close

Вход

Забыли?

вход по аккаунту

?

Formation Structure and Synthetic Use of Gluco- and Galactopyranoside Acetophenone Acetals with 1 3-Dioxane Rings.

код для вставкиСкачать
of this plane, while the third sulfur lies on the opposite
side. This arrangement is sirniIar to that of the stable conformation[41of 2 and is expected for steric reasons, although NMR data""] indicate that there is no restricted rotation about the phosphorus central-carbon bonds in 1,
etry at the central carbon and which has one unique and
two stereochemically equivalent phosphonium
The P-C (central) bond length (175 pm) in 4 is similar to
that in 1 (176.2 pm) but both are longer than in ylides such
as Ph,P=CH, (166.1 ~ r n ) ' ~and
~ ' Ph,P=C=PPh, (162.4
~m)[~"'.
Received: July 2, 1982 [Z 81 IE]
revised: January 5, 1983
German version: Angew. Chem. 95 (1983) 237
The complete manuscript of this communication appears i n :
Angew. Chem. Suppl. 1983. 27 1-28 I
CAS Registry number:
1 . Bu4N +,84507-40-4.
Fig. 1. Structure of 1 as the n-BunN+ salt, which crystallizes along with one
acetone molecule. Space group P2,, a=1189.4, b = 1933.1, c = 1259.9 pm,
p= 11 1.42", Z = 2 ; 3644 reflections, R=0.070. Most important bond lengths
[pmland angles ["I: PI-Sl, 197.4; P2-S2, 197.2; P3-S3, 198.1; PI-C, 176.7; P2C, 177.4; P3-C, 174.6; PI-C-P2, 116.0; P2-C-P3, 122.0; P2-C-P3, 121.6.
even at temperatures as low as 178 K. Thirdly, as expected
for a mesomerically stabilized compound of this type, the
P-S bond order decreases and the P-C (central) bond order increases in going from the neutral parent compound 2
to the anion 1. This is indeed the case and is reflected by
P-S bond lengths, which are greater in 1 (mean, 197.6 pm)
and by the P-C (central)
than in 2 (mean, 194.4
bond lengths, which are shorter in 1 (mean, 176. 2 pm)
BnOO
k OBn
O B
[I] a) S. 0. Grim, S. A. Sangokoya, 1. J. Colquhoun, W. McFarlane, J . Chem.
SOC.Chem. Commun. 1982, 930; b) S. 0. Grim, P. H. Smith, L. C. Satek,
1. J. Colquhoun, W. McFarlane, Polyhedron I (1982) 137; S. 0. Grim, P.
H. Smith, S. Nittolo, H. L. Ammon, L. C. Satek, S. A. Sangokoya, R. J.
Khanna, I. J. Colquhoun, W. McFarlane, J. R. Holden, unpublished.
[2] K. Issleib, H. P. Abicht, J. Prakt. Chem. 312 (1970) 456.
[3] H. H. Karsch, Chem. Ber. I15 (1982) 818.
[4J I. J. Colquhoun, W. McFarlane, J.-M. Bassett, S . 0. Grim, J. Chem. Soc.
Dalton Trans. 1981. 1645.
[5] a) B. Zimmer-Gasser, D. Neugebauer, U. Schubert, H. H. Karsch, Z. Naturforsch. B 34 (1979) 1267; b) J. C. J. Bart, Angew. Chem. 80 (1968) 697;
Angew. Chem. In(. Ed. Engl. 7 (1968) 730; c) A. T. Vincent, P. 1. Wheatley, J . Chem. Soc. Chem. Commun.1971. 582.
Formation, Structure, and Synthetic Use of
Gluco- and Galactopyranoside Acetophenone Acetals
with 1,3-Dioxane Rings
By Andras Liptak* and Pbter Fugedi
There are only two examples in the literature concerning
the preparation of 4,6-O-a-methylbenzylidene-hexopyranosides[''. In both cases principally one of the diastereorneric acetals was formed, and an equatorial phenyl group
proposed for these derivatives by analogy with the corresponding benzylidene derivatives121.
n
RO
8
5, R = H; 6, R
13, R
Me; 7, R = Bn
= Me:
14, R = Bn
RS CHzOH
Ph
H RO
o G ' C H 3
BnO
BnOO
k OBn
O B
12
Bn = PhCHz
Ro OMe
n
9, R = H; 10, R
than in 2 (mean, 188.3 ~ m ) [ ~The
] . structure bears a striking
resemblance to the structure of the mesomerically-stabilized dication, [((CH3)3P)3C]Z+,
4, which has a planar geomAngew. Chem. Int. Ed. Engl. 22 (1983) No. 3
= Me,
11, R = Bn
Ro O M e
15, R = Me; 16, R = Bn
[*] Dr. A. Liptak, Dr. P. Fiigedi
Institute of Biochemistry, Kossuth L. University
P.O.B. 55, €3-4010 Debrecen (Hungary)
0 Verlag Chemie GmbH, 6940 Weinheim, 1983
0570-0833/83/0303-0255 $02.50/0
255
Reinvestigation of the acetal exchange reaction (dimethylformamide, p-toluenesulfonic acid, room temperature)
between acetophenone dimethyl acetal and glucopyranoside derivatives 1-3 revealed formation of both isomeric
acetals, whereby the products of kinetic control (5-7),
isolable in yields of 20-30%, were readily converted into
the thermodynamically favored isomers 9-11. Under
equilibrium conditions the latter accumulate exclusively
and can be isolated nearly quantitatively. The galactopyranoside derivative 4 reacted similarly to give 8 and 12.
The configurations of the acetal carbons were assigned
from ‘H and I3C chemical shifts of the C-2‘ substituents;
these data are highly diagnostic in 2,2-disubstituted 1,3-dioxanes. For an axial methyl group the ‘H-NMR signals
are observed at lowerI3]and the corresponding I3C-NMR
signals at higher field141
than in the equatorial isomer. In the
present case the products of kinetic control ( 5 - 8 ) (Table
1) surprisingly proved to be the (R)-isomers with axial methyl groups, whereas the products of the thermodynamic
control (9-12) were the (S)-isomers with axial phenyl
groups.
Table 1. Selected data for compounds 5-16.
Compound
5
6
7
a
9
10
11
12
13
14
15
16
[a10 la1
’H-NMR [b]
’)C-NMR [c]
+
1.68 [el
1.72
1.73
1.69
1.43 [el
1.55
1.55
1.65
1.52
20.9 [el
21.8
22.1
22.1
31.8 [el
31.9
32.0
32.3
29 [dl
64
- 57
- 71
209 [d]
154
106
21
192
126
140
33
+
+
+
+
+
+
+
+
+
1.44
1.46
1.43
[a] I n chloroform. [b] C-CH,. in CDCI,, TMS internal standard, 6 values. [c]
C-CH,, in CDCI,. [d] In pyridine, 6 values. [el In [D6]dimethyl sulfoxide.
This result is in marked contrast to earlier conceptions
of carbohydrate acetals of this type, but agrees well with
the finding of Eliel et al.l3]that in a 2-methyl-2-phenyl-l,3dioxane derivative the axial phenyl isomer is more stable
by 2.55 kcal/mol. This can be explained by the fact that in
the “perpendicular” rotamer an axial phenyl group can
avoid unfavorable interactions with other H atoms[31.
Hydrogenolytic ring-cleavage of the diasteromeric a-methylbenzylidene acetals with LiAlH,AIC1316J exhibited a
high degree of regio- and stereoselectivity. The (R)-isomers
gave only the 4-O-(a-methylbenzyl)derivates 13 and 14,
whereas the (S)-isomers afforded the 6-O-(a-methylbenzyl)
derivatives 15 and 16. In both cases only one of the two
possible diastereomeric ethers was formed; the configurations of the new chirality centers are being investigated.
The regioselectivity is reminiscent of the results obtained
in the reduction of the five-membered exo- and endo-benzylidene acetals of carbohydratesi6].
Because compounds 10 and 11 are the only products of
acetalization in equilibrium, and their hydrogenolysis with
LiA1H4-AlCI3 results in 6-ethers, a new route is opened
for the preparation of glucopyranosides selectively unprotected at position 4.
Received: March 18, 1982 [Z 416 IE]
revised: December 28, 1982
German version: Angew. Chem. 95 (1983) 245
The complete version of this communication appears in:
Angew. Chem. Suppl. 1983. 254-263
[I] M. E. Evans, F. W. Parrish, L. Long, Carbohydr. Res. 3 (1967) 453; B. C.
Lipshutz, M. C. Morey, J. Org. Chem. 46 (1981) 2419.
[2] N. Baggett, J. M. Duxbury, A. B. Foster, J. M. Webber, Carbohydr. Res. I
(1965) 22.
131 W. F. Bailey, H. Connon, E. L. Eliel, K. 8. Wiberg, J . Am. Chem. SOC.100
(1978) 2202, and references cited therein.
[4] P. J. Garegg, B. Lindberg, I. Kvarnstrom, Carbohydr. Res. 77 (1979) 71.
161 A. Liptak, P. Fiigedi, P. NBnasi, Carbohydr. Res. 51 (1976) C19, and references cited therein.
BOOK REVIEWS
Properties of Ligands and Solutions. By J. N . Muriel1 and
E. A . Boucher. John Wiley & Sons, Chichester 1982. x,
288 pp., bound, E 8.90.
This book is an excellent introduction to the fundamentals of the science of liquids, its 13 chapters giving a brief
but clear account of virtually all topics of interest to chemists, biologists, physical chemists, and other scientists.
Chapter 1 is a short introduction and Chapter 2 deals
with intermolecular forces. Chapter 3 outlines the modem
theories and models of liquids, including the latest developments in statistical thermodynamics and computer simulations. The thermodynamic properties of pure liquids are
discussed in Chapter 4, and liquid crystals (though rather
briefly) in Chapter 5. The topics dealt with in Chapters 6
and 7 are respectively: mixtures of non-electrolytes, and
the phase behavior of multicomponent systems. Chapter 8
is devoted to polar liquids and Chapter 9 to aqueous elec256
trolyte solutions. The authors discuss chemical equilibria
in solution in Chapter 10 and polymer solutions and their
special characteristics in Chapter 11. Chapter 12 deals with
the problems of liquid boundary layers and adsorption
phenomena and Chapter 13 gives an account of colloidal
systems.
The book is not limited to general and standard cases
but often gives direct applications of particularly interesting systems. For example, Section 8.5 discusses the structural model of water that has emerged from the various investigations. Wherever possible, the statistical and thermodynamic models are explained as far as is necessary for
understanding the principles.
Although the aim of the book is to give an introduction,
which in fact it does, it presupposes some background
knowledge in various areas : from thermodynamics, the basic relationships, from statistical mechanics only the MaxAngew. Chem. Int. Ed. Engl. 22 (1983) No. 3
Документ
Категория
Без категории
Просмотров
0
Размер файла
198 Кб
Теги
synthetic, structure, galactopyranosid, formation, acetals, acetophenone, ring, dioxane, gluck, use
1/--страниц
Пожаловаться на содержимое документа