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Gas Chromatographic Separation of Carbohydrate Enantiomers on a New Chiral Stationary Phase.

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A comparison of these lattice constants with the values
expected for the theoretically predicted structural possibilitied3’suggests the likelihood of a structure type containing
cyclic ( M o C I ~molecules.
)~
An analysis of the intensities on
the diffuse lines according to a recently described method”] confirms this (refinement to R=7.2% for 226 measured points on diffuse lines and R =2.8% for 155 sharp reflections).
Our structural model shows that P-MoC1, is made up of
hexameric cyclic molecules (MOC& (Fig. 1). The bond
lengths are: Mo-CI,,,,,,,,
220, Mo-CI,,,,,,
243 and 251
pm. The molecules are arranged in layers (parallel to the
plane of the picture in Figure 1. The stacking of the layers
is disordered, but in such a way that the C1 atoms assume
an hexagonal closest-packed arrangement. The pairwise
closing up of metal atoms between adjacent octahedra,
which is often observed in compounds of metals with electron configuration d ’ and d2, is not apparent here, the
Mo- . . M o distances of 367 pm are too large for any notable interactions between the metal atoms ; this is consistent
with the known magnetic properties”], which indicate a
virtually undistorted d’-configuration.
Although molybdenum tetrachloride has already been
known for some time and has been the subject of repeated
investigations, nothing has previously been mentioned
about its ability to form hexameric molecules. There is as
yet no other such example of a structure of this kind.
Received: January 29, 1981 [ Z 822 IE]
German version: Angew. Chem. 93, 697 (1981)
CAS Registry number:
(MoCI&, 78456-38-9.
acid esters and separation of the acetylated derivativesf4].
In a similar procedure the preparation of diastereomeric
derivatives was achieved by glycosidation with (-)-2-butano1 and separation of the trimethylsilylated derivatives on
glass capillary columns151.In addition to the difficulties involved with the derivatization, the quantitative determination of enantiomers via formation of diastereomeric derivatives suffers from a systematic error arising from the incomplete purity of the chiral reagents.
We have now for the first time prepared a temperaturestable chiral stationary phase which allows the separation
of volatile derivatives of carbohydrate enantiomers. This
involves the saponification of methyl(cyanoethy1)silicone
XE-60I6] with alkali and coupling the carboxylic groups
formed to L-valine-(S)-a-phenylethylamide by conventional methods. Glass capillaries were coated with this
modified polymer and trifluoroacetylated sugars[71or their
methyl glycosides separated. Columns prepared according
to this procedure did not exhibit a reduction in their separation efficiency after continuous operation at temperatures up to 180 ’C over several weeks.
Trifluoroacetylation of sugars (TFA = trifluoracetyl) resulted in an isomeric mixture of a-and j3-furanosides and
a- and 0-pyranosides, which were identified by G U M S in~estigation~~’.
The TFA-methyl glycosides (prepared by
reaction of the sugars with methanolic 1 . 5 HCl
~
at 100°C
and subsequent trifluroacetylation) formed isomeric mixtures corresponding in composition to literature data“’ and
were identified by measurement of their peak areas. The
results are presented in Table 1 and in some examples in
Figure 1. The TFA-groups appear to be essential for the
separation, since trimethylsilyl derivatives of the sugars
with comparable volatility are not separated.
[ I 1 D. L Kepert. R . Mandyczewsky. Inorg. Chem. 7. 2091 (1968).
12) H. Schafer. H. G . von Schnering, J. Tillack, F. Kuhnen, H. Wohrle. H.
Baumann. Z. Anorg. Allg. Chem. 353, 281 (1967).
131 U. Miiller, Acta Crystallogr. 837, 532 (1981).
141 H . Jogodzinski, Acta Crystallogr. 2, 201, 209 (1949).
151 U . Miiller. Acta Crystallogr. A35, 957 (1979).
Gas Chromatographic Separation
of Carbohydrate Enantiomers
on a New Chiral Stationary Phase
Table I. Gas chromatographic enantiomer separation of carbohydrates on a
glass capillary column coated with XE-60-L-valine-(S)-a-phenylethylamide
(TFA = trifluoroacetyl, P = pyranoside, F = furanoside). For conditions see
Figure 1.
Sugar
Separation Factor a/Column Temperature [“C)
TFA-Derivative
TFA-Methyl Glycoside
Glucose
a-(P)
By WiIfried A . Konig, Ingrid Benecke, and
Hagen Bretting[’I
Mannose
Micromethods for the configurational analysis of low
molecular weight chiral compounds are essential for the
structural elucidation of natural products[’.’].
While the problem of the gas chromatographic determination of the configuration of the constituents of peptides
and proteins seems to be solved[*’,this is not the case with
the constituents of polysaccharides. Since in nature sugars
occur rather more frequently than amino acids in both
configuration^'^^, a simple gas chromatographic procedure
would be of interest for their analysis.
As early as 1968 Poiiock and Jermany suggested a
method involving oxidation of aldoses to aldonic acids, esterification with a chiral alcohol to diastereomeric aldonic
Galactose
[*I
Prof. Dr.W. A. Konig, DipLChem. I. Benecke
Institut fur Organische Chemie und Biochemie der Universitat
Martin-Luther-King-Platz 6, D-2000Hamburg 13 (Germany)
Dr.H. Bretting
Zoologisches Institut und Zoologisches Museum der Universitat
Martin-Luther-King-Platz 3, D-2000Hamburg 13 (Germany)
Angeus. Chem. I ~ Ed.
I . Engl. 20 (1981) No. 8
1.071/140
1.044/140
(F)
(F)
1.031/140
B-(P)
a-(P)
(F)
B-(P)
a-(P)
(F)
B-(P)
(F)
Xylose
Arabinose
B-(P)
[a]
[a]
[a]
[a]
Fucose
I .032/120
1 . 0 3 120
~
1.140/140
1.036/140
1.045/140
1.247/140
1.019/140
1.019/140
1.045/140
1.029/140
1.030/100
1.028/100
1.017/100
1.048/100
1.026/100
1.053/120
1.0841120
1.010/120
1.044/120
1.049/120
1.089/I20
-
1.019/100
1.023/100
I .046/100
-
-
-
-
[a] 1.035/100
1.014/100
1.046/100
[a] Designation uncertain.
The order of elution of enantiomers is not identical in all
the examples investigated. In the case of TFA-derivatives
of glucose and mannose and in that of the TFA-methyl
glycosides, the L-enantiomers eluted before the D-enantiomers: the same order was observed for the first three
isomeric pairs of TFA-arabinose, however, for the pair
0 Verlag Chemie GmbH, 6940 Weinheim. 1981
OS70-0833/81/0808-0693 $02.50/0
693
with the longest retention time the order of elution is reversed (Fig. 1).
[21 E. Gil-Av, B. Feibusk, R . Charles-Sigler in A . B. Littlewood: Gas Chromatography 1966, Institute of Petroleum, London 1967, p. 227; W. A. Konig,
G. J. Nickolson. Anal. Chem. 47, 951 (1975); U. Beitler, B. Feibush. J.
Chromatogr. 123. 149 (1976); S. Weinstein, B. Feibush. E. Gil-Av. ;bid.
126, 97 (1976); H . Frank, G. J . Nicholson, E. Buyer, Angew. Chem. 90,
396 (1978); Angew. Chem. Int. Ed. Engl. 17, 363 (1978).
I31 J. Stanek, M . Cemy. J . Kocourek, 1. Pacak: 7he Monosaccharides, Academic Press, New York 1963.
[41 G . E. Pollock, D. A . Jermany, J. Gas Chromatogr. 6, 412 (1968); J. Chromatogr. Sci. 8. 296 (1970).
[51 G. J. Genuig. J. P. Kamerling, J. F, G. Yliegenrhart, Carhohydr. Res. 62,
349 (1978).
161 Supplier, Macherey, Nagel & Co., D-5160 Duren (Germany).
[71 W. A . Kiinig. H . Bauer. W. Voelter, E. Bayer, Chem. Ber. 106. 1905
(1973).
I81 J. Lehmann: Chemie der Kohlenhydrate, Thieme, Stuttgart 1976, p. 94.
191 D. J . Bell, E. Baldwin, J. Chem. SOC.143, 125 (1941).
Or-P
L
'
--*
10
5
-
10
5
Reaction of Dibenzoyldiazomethane
with 1-Diethylaminopropyne
t (rninl
Fig. 1. Separation of carbohydrate enantiomers. a) TFA-derivatives of arabinose isomers, h) TFA-derivatives of a-and b-methylpyranosides of glucose.
Glass capillary column (horosilicate glass, 40 m, 0.2 mm inner diameter) with
XE-60-L-valine-(S)-a-phenylethylamide.T= 100 "C, temperature program
3"C/min. (Carlo Erha 2101 A gas chromatograph, carrier gas: 0.7 bar HZ.)
P = pyranoside, F= furanoside.
By Rorf Huisgen, Maria Pilar Bosch Verderol,
Arfred Gieren, and Viktor Lamrn["
Dedicated to Professor Siesfried Hiinig on the occasion
of his 60th birthday
Dimethyl diazomalonate combines with l-diethylaminopropyne at room temperature to give the 3H-pyrazole derivative ( I ) , which is converted into the pyrazole-1,5-dicarboxylic ester (3) by a 1,5-sigmatropic shift of an ester group
(tl,z-30 days at 25 "C in CDCl,)"]; this aromatization of
3H-pyrazoles is known as the van-Alphen-Hiittel rearrangement[''.
R
For galactose and fucose (6-deoxygalactose), in any
case, the D-enantiomers are eluted prior to the L-enantiomers. The TFA-methyl glycosides of xylose (a-and p-pyranoses) are not separated. In the TFA-derivatives only
one pair of enantiomers is separated (P-pyranoses). As in
the case of glucose the L- is eluted before the D-form.
oc/
a-P
1
L
bl
( 1)
i
I
D 0-F
i
J
(3)
14)
R = OCH,
R = C~HS
f 2)
As expected, the cycloaddition of dibenzoyldiazomethane to the same ynamine is slower, and the ensuing sigmatropic shift faster, than in the preceding example. The reaction of equimolar amounts in benzene (8 days, 20 C, chromatography on silica gel) yielded 66% (4) (orange yellow
needles, m.p. 74-75 "C) and 13% of a yellow 1 :2 adduct
(m.p. 84-85 "C); the primary adduct (2) was not detected.
Different signals for ketone carbonyl (6= 188.1) and amide
carbonyl C-atoms (6= 165.2) appear in the I3C-NMR spectrum (CDCl,) of (4). and the chemical shifts of the ring
carbon atoms (6 = 152.1, 137.4, 136.6) correspond to those
of (3) (S=149.3, 134.4, 130.9). The carbonyl frequencies of
(4) absorb at 1670 and 1697 cm-'. The aminolysis of (4) in
refluxing diethylamine produced (5) and N,N-diethylbenzamide quantitatively.
O
D
15
-t
10
s
L
(rnin)
Fig. 2. Separation of TFA-methyl galactoside enantiomers: a) acid hydrolysate of Helix pomatia galactan, b) reference mixture of D- and L-galactose
derivatives. For conditions, see Figure I .
The utility of the new method may be demonstrated by
the investigation of a hydrolysate of the galactan of the
snail Helix pomatia. This high molecular, branched polysaccharide consists of D- and L-galactose. The chromatographic separation of the TFA-methyl glycosides and the
electronic integration of peak areas of the a- and P-pyranosides, which are well separated (Fig. 2), showed that the
galactan contains 14.4% L-galactose. This result is in agreement with measurements of the optical rotation by Bell
and Baldwin[".
Received: February 24, 1981 [ Z 805 IEI
German version: Angew. Chem. 93, 688 (1981)
Ill W . A . Konig. S. Sieuers, U Schulze, Angew. Chem. 92, 935 (1980); Angew. Chem. Int. Ed. Engl. 19, 910 (1980); W. A . Konig, S. Sieuers, J.
Chromatogr. 200. 189 (1980).
694
0 Verlag Chemie GmbH. 6940 Weinheim, 1981
H
(5)
[*] Prof. Dr. R. Huisgen, Dr. M. P. Bosch Verderol
Institut fur Organische Chemie der Universitat
Karlstr. 23, D-8000 Munchen 2 (Germany)
Dr. hahil. A. Gieren, Dipl.-Phys. V. Lamm
Max-Planck-Institut fur Biochemie
Abteilung fur Strukturforschung I
D-8033 Martinsried (Germany)
0570-0833/81/0808-0694 S 02.50/0
Angew.
Chem. Int. Ed. Engl. 20 (1981) No. 8
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