вход по аккаунту


New Methods for Preparation of Glycosides.

код для вставкиСкачать
Because of t h e restricted ion mobility in t h e membrane
phase, glass as well as solid-state membrane electrodes
have strict limitations in respect t o selectivity (see
Section 2). These limitations d o n o t hold for liquidmembrane electrodes. This advantage, however, has
its price in a relatively short life-time of t h e sensor a n d
a sometimes disturbing contamination of t h e sample
solution by membrane components. At present liquidmembrane electrodes f o r NO;, Ca2+, K+ as well as
[Ca2+ + Mg2+] (water hardness) seem t o b e finding
acceptance in a wide range of analytical applications.
Especially high selectivities are t o be expected f o r
liquid-membrane sensors with certain biologically
active materials (antibiotics) as membrane components. Unfortunately o u r knowledge i n connection
with t h e correlation of t h e structure of organic compounds with their ion specificity is still relatively
poor [56,225].
Extremely high selectivities a r e obtained if an enzymatic degradation of t h e components t o be determined
c a n be used. The enzyme-carrying matrix is sandwiched
between t h e sample solution a n d a sensor which
detects one of t h e degradation products 1 8 3 3 - 2 3 3 1 .
There is no d o u b t t h a t by now only a few possibilities
f o r t h e production of i o n selective sensors have been
pointed out. There is therefore a real h o p e t h a t research in this area will drastically influence analytical
chemistry in t h e widest sense.
This work was supported by the Schweizerischer Nationalfonds zur Forderung der wissenschaftIichen Forschung
(Project No. S188.2).
Received: September 2, 1969
[A 759 IE]
German version: Angew. Chem. 82. 433 (1970)
Translated by Express Translation Service, London
New Methods for Preparation of
Glycosides 111 [**I
By Gunter Wulff, Gerhard Rohle, and Wolfgang Kruger [*I
Dedicated to Professor R. Tschesche on the occasion of his
65th birthday
Reaction of 2,3,4,6-tetra-O-acety1-a-~-g1ucopyranosy1
bromide with the silver salt of 4-hydroxyvaleric acid in benzene
gives the glucosyloxy-acid (2) and the I-0-(glycosyloxyacy1)glucose ( 3 ) as well as the very unstable I-0-acylglucose
(2), R
The new method is extremely simple and mild: one merely
stirs the readily available silver salt and, e.g., 2,3,4,6-tetra-Oacetyl-a-D-glucopyranosyl bromide in dry diethyl ether for 30
min at room temperature or for 4 h at -10 OC; and since no
water is produced there is none to remove. 4-Cholestenol, for
example, gives almost wholly 3,5-cholestadiene by the usual
methods, whereas we obtained the glucoside in 36 % yield.
The reaction is clearly applicable also to alcohols of various
types [51; and other cis-halogenoses, e.g., 2,3,4,6-tetra-Oacetyl-u-D-galactopyranosylbromide and 2,3,4-tri-O-acetylP-D-arabinopyranosyl bromide, react analogously.
The reaction is highly solvent-specific; it occurs best in
diethyl ether. Studies of anion-dependence, of the products,
and of the kinetics are in accord with a trimolecular synchronous mechanism.
(I), R
this reaction. Thus, for instance, we obtained cholesterol
P-D-glucoside in 58 % yield (only 33 % 121 or 43 % [31 by the
Konigs-Knorr method and 45 % by Kochetkov’s methodl41)
and a 65 % yield of tigogenin P-D-glucoside (45-50 % by
the Konigs-Knorr method).
c H3
(3), R =
Silver salts of other 4- and of 5-hydroxyalkanoic acids give
analogous products. Moreover, silver salts of 2-, 3-, and
6-hydroxyalkanoic acids afford corresponding products, but
here the 1-0-acyiglucoses are appreciably more stable.
Thus glucosylation of the alcoholic hydroxyl group of the
hydroxyalkanoic acids occurs to a considerable extent in this
reaction. We have therefore investigated the possibility of
glucosylating added alcohols similarly. We found that, in the
presence of silver salts of 2-, 3-, or 4-hydroxyalkanoic acids,
or of 1,3- or 1,4-dicarboxylic acids, alcohols react with 2,3,4,6tetra-0-acetyl-a-D-glucopyranosyl
bromide in ether to give
good yields of 2,3,4,6-tetra-O-acetyl-~-~-glucosides.
4-hydroxyvalerate proved particularly favorable for use in
Angew. Chem. internat. Edit. / Vol. 9 (1970)1 No. 6
+ AgBr
This reaction occurs to any considerable extent only on the
surface of solid bifunctional anions of specific structure.
Such anions include those of 2-, 3-, and 4-hydroxyalkanoic
acids and of certain dicarboxylic acids in which neighboring
group effects limit the formation of 1-0-acylglycoses in favor
of glycoside formation by way of a trimolecular transition
state. The Konigs-Knorr synthesis in the presence of silver
carbonate probably occurs analogously.
Received: February 26, 1970
[ Z 173 IE]
German version: Angew. Chem. 82, 480 (1970)
Publication delayed at authors' request
[*I Dr. G. Wulff, Dipl.-Chem. G. Rohle, and
Dip1.-Chem. W. Kriiger
Institut fur Organische Chemie und Biochemie
der Universitat
53 Bonn 1, Meckenheimer Allee 168 (Germany)
[**I Glycoside Synthesis, Part 1. - This work was supported
by the Deutsche Forschungsgemeinschaft.
[ l ] Extracts from the Habilitationsschrift by' G. WuZfl, Bonn,
[2] H. Lettre and A . Hagedorn, Hoppe-Seylers Z . physiol.
Chem. 242, 210 (1936).
131 C. Meysfre and K . Miescher, Helv. chim. Acta 27, 231
[4] N . K . Kochetkov, A . J . Khorlin, and A . F. Bochkov, Tetrahedron 23, 693 (1967).
[ 5 ] After conclusion of this work, Professor B . Helferich informed us that he had obtained ethyl @-D-ghcoside from
2,3,4,6-tetra-o-acetyl-or-o-glucopyranosy~bromide and ethanol
in the presence of silver salts of dicarboxylic acids (unpublished
Crystalline x-Radicals Containing Lead Isotropic 207Pb-ESRHyperfine Structure
By Hartinut B. Stegmann, Klaus Schefller, and
Fritz Stocker [*I
Dedicated to Professor Eugen Miiller on the occasion of his
65th birthday
Attempts to prepare solutions of paramagnetic organolead
compounds - in particular by dissociation of hexaaryldiplumbanes "1 - have so far been unsuccessful. We have now
been able to isolate lead-containing radicals as products of
the reaction of 2-amino-4,6-di-tert-butylphenoxyl
( I ) with
diaryllead dihalides. Reaction of the aminoaroxyl ( I ) with,
e.g., di-p-tolyllead dichloride in ethanol affords violet-brown
crystals, m.p. 143-145 "C. Elemental analysis and mass
spectrum suggest structure (2). While solid (Zb) gives an
intense ESR signal exhibiting exchange narrowing, its solution in benzene gives a multicomponent spectrum.
Figure: ESR spectrum of the di-p-tolyllead radical (2b) in benzene at
room temperature.
The central section of the hyperfine structure (HFS) of this
spectrum (see Figure) can be interpreted in terms of magnetic
coupling of the free electron with two pairs of protons and
one 14N nucleus. The less intense components lying on the
left- and right-hand sides can be attributed to further coupling
with a z07Pb nucleus. This isotope (I = 1/2) has a n abundance
of 22.62% in natural lead. The observed spectrum agrees very
well with this figure, as is shown by the successful simulation
(CDC 3300) of a n enlarged spectrum.
The isotopic spectrum is masked by the main spectrum only
in the central region, which corresponds to the 77.38% of
nonmagnetic lead nuclei present; thus if both groups of satellites are taken into consideration, the whole 207Pb HFS can
be observed. Exact measurements show that the distances
between the satellite centers and the center of gravity of the
whole spectrum differ in the upfield and downfield directions.
This asymmetry is attributable to a second order shift such
as has already been detected quantitatively for radicals
containing tin [21.
In agreement with other findings, the ESR spectra show the
new organolead derivatives to be 11,ll-disubstituted 1,3,7,9tetra-tert-butyldibenzo[d,g]- [1,3,6,2]dioxazaplumbocin-5-yls.
The coupling parameters were initially assigned by analogy
with the corresponding tin compounds 121.
ESR data for the radicals (2) (gauss), recorded in benzene at room temperature;
A H = line width.
(a). R
(bj, R
1 1 1 1 1 1
As expected, the substituent R has only a limited effect on
the coupling constants. The exceptional line broadening
(% 0.7 gauss) is probably due either to an unresolved proton
HFS o r to unfavorable relaxation conditions. Since the
spectra remain essentially unchanged between -70 and
+120°C, the line broadening cannot be due to mechanical
movement. The g factors of compounds (2a) and (26) are
remarkably small, owing to interaction of the free electron
and the P b nuclei which has also been determined from the
HFS spectra.
Received: December 16, 1969
[ Z 205 IE]
German version: Angew. Chem. 82, 481 (1970)
Publication delayed at authors' request
[*I Priv.-Doz. Dr. H . B. Stegmann and F. Stocker
Chemisches Institut der Universitat
74 Tiibingen, Wilhelmstrasse 33 (Germany)
Dr. K. Scheffler
Present address: Conseil Europeen pour la Recherche
CH-1211 Geneve-Meyrin (Switzerland)
[ l ] Cf. e.g., E. Muller, F. Gunther, K . Scheffler, and H . Fettel,
Chem. Ber. 91,2888 (1958); G. Bahr and G. Zoche, ibid. 88, 542
(1955); R. Preckei and P . W . Selwood, J. Amer. chem. SOC.62,
2765 (1940); U.Belluco, G. Tagliavini, and P. Favero, Ricerca
sci. Rend. Suppl. A 32, 98 (1962); Chem. Abstr. 57, 13786
121 H . B. Stegmann, K. Schefller, and F. Stocker, Chem. Ber.
103, 1279 (1970).
Preparation of Trieihyl Ortho-3-butynoate and its
Conversion into 5-0x0-3-alkynoate Esters and into
Derivatives of 3,5-Dioxoalkanoate Esters 111 [**I
By Rolf Finding and Ulrich Schmidt [*I
Dedicated to Professor Eugen Miiller on the occasion of his
65th birthday
In triethyl ortho-3-butynoate (4,4,4-triethoxy-l-butyne)( I )
[which we obtained from propargylmagnesium bromide and
tetraethyl orthocarbonate) masking of the carboxyl group
as orthoester protects i t from attack by alkali-metal acetylides
and prevents rearrangement of the acetylenic linkage t o the
a,P-position or to a n allenic unit. The orthoester can thus be
Angew. Chem. internat. Edit.
1 Vol. 9
(1970) f No. 6
Без категории
Размер файла
223 Кб
preparation, glycosides, method, new
Пожаловаться на содержимое документа