this ranking, a ®rst rational synthesis of a mixed thiourea-bridged
glycocluster was carried out. Tris-ꢀ2-aminoethyl)-amine was selected as branched

Reactivity of Functionalized Saccharides
479
Fig. 5. Preparation of the de®ned mixed glycocluster [ꢀ2)1ꢀ3)2] ꢀ7)
triamine to be reacted with the most reactive isothiocyanate 2 and the least reactive
derivative 3 in one pot ꢀFig. 5). A molecule of the composition [ꢀ2)1ꢀ3)2] ꢀ7) was
selected as the target glycocluster. As 2 was shown to be 16 times more reactive
than 3, one equivalent of 2 and 32 equivalents of 3 were therefore reacted with one
equivalent of the core molecule. The obtained product mixture was analyzed by
MALDI-TOF mass spectrometry, revealing three different mass peaks at
m=z ˆ 1401.44 ꢀcorresponding to [ꢀ2)2ꢀ3)1]), m=z ˆ 1489.49 ꢀcorresponding to
the desired cluster [ꢀ2)1ꢀ3)2]), and m=z ˆ 1577.54 ꢀcorresponding to ꢀ3)3). The
mass peak for the target cluster was clearly predominating over the others. Even
though integration of MALDI-TOF peaks cannot necessarily form the basis of a

480
M. Walter and T. K. Lindhorst
quantitative analysis, there is not doubt that the target glycocluster 7 was formed as
the main product in this experiment.
In conclusion, we have determined the relative reactivities of six structurally
different sugar isothiocyanates in a thiourea-bridging reaction using an aliphatic
diamine as the core molecule. The determined reactivities can form the basis of a
controlled synthesis of mixed glycoclusters as shown on the example of 7.
Experimental
Melting points were determined in capillary tubes in an Apotec apparatus and are uncorrected.
Optical rotations were measured with a Perkin-Elmer model 241 polarimeter ꢀ20ꢃC, 589 nm, length
of cuvette: 1 dm). Reactions were monitored by TLC on silica gel GF254 ꢀMerck) with detection
under UV and by charring with 10% H2SO4 in EtOH and subsequent heating. Flash column
chromatography was performed on silica gel 60 ꢀ40±63 ꢃm, Merck). NMR spectra were recorded on
Bruker AMX 400 or Bruker DRX 500 instruments. Chemical shifts are given relative to the solvent
1
1
peaks of CDCl3 ꢀ7.24 ppm for H, 77.0 ppm for 13C) or acetone-D6 ꢀ2.04 ppm for H, 29.3 ppm for
13C). Where necessary, assignments were based on COSY experiments. IR spectra were taken with
an ATI Mattson instrument, Genesis Series ꢀKBr). MALDI-TOF mass spectra were measured with a
Bruker Bi¯ex III with 19 kV acceleration voltage. DHB ꢀc ˆ 10 ꢃg=mm3 in 40% CH3CN=H2O) was
used as the matrix. Ionization was effected with a nitrogen laser at 337 nm.
4-Isothiocyanatobenzyl 2,3,4,6-tetra-O-acetyl-mannopyranoside ꢀ5; C22H25NO10S)
To a solution of 1-O-ꢀ2,3,4,6-tetra-O-acetyl-ꢁ-D-mannopyranosyl)-trichloroacetimidate ꢀ2.8 g,
5.85 mmol) and 4-isothiocyanatobenzylalcohol ꢀ1.0 g, 6.14 mmol) in 25 cm3 dry CH2Cl2, two drops
of TMS-OTf were added under an Ar atmosphere. The reaction mixture was then stirred for two days
at room temperature. The reaction was stopped by addition of 1 cm3 triethylamine. After evaporation
of the solvent, the crude product was puri®ed by ¯ash column chromatography to give an amorphous
yellowish solid.
1
Yield: 43%; IR ꢀKBr): ꢄNCS ˆ 2123 cmÀ1; H NMR ꢀ400 MHz, CDCl3): ꢀ ˆ 7.30 ꢀd, 2H, Har),
7.20 ꢀd, 2H, Har), 5.33 ꢀdd, 1H, H-3), 5.27 ꢀt, 1H, H-4), 5.24 ꢀdd, 1H, H-2), 4.83 ꢀd, 1H, H-1), 4.67
ꢀd, 1H, benzyl-CHH0), 4.51 ꢀd, 1H, benzyl-CHH0), 4.25 ꢀdd, 1H, H-6), 4.04 ꢀdd, 1H, H-60), 3.95 ꢀddd,
1H, H-5), 2.11, 2.08, 2.01, 1.96 ꢀeach s, each 3H, 4 OAc) ppm; 3J1;2 ˆ 1:5, 3J2;3 ˆ 3:6, 3J3;4 ˆ 9:6,
J4;5 ˆ 9:6, J5;6 ˆ 5:1, J5;6 ˆ 2:5, J6;6 ˆ 12:2 Hz; 13C NMR ꢀ100.61 MHz, CDCl3): ꢀ ˆ 170.54,
3
3
3
2
0
0
169.97, 169.88, 169.65 ꢀCˆO), 135.78 ꢀNCS), 135.47 ꢀOCH2Car), 131.09 ꢀN±Car), 129.13
ꢀOCH2CarꢀCar)2), 125.87 ꢀN±CarꢀCar)2), 96.73 ꢀC-1), 69.42, 68.96, 68.77, 66.02 ꢀC-2, C-3, C-4, C-5),
68.81 ꢀCH2), 62.36 ꢀC-6), 20.81, 20.70, 20.62 ꢀ4 CꢀO)CH3) ppm.
General procedure for the preparation of thiourea-bridged homodimers ꢀ1a±6a)
A solution of 2.2 equivalents of the sugar isothiocyanate in 10 cm3 dry CH2Cl2 was heated to re¯ux
temperature under a N2 atmosphere. Then, a solution of 1,8-diamino-3,6-oxaoctane ꢀ1 equivalent in
the 500-fold volume of dry CH2Cl2) was added dropwise. The course of the reaction was monitored
by TLC ꢀtoluene=ethylacetate mixtures). After the reaction was complete ꢀ2±6 h) the solvent was
removed in vacuo and the crude product was puri®ed by ¯ash column chromatography.
1
1a ꢀC36H54N4O20S2): H NMR ꢀ500 MHz, acetone-d6): ꢀ ˆ 7.45 ꢀs, 2H, sugar-NH), 7.33 ꢀs, 2H,
NH), 5.87 ꢀs, 2H, H-1), 5.35 ꢀt, 2H, H-3), 5.06±4.92 ꢀm, 4H, H-2, H-4), 4.25 ꢀd, 2H, H-6), 4.05 ꢀdd,
2H, H-60), 3.97 ꢀbd, 2H, H-5), 3.83±3.66 ꢀbd, 4H, HN±CH2), 3.66±3.52 ꢀbm, 8H, HNCH2CH2OCH2,
3
3
HNCH2CH2), 2.00, 1.99, 1.98, 1.94 ꢀeach s, each 6H, 8 OAc) ppm; J2;3 ˆ 9:8, J3;4 ˆ 9:8,
J4;5 ˆ 9:8, J5;6 ˆ 2:2, J6;6 ˆ 12:3 Hz; 13C NMR ꢀ125.76 MHz, acetone-d6): ꢀ ˆ 184.69 ꢀCˆS),
3
3
2
0
0
170.18, 170.10, 169.62, 169.54 ꢀCˆO), 82.48 ꢀC-1), 73.38, 73.29, 71.09, 68.70 ꢀC-2, C-3, C-4, C-5),

Reactivity of Functionalized Saccharides
481
70.30 ꢀHNCH2CH2O), 69.16 ꢀHNCH2CH2OCH2), 62.09 ꢀC-6), 44.75 ꢀHNCH2), 20.15, 20.10, 20.06,
‡
19.99 ꢀ8 CꢀO)CH3) ppm; MALDI-TOF-MS: m=z ˆ 927.35 [M ‡ H] ꢀcalcd.: 927.29), 949.47
‡
‡
[M ‡ Na] ꢀcalcd.: 949.27), 965.47 [M ‡ K] ꢀcalcd.: 965.24).
2a ꢀC36H54N4O20S2): 1H NMR ꢀ500 MHz, acetone-d6): ꢀ ˆ 8.06 ꢀd, 2H, sugar-NH), 7.34 ꢀs, 2H,
NH), 5.99 ꢀs, 2H, H-1), 5.36±5.30 ꢀm, 4H, H-2, H-3), 5.24 ꢀt, 2H, H-4), 4.27 ꢀdd, 2H, H-6), 4.08 ꢀdd,
2H, H-60), 4.00 ꢀbd, 2H, H-5), 3.84±3.69 ꢀbs, 4H, HNCH2), 3.69±3.56 ꢀbm, 8H, HNCH2CH2OCH2,
3
3
3
HNCH2CH2), 2.12, 2.02, 2.01, 1.96 ꢀs, each 6H, 8 OAc) ppm; J2;3 ˆ 3:2, J3;4 ˆ 9:2, J4;5 ˆ 9:2,
J5;6 ˆ 5:1, J5;6 ˆ 2:5, J6;6 ˆ 12:0 Hz; 13C NMR ꢀ125.76 MHz, acetone-d6): ꢀ ˆ 184.36 ꢀCˆS),
3
3
2
0
0
170.30, 169.81, 169.73, 169.55 ꢀCˆO), 80.45 ꢀC-1), 70.36 ꢀHNCH2CH2O), 70.11, 69.57, 69.21,
66.81, ꢀC-2, C-3, C-4, C-5), 69.21 ꢀHNCH2CH2OCH2), 62.56 ꢀC-6), 44.88 ꢀHNCH2), 20.20, 20.14,
‡
20.05 ꢀ8 CꢀO)CH3) ppm; MALDI-TOF-MS: m=z ˆ 927.29 [M ‡ H] ꢀcalcd.: 927.29), 949.34
‡
‡
[M ‡ Na] ꢀcalcd.: 949.27), 965.31 [M ‡ K] ꢀcalcd.: 965.24).
1
3a ꢀC44H70N4O20S2): H NMR ꢀ400 MHz, CDCl3): ꢀ ˆ 6.91 ꢀbs, 4H, NH), 5.32±5.18 ꢀm, 6H
H-2, H-3, H-4), 4.88 ꢀd, 2H, H-1), 4.24 ꢀdd, 2H, H-6), 4.09 ꢀdd, 2H, H-60), 4.01 ꢀddd, 2H, H-5),
3
3.82±3.51 ꢀm, 28H, spacer-CH2), 2.13, 2.07, 2.02, 1.96 ꢀs, each 6H, 8 OAc) ppm; J1;2 ˆ 1:5,
J2;3 ˆ 3:1, J3;4 ˆ 10:2, J4;5 ˆ 10:2, J5;6 ˆ 5:1, J5;6 ˆ 2:6, J6;6 ˆ 12:2 Hz; 13C NMR
3
3
3
3
3
2
0
0
ꢀ100.61 MHz, CDCl3): ꢀ ˆ 170.73, 170.39, 170.04, 169.73 ꢀCˆO), 97.49 ꢀC-1), 70.00, 69.91,
69.82 ꢀspacer-OCH2), 69.66, 69.00, 68.43, 66.11 ꢀC-2, C-3, C-4, C-5), 67.02 ꢀsugar-OCH2), 62.48
ꢀC-6), 44.34 ꢀCH2NHCSNHCH2), 20.93, 20.74, 20.69 ꢀ8 CꢀO)CH3) ppm; MALDI-TOF-MS:
‡
‡
m=z ˆ 1103.31 [M ‡ H]
ꢀcalcd.: 1103.39), 1125.35 [M ‡ Na]
ꢀcalcd.: 1125.37), 1141.34
‡
[M ‡ K] ꢀcalcd.: 1141.35).
1
4a ꢀC34H54N4O18S2): H NMR ꢀ400 MHz, CDCl3): ꢀ ˆ 5.30 ꢀdd, 2H, H-3), 5.19 ꢀdd, 2H, H-2),
5.13 ꢀt, 2H, H-4), 4.65 ꢀd, 2H, H-1), 4.08 ꢀbd, 2H, H-6), 4.00 ꢀbd, 2H, H-60), 3.92 ꢀddd, 2H, H-5),
3.66±3.61 ꢀbq, 4H, HNCH2), 3.61±3.47 ꢀbm, 8H, HNCH2CH2OCH2, HNCH2CH2), 3.36 ꢀs, 6H,
3
3
3
3
OCH3), 2.12, 2.06, 1.96 ꢀs, each 6H, 6 OAc) ppm; J1;2 ˆ 1:5, J2;3 ˆ 3:6, J3;4 ˆ 9:7, J4;5 ˆ 9:7,
J5;6 ˆ 6:6, J5;6 ˆ 2:0 Hz; 13C NMR ꢀ100.61 MHz, CDCl3): ꢀ ˆ 170.28, 170.05, 169.83 ꢀCˆO),
3
3
0
98.37 ꢀC-1), 69.95 ꢀHNCH2CH2O), 69.87 ꢀHNCH2CH2OCH2), 69.59, 69.13, 68.79, 67.15 ꢀC-2, C-3,
C-4, C-5), 55.33 ꢀOCH3), 45.33 ꢀC-6), 44.37 ꢀHNCH2), 20.88, 20.83, 20.66 ꢀ6 CꢀO)CH3) ppm;
‡
‡
MALDI-TOF-MS: m=z ˆ 871.10 [M ‡ H] ꢀcalcd.: 871.30), 893.13 [M ‡ Na] ꢀcalcd.: 893.28),
‡
909.10 [M ‡ K] ꢀcalcd.: 909.25).
5a ꢀC50H66N4O22S2): 1H NMR ꢀ500 MHz, CDCl3): ꢀ ˆ 7.33 ꢀd, 4H, Har), 7.14 ꢀd, 4H, Har), 5.33
ꢀdd, 2H, H-3), 5.29±5.24 ꢀm, 4H, H-2, H-4), 4.88 ꢀd, 2H, H-1), 4.69 ꢀd, 2H, benzyl-CHH0), 4.51 ꢀd,
2H, benzyl-CHH0), 4.26 ꢀdd, 2H, H-6), 4.08 ꢀdd, 2H, H-60), 4.00 ꢀddd, 2H, H-5), 3.82±3.68 ꢀbs, 4H,
HNCH2), 3.66±3.52 ꢀm, 8H, HNCH2CH2O, HNCH2CH2OCH2), 2.12, 2.09, 2.01, 1.96 ꢀeach s, each
0
6H, 8 OAc) ppm; 3J1;2 ˆ 1:5, 3J2;3 ˆ 3:5, 3J3;4 ˆ 10:1, 3J4;5 ˆ 10:1, 3J5;6 ˆ 5:1, 2J5;6 ˆ 2:2 Hz; 13
C
NMR ꢀ125.76 MHz, CDCl3): ꢀ ˆ 170.59, 170.04, 169.94, 169.64 ꢀCˆO), 129.39 ꢀCarN0H), 128.98
0
0
ꢀCarCH2O), 128.17 ꢀCa;a CarCH2O), 124.41 ꢀCx;x CarNH), 96.82 ꢀC-1), 70.17 ꢀHNCH2CH2O), 69.48
ꢀHNCH2CH2OCH2), 69.10 ꢀCarCH2), 69.48, 69.00, 68.73, 66.08 ꢀC-2, C-3, C-4, C-5), 62.42 ꢀC-6),
44.93 ꢀHNCH2), 20.84, 20.73, 20.65 ꢀ8 CꢀO)CH3) ppm; MALDI-TOF-MS: m=z ˆ 1139.11
‡
‡
‡
[M ‡ H] ꢀcalcd.: 1139.37), 1161.18 [M ‡ Na] ꢀcalcd.: 1161.35), 1177.14 [M ‡ K] ꢀcalcd.:
1177.32).
1
6a ꢀC48H62N4O22S2): H NMR ꢀ500 MHz, CDCl3): ꢀ ˆ 8.12 ꢀs, 2H, ar-NH), 6.40 ꢀs, 2H, NH),
7.12 ꢀd, 4H, Har), 7.05 ꢀd, 4H, Har), 5.52±5.46 ꢀm, 4H, H-1, H-3), 5.38 ꢀdd, 2H, H-2), 5.33 ꢀt, 2H,
H-4), 4.22 ꢀdd, 2H, H-6), 4.07±3.99 ꢀm, 4H, H-5, H-60), 3.71 ꢀbs, 4H, HNCH2), 3.55 ꢀbs, 4H,
HNCH2CH2OCH2), 3.50 ꢀbs, 4H, HNCH2CH2O), 2.15, 2.01, 1.99, 1.98 ꢀeach s, each 6H, 8 OAc)
ppm; J3;4 ˆ 9:8, J4;5 ˆ 9:8, J5;6 ˆ 5:4, J6;6 ˆ 12:6 Hz; 13C NMR ꢀ100.61 MHz, CDCl3):
3
3
3
2
0
ꢀ ˆ 180.81 ꢀCˆS), 170.37, 169.90, 169.83, 169.52 ꢀCˆO), 153.95 ꢀCar±O), 131.36 ꢀCar±NH),
0
126.53 ꢀHN±CarCx;x ), 117.45 ꢀO±CarCa;a ), 95.79 ꢀC-1), 70.02 ꢀHNCH2CH2O), 69.20
0
ꢀHNCH2CH2OCH2), 69.12, 69.08, 68.63, 65.61 ꢀC-2, C-3, C-4, C-5), 61.87 ꢀC-6), 44.69 ꢀHNCH2),
‡
20.73, 20.53 ꢀ8 CꢀO)CH3) ppm; MALDI-TOF-MS: m=z ˆ 1111.25 [M ‡ H] ꢀcalcd.: 1111.34),
‡
‡
1133.09 [M ‡ Na] ꢀcalcd.: 1133.32), 1149.01 [M ‡ K] ꢀcalcd.: 1149.29).

482
M. Walter and T. K. Lindhorst
General procedure for the competition experiments
Under a N2 atmosphere, 2 equivalents of each of the two competing sugar isothiocyanates were
dissolved in 10 cm3 dry CH2Cl2 at re¯ux temperature. Then, a solution of 1,8-diamino-3,6-oxaoctane
ꢀ1 equivalent in a 500-fold volume of dry CH2Cl2) was added dropwise. Progress of the reaction was
monitored by TLC ꢀtoluene=ethylacetate mixtures). After the reaction was complete ꢀ2±6 h) the
solvent was removed in vacuo and the crude product was puri®ed by ¯ash column chromatography.
Mixed glycocluster ꢀ7; C59H91N7O31S3)
Under a N2 atmosphere, 2 ꢀ28 mg, 0.07 mmol, 0.33 equiv. per amino group) and 3 ꢀ1.06 g,
3
2.20 mmol, 16 equiv. per amino group) were dissolved in 15 cm dry CH2Cl2. To this solution, tris-
ꢀ2-aminoethyl)-amine ꢀ10 mg, 0.07 mmol, dissolved in 0.5 cm3 of dry CH2Cl2) was added dropwise.
This mixture was then heated under re¯ux for 3 h. After the removal of the solvent, the excess educts
were separated from the products by ¯ash column chromatography. The product mixture was then
analyzed by MALDI-TOF-MS.
‡
MALDI-TOF-MS: m=z ˆ 1402.75 ꢀ[ꢀ2)2ꢀ3)1-cluster ‡ H] , 30%, calcd.: 1402.45 for C55H83N7
‡
O29S3 ꢀM ˆ 1401.44)), 1490.86 ꢀ[ꢀ2)1ꢀ3)2-cluster ‡ H] , 57%, calcd.: 1490.50 for C59H91N7O31S3
‡
ꢀM ˆ 1489.49)), 1578.98 ꢀ[ꢀ3)3-cluster ‡ H] , 13%, calcd.: 1578.55 for C53H99N7O33S3 ꢀM ˆ
1577.54)).
Acknowledgements
This work was kindly supported by the Fonds der Chemischen Industrie and the Karl-Ziegler-
Stiftung.
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Received June 13, 2001. Accepted October 31, 2001