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Facile Synthesis of a (1-3)-Linked gal-galactal Disaccharide and Its Use in N-Iodosuccinimide-Activated O-Glycopeptide Synthesis.

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were completely replaced within 1 h by a new set of signals
attributable to the expected selenepine 1 c without evidence
of other products (see Table 1). When the solution was allowed to warm to room temperature, l c extruded selenium
to give diethyl 4,5-di-tert-butylphthalate (9) quantitatively;
this reaction is consistent with the structure of 1c. Nonetheless, attempted isolation of pure 1 c met with failure due to
contamination with 9 even at low temperature. This provides
a striking contrast to the pronounced thermal stabilities of
2,7-di-tert-butylthiepineand its derivative^.^^]
The clean extrusion of selenium from l c to give 9 obeys
first-order kinetics in the temperature range 15-35 "C
('H-NMR monitoring in CDCl,).['] An Arrhenius plot of
the data gives the following approximate activation parameters: AH* = 26 kcal mol-', E, = 26 kcalmol-', A S * =
9.3J K - ' .
The corresponding activation parameters for the sulfur
extrusion reaction of ethyl 2,7-di-tert-butyl-5-methyl-4thiepinecarboxylate (10) are AH* = 22.4 & 3.4 kcal mol-l,
and A S * = -26.9 _+ 3.7 J
E, = 23.3 f 3.4 kcal mol-',
K- '.191 Most conspicuous is the large difference in the activation entropies. The large negative A S * value for the
thiepine can be attributed to severe nonbonding interaction
between two tert-butyl groups in a thianorcaradiene intermediate.["] On the other hand, the selenium extrusion reaction of the selenepine 1 c presumably proceeds via incipient
fission of a C-Se bond, whereby the bulky tert-butyl groups
at the 2- and 7-positions do not play a decisive role. The
detailed pathway of the selenium-extrusion reaction must
await further study. Nonetheless, our work clearly shows
that, although detailed studies on selenophene have confirmed its striking similarity to thiophene, the thermal stability of the vinylogous selenepine is markedly different from
that of thiepine.
Received: November 7, 1989 [Z 3623 IE]
German version: Angew. Chem. 102 (1990) 450
[l] Selected reviews: a) A. R. Katritzky (Ed.): Comprehensive Heterocyclic
Chemistry, Vol. 4 - 6 , Pergamon Press, Oxford 1984; b) D. R. Hogg (Ed.):
Organic Compounds of Sulfur. Selenium and Tellurium, Vol. 2 (1972), Vol. 3
(1975). Vol. 4 (1977), Vol. 6 (1981), Chem. SOC.,London.
[2] M. Renson in S. Patai, Z . Rappoport (Ed.): The Chemistry ofSelenium and
Tellurium Compounds, Vol. 1, Wiley, New York 1986, pp. 399-516.
[3] K. Sindelar. J. Metysova, M. Protiva, Collect. Czech. Chem. Commun. 34
(1969) 3801; J Jilek, K. Sindelar, J. Metysova, J. Metys, J. Pomykaek, M.
Protiva, ibid. 35 (1970) 3721.
[4] Attempted detection of a 2,7-diisopropylthiepine derivative: S . Yano, K.
Nishino, K. Nakasuji, I. Murata, Chem. Lett. 1978, 723.
[5] a) K. Nishino, S . Yano, Y. Kohashi, K. Yamamoto, 1. Murata, J. Am.
Chem. Soc. 101 (1979) 5059; b) I. Murata, K. Nishino, S. Yano, Y Kohashi, K. Yamamoto, Croat. Chem. Acta 53 (1980) 615, c) K. Yamamoto,
S . Yamazaki, Y. Kohashi, A. Matsukawa, I. Murata, Chem. Lett. 1982,
1843; K. Yamamoto, S. Yamazaki, Y. Kohashi, I. Murata, Y Kai. N.
Kanehisa, K. Miki, N. Kasai, Tetrahedron Lett. 23 (1982) 3195; d) K.
Yamamoto, A. Matsukawa, I. Murata, Chem. Lett. 1985, 1119.
[6] K. Yamamoto. S . Yamazaki, H. Osedo, I. Murata, Angew. Chem. 98 (1986)
639. Angew. Chem. Int. Ed. Engl. 25 (1986) 635.
171 M. R. Detty, J. W. Hassett, B. J. Murray, G. A. Reynolds, Tetrahedron. 41
(1985) 4853: M. R. Detty, B. J. Murray, M. D. Seidler, J Org. Chem 47
(1982) 1968.
[S] The disappearance of 1c and the appearance of9 were monitored by NMR
integration. The first-order rate constants are k293= 2 . 0 0 ~
k 3 0 3= 9 . 1 0 ~
s - ' , k''* = 2.03 x
sC1, and k3" = 4.12 x
191 The disappearance of 10 and the appearance of ethyl 4.5-di-rert-butyl-2methylbenzoate were monitored by NMR integration. The first-order rate
s-', k4I3= 1 . 5 6 ~
constants in [D,Jdecalin are k4O' = 1 . 0 7 ~
s - ' , k 4 2 5= 3.29 x
sC1, and k434 = 6 . 6 6 ~
[lo] R. Gleiter, G. Krennrich, D. Cremer, K. Yamamoto, I. Murata, J Am.
Chem. SOC.107 (1985) 6874.
AnKen.. Chem. I n t . Ed. Engl. 29 ( i 9 9 0 ) No. 4
Facile Synthesis of a P(13)-Linked
gal-galactal Disaccharide and Its Use
in N-Iodosuccinimide-Activated
0-Glycopeptide Synthesis **
By Horst Kessler,* Andreas Kling, and Matthias Kottenhahn
a-0-Glycopeptides with gal-p(1-3)-galNAc disaccharide
building blocks are widespread in Nature.I'] The disaccharide gal-P(1-3)-galNAc forms the core A of many O-glycopeptides, and, moreover, has been identified as the immune-determining structural unit of a tumor associated
antigen, of the so-called T-antigen (Thomson-Friedenreich
antigen).['] Since T-specific immunoreactive structural units
have been detected in certain types of carcinoma but not in
healthy tissues, the T/anti-T system could prove useful in the
diagnostics of cancerous diseases.[3]The keen interest being
shown in T-antigen structures is evident from the numerous
works on the synthesis of the core A d i ~ a c c h a r i d e and
corresponding O-gly~opeptides.~~~
In our investigations of the synthesis of 2-deoxyglycopeptides by N-iodosuccinimide(N1S)-activated addition of amino acids and peptides as glycosyl acceptors to glycalsr6.'I we
therefore also checked the addition of amino acid derivatives
to the gal-P(l-3)-galactal building block 1 (Fig. 1).
I, R = Bzl
Fig. 1. Protected gal-~(1,3)-galactaldisaccharide
A twelve-step synthesis of the disaccharide 2 (1 1.5- 14 %
overall yield) has already been described by Bencomo,
This route appeared to us to be too
Jacquinet and Sinay.[4b1
tedious for such a small overall yield. Therefore, the strategy
employed in our synthesis of the disaccharide glycal 1 is
based on another concept (Scheme 1).
First, the 3-OH-unprotected galactal derivative 5 is generated by selective benzylation of the 4-OH and 6-OH functions of galactal4. Subsequently, 5 and 3 are coupled under
Koenigs-Knorr conditions to give the disaccharide glycal 1.
The selective introduction of protecting groups into 4 constitutes the major problem of this synthetic concept. According to Kinzy and Schmidt[*]a selective silylation of the 4-OH
and 6-OH functions of galactal4 is not possible; also in the
benzoylation of 4 it emerged that the allylic 3-OH function
is clearly more reactive than the 4-OH function;[91according
to Holla,['ol a selective enzymatic deacetylation of peracetylgalactal is, other than in the case of the glucal analogue,
likewise not possible. In contrast, selective benzylation of the
4-OH and 6-OH functions can be achieved, as shown in
Scheme 1. The byproduct of this reaction is the perbenzylated galactal.
Flowers" 'I had already demonstrated with methylgalactopyranosides that the 4-OH group is more reactive in the
benzylation, and, in 1983, Bovin et a1.['*] described a possible
[*] Prof. Dr. H. Kessler, Dr. A. Kling
Organisch-chemisches Institut der Technischen Universitat Miinchen
Lichtenbergstrasse 4, D-8046 Garching (FRG)
Dr. M Kottenhdhn
Degussa AG, ZN Wolfgang-FCO
Rodenbacher Chaussee 4, D-6450 Hanau l/Wolfgang (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschdft and
the Fonds der Chemischen Industrie. M . K . thanks the Fonds der Chemischen Industrie for a postgraduate study grant.
@) VCH Verlagsgesellschaf~mbH, 0-6940 Weinheim, I990
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a-product 8 (270 MHz 'H-NMR: 3J(l, 2) = 3.78, 3J(2,
3) = 1 1.2 Hz) were formed (Fig. 2). Because of the increased
reactivity of the enolic double bond['21 both possible iodonium structures are formed, thus explaining formation of the
products 6-8. Owing to the high electron density of the
arene substituents on C-4 and C-6, respectively, an opening
of the a-iodonium intermediate to give the C-1 carbocation
can result, whereby formation of the I,2-cis product 8 is
possible. 6 and 8 furnish the same 2-deoxy-a-0-gIycosylamino acid after deiodination.
Scheme 1. Synthesis of the disaccharide glycal 2',3',4,6,-tetra-0-acetyl-~galactopyranosyl-B(t-3)-4.6-di-0-benzyI-~-galactal
1 in 21.3% overall yield in
four steps. a) 1) Zn/glacial acetic acid (90%); 2) KCN/methanol (82%).
b) Dimethylformamide (DMF). 2.2 equiv. NaH, 0"C, 2 h; 2.2 equiv. benzyl
bromide BzLBr, 0°C. 3 h. c) 1.8 equiv. Ag,CO,/O.Z equiv. Ag-triflate, 2.7
equiv. 3, CH,NO,. RT. 2 h.
6 (52%)
7 (lf.S%)
synthesis of 4,6-di-O-benzyl-~-galactalby reaction of galactal with NaH/benzyl bromide, but attached little importance
to this fact, for they synthesized the glycal 5 in eleven steps
with 13.5% overall yield via another route. The entry to 5
according to Scheme 1 seems distinctly superior to such a
complex synthesis.
The coupling of 5 and 3 under Koenigs-Knorr conditions
to give 1 necessitates a careful choice of catalyst. The allylic
enol-acetal structure of the product can easily lead in the
presence of nucleophiles and catalytic amounts of Lewis acid
to side reactions in which complex mixtures of disaccharides
are formed. The combination of reagents quoted in the caption to Scheme 1 have proven to be the most suitable for the
synthesis (Table 1); they afforded 1 in ca. 21 % overall yield.
The disaccharide glycal 1 was now allowed to react under
conditions of NIS activation[6*141 with the amino acid building block Fmoc-Ser-OBzl. Thereby it showed the expected
high reactivity (83.5 YOoverall yield). However, the almost
complete a-diastereoselectivity observed in the addition to
monosaccharide glycalsL6]could not be achieved. Besides the
desired 1,2-truns-a-product 6 (250 MHz 'H-NMR: 3J(l,
2) = 2.7 Hz), both the 3,2-truns-B-product 7 (270 MHz 'HNMR: 3J(l,2) = 9, 3J(2, 3) = 7.4 Hz) as well as the 1,2-cis-
8 (ZOO/)
Fig. 2. Products and yields in the NIS-activated addition of Fmoc-Ser-OBzl to
disaccharide glycal 1.
In immunological tests it could be shown that a partial
structure of asialoglycophorin A with the amino acids 43-48
exhibits a strong T-antigen activity.['51After Puulsen et al.[5'1
had synthesized the linear diglycohexapeptide we directed
our attention to the synthesis of the corresponding cyclic
peptide analogue ~yclo(Val~~-Ser-Glu(OBzl)-Ile-Ser-~Val4') 9 and its conversion into the 2-deoxy-analogue of
the T-antigen by direct glycosidation according to the NIS
The linear hexapeptide was obtained in a convergent synthesis according to the classical methods of peptide chemistry. Subsequent a i d e cyclization [ I 6 ] and HPLC purification
afforded the cyclic hexapeptide 9 in 37 YO
Reactions leading to 0-glycopeptides according to the
NIS method proceed with distinctly better yields at higher
temperatures; nevertheless, the glycosidation of 9 could only
Table 1. Yields and reaction conditions for the reaction of 3 with 5 to give 1. Optimal parameters given in bold print
Catalyst (a]
Yield of I
(Bu,Sn),O WI
1.1 equiv. Ag-triflate
0.9 equiv. Ag,CO,i
0.1 equiv. Ag-triflate
1.8 equiv. Ag,CO,/
0.2 equiv. Ag-triflate
1.8 equiv. Ag,CO,/
0.2 equiv. Ag-triflate
1.8 equiv. Ag,CO,/
0.2 equiv. Ag-triflate
0°C + RT
0 "C + RT
O'C + RT
-40 "C + RT
25.8 Yo
no reaction
no reaction
25 %
no reaction
25 - 30 %
47 %
47.3 %
1 z2.7
[a] Equivalents w.r.t. 5.
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Angew. Chem. I n ( . Ed. Engl. 29 (1990) N o . 4
be carried out at room temperature because of its thermolability. The crude product obtained (33 YOyield) after workupt6]and silica gel filtration (CHClJacetone 4/1, subsequent
elution of the product with 2-propanol) shows exclusively
the molecular peak for a monoglycosidation product
( M + Na@= 1509) in the FAB mass spectrum. Investigations concerning the exact structure are currently under way.
Herein we have described a simple synthesis of the versatile disaccharide glycal 1 and its use in 0-glycopeptide
synthesis. In the case of the addition to Fmoc-Ser-OBzl using
the NIS method, a diastereomeric mixture is formed which
also contains an unexpected cis-addition product. The desired cr-epimer, however, is formed in appreciable excess.
5 ( M = 326.39. C,oH,,O,): A stirred solution of 4 (8.9mmol) in 1 4 m L of
anhydrous D M F under argon was treated at 0 ° C with 19.58 mmol of NaH
(60% in mineral oil). After 2 h at 0 ° C the mixture (suspension) was treated
dropwise and rapidly with 19.58 mol of BzlBr and then allowed to stand for 3 h
at 0 ° C The mixture solidified. It was then thawed out, treated with 50 mL of
benzene. washed with 20 mL of water, the aqueous phase back extracted with
3 x 15 mL of benzene and the combined organic phases finally evaporated to
dryness in a vacuum (water pump). The residue was purified by chromatography on silica gel with ethyl acetdte/isohexane 315. The main fraction contained
(1.4 g = 48.2 Yo)of 5. One secondary fraction (39%) contained perbenzylated
4. a further secondary fraction (8 %) another dibenzylated 4. Oily 5 crystallized
out on cooling the main fraction and could be recrystallized from isohexane.
M.p. = 65 C (68 ‘C [14)], [41” = 12.06 (c = 0.6 in CHCI,) ([I]” =
- 17 [14])(nodetails of temperature and solvent); the rotation quoted by us was
reproduced several times). R, = 0.64 (ethyl acetate/isohexane l / l ) , 0.37 (ethyl
acetatelisohexme li2).-250 MHz ‘H-NMR([D,]DMSO): d = 7.15-7.4 (m,
10H. H,,,,,,), 6.27 (dd, 1 H. H-1, ’J(l.2) = 6.19, 4J(1,3) = 1.75 Hz), 4.86 (d,
1 H. OH-3. ‘J(OH.3) = 5-83), 4.85, 4.5 Oe d, 2 H , Ph/CH,). 4.46 (d, 2 H , PhCH,), 4.63 (ddd. 1 H, H-2, 4J(2.4) = 1.39 Hz), 4.35 (m, 1 H, H-3). 4 14 (m, 1 H,
H-5). 3.72 (dd, 1 H. H-4), 3.7-3.53 (m, 2H. H-6).-75 MHz-”C NMR
(CDCI,): ri = 144.2 (C-1), 137.7 (quarternary C,,,.,,), 127.8- 128.6 (CPhcn,,),
102.9 (C-2). 75.2 (C-5),74.2, 73.5 (Ph-CH,). 73.2 (C-4), 68.1 (C-6). 62.8 (C-3).
1 ( M = 656.68. C,4HduO13):A suspension of 300 mg of molecular sieve,
100 mg of calcined CaSO, and 0.55 mmol of Ag,C0,/0.061 mmol Ag-triflate in
5 mL of nitromethane was prepared in a pre-heated dark glass flask and stirred
for 1 h at room temperature. 0.826 mmol of 3co-evaporated with toluene was
subsequently dissolved in 5 mL of nitromethane and added to the catalyst
suspension at room temperature. After 15 min, solid 5 (0.306 mmol) was added
and the mixture stirred for 2.0-2.5 h. The reaction mixture was now filtered
through celite into an excess of toluene. After evaporation to dryness in a
Rotavapor (35 C) the residue was extracted with diethyl etherlwater. The
residue remaining after evaporation of the diethyl ether phase was chromatographed on silica gel with diethyl etherlisohexane 411. 120 mg of of colorless oil = 60%, [?];’ = -42.5 ( c = 1.3 in CHCI,). R , = 0.23 (diethyl etherlisohexane 4,1).-250 MHz ‘H-NMR(CDCI,, interner standard TMS): 6 =
7.2-7.4 (m. 1OH. Hphcny,),
6.37 (dd, 1 H, H-1. ’J(l.2) = 6.4, 4J(1,3) = 1.9 Hz),
5.4(dd. 1 H, H-4, ’ J ( 4 . 5 ’ ) = 1.5 Hz), 5.27 (dd, 1 H, H-2’. 3J(2’,3’) = 10.45 Hz).
5.03 (dd. 1 H. H-3’. 3J(3’,4) = 3.53 Hz), 4.9, 4.56 (each d, 2 H , Ph-CH,), 4.70
(m. 1 H. H-2, ’J(2.3) = 7.9 Hz), 4.63 (d, 1 H, H-1’. ’J(l’,2’) = 7.97 Hz),4.54(m,
1 H, H-3). 4.42 (dd. 2H, Ph-CH,): 4.14. 4.15 (m, 3 H , H-5. H-6, superposed),
3.91. 3 92 (m. 2 H , H-5’. H-4, superposed) 3.52-3.68 (m, 2H. H-6). 1.95-2.15
( 4 XS, 12H.CO-CH3).-62.9 M H z - ” C N M R ( C D C I , ) . ~ = 169.1-170.3(COCH,). 144.8 (C-1). 137.9-138.5 (quarternary C,,,.,,), 127 5 - 128.3 (C,,,,,,),
99.5 (C-l’).98.4(C-2), 75.75(C-5), 73.2 (Ph-CH,). (C3, C4, C3’, CS),
68.8 (C-2’). 68.4 (C-6), 67.0 (C-4’) 61.2 ( C - 6 ) ,20.5-20.6 (4 x CO-CH,).
Received: November 14. 1989 [Z 36311
German version: Angew. Chem. 102 (1990) 452
CAS Registry numbers:
1,125827-94-3: 3,3068-32-4.4.21 193-75-9; 4 perbenzylated denv., 80040-79-5;
5,81928-98-5: 6.125803-97-6,7.125874-74-0; 9,125874-75.1, Fmoc-Ser-OBzl,
[4] a) H. Paulsen, M. Paal. Curbohydr. Res. 135 (1984) 71-84; b) V. V. Bencomo, J.-C. Jacquinet, P. Sinay. Curbohydr. RPS.110 (1982) C9 C l l
[S] a) H. Paulsen, M. Schultz, J. D. Klamann, B.Waller, M. P a d , Lic4q.Y Ann.
Chem. 1985, 2028-2048; b) H. Paulsen, M. Schultz, ibid. 1986. 14351447; c) H. Paulsen, M. Schultz Curbohydr. Res. 159 (1987) 37- 52; d)
B. Ferrari. A. Pavia, Tetrahedron 41 (1985) 1939-1349; e ) H . Kunz, S
Birnbach, Angew. Chem. 98 (1986) 354-355; Angew. Chem. I n ) . Ed Engl.
2s (1986) 360; f ) W. Kinzy, R. R. Schmidt, Curhohydr. Res. 166 (1987)
[6] H. Kessler, M. Kottenhahn, A. Kling, C. Kolar, Angew. Chem. 99 (1987)
919-921; Angew. Chem. I n / . Ed. Engl. 26 (1987) 888-890.
[7] H. Kessler, M. Kottenhahn in G. Jung, E Bayer (Eds.): Peptides 19XX
(Proc. 20thEur. Pept. Symp), W. de Gruyter, Berlin 1989. S. 331 333.
[XI W. Kinzy, R. R. Schmidt, Tetruhedron Leri 28 (1987) 1981 1984
191 M. Kottenhahn, Disserrution, Universitat Frankfurt 1989.
[lo] W. Holla, Angew. Chem. 101 (1989)222-223; Angew. Chem. In,. Ed. Engl.
28 (1989) 220.
[11] H. M Flowers, Curbohvdr Res. 39 (1975) 245-251.
[12] N. V. Bovin. S. E. Zurabyau, A. Korlin. J. Curhoh.vdr. Chem. 2 (1983)
249 - 262.
[I31 J. C. Jacquinet, P. Sinay, Tetruhedron 35 (1979) 365-371
[14] J. Thiem, H. K. Schwentner, J. Schwentner, Synthesis 1978, 696-698; J
Thiem, M. Gerken, G. Snatzke, Liebigs Ann. Chem. 1983,448 -461
[151 F. G. Hanisch. G H. Farrar, R. Schmalisch, G. Uhlenbruck. Immunob/ologv (Stutfgurt) 165 (1983) 147-160.
1161 Y S Klausner, M. Bodanszky, Synthesis 1974. 549-559.
[17] A. Kling. Di,wrtution, Universitiit Frankfurt 1989.
Permethyl-fi-cyclodextrin, Chemically Bonded
to Polysiloxane: a Chiral Stationary Phase
with Wider Application Range for Enantiomer
Separation by Capillary Gas Chromatography **
By Peter Fischer,* Reiner Aichholz, Uwe Biilz,
Markus Juza and Sigfried Krimmer
Dedicated to Professor Franz Effenberger on the occasion of
his 60th birthday
The use of 0-derivatized cyclodextrins as chiral stationary
phases in capillary gas chromatography has attracted increasing interest in recent years.[’ - 31 So far, capillary
columns have been described which are statically coated with
differently derivatized cyclodextrinsl” 31 (these are also commercially available), as well as columns where a physical
mixture of polysiloxane and cyclodextrin is employed as stationary phase (e.g. OV-1701 with 10% permethyl-S-cyclodextrin [’I). Some spectacular GLC enantiomer separations have been achieved with these phases; unfortunately,
individual separation problems frequently require a specially
tailored derivatization of the cyclodextrins (e.g. tripentyl-,
dipentyl/acetyl- etc.).[jl Pure cyclodextrin phases present the
additional disadvantage that the inevitably polar chiral selector is also used for building the phase backbone, which
thence obtains an unnecessarily polar character.
We have attempted, therefore, to utilize the building principle of chiral amide phases, such as Chirasil-~aI,[~~
also for
cyclodextrin phases, and to likewise chemically bond this
chiral selector to a polysiloxane backbone. Thus, more generally applicable, perhaps even thermally and chemically
p] Pnv.-Doz. Dr. P. Fischer, DiplLIng.
[l] J. Montreuil in A. Neuberger, L. L. van Deenen (Eds.): Comprehensive
Biochemistrv. V o l f 9 BII, Elsevier, Amsterdam 1989, p. 1 - 189.
[2] a ) S. Hakomori, Annu. Rev. Immunol. 2 (1984) 103-126; b) P. Vaith, G.
Uhlenhruck, 2. Immuni/ats/orsch. 154 (1978) 1 - 14.
[3] a ) G . F. Springer, Bull. Inst. Pusteur (Purls) 81 (1983) 127-158; b ) G . F.
Springer, S. Murthy. P. R. Desai, W. A. Fry, H. Tegtmeyer, E. F. Scanlon,
Klin. Wochenschr.60 (1982) 121 -131
Anxew. C h f m In!. Ed. En$ 29 (1990) No. 4
R. Aichholz, DipLChem. U. BOIz.
M. Jura, DipLChem. S. Krimmer
Institut fur Organische Chemie der Universitiit
Pfaffenwaldring 55, D-7000 Stuttgart 80 (FRG)
[**I Chiral Recognition in Capillary Gas Chromatography, Part 3. For generous support of this work, we are indebted to Carlo Erba Instruments.
D-6238 Hofheim (FRG). - Part 2 : R Aichholz, U. Bolz. P. Fischer, HRC
CC J High Resolut. Chromurogr. Chromulogr. Commun. 13 (1990). in
;c> VCH Verlug.~ge.sPllschufimbH, D-6940 Weinheim, 1990
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iodosuccinimide, synthesis, disaccharides, galactal, glycopeptides, faciles, use, linked, activated, gal
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