close

Вход

Забыли?

вход по аккаунту

?

Biochemistry of Phosphatides Containing Vinyl Ethers (Plasmalogens).

код для вставкиСкачать
Biochemistry of Phosphatides Containing Vinyl
Ethers (Plasmalogens)
By Hildegurd Debuch L “1
Plasmalogens [Z-acyl-1-(l-alkenyl) -sn-glycero- 3 -phosphoryl
compounds [**I] occur, usually as choline or 2-aminoethyl
esters, in almost all animal cells and tissues. By mild acid
hydrolysis the aldehyde that is bound like a vinyl ether is
liberated and a corresponding @-lysophosphatide is formed,
whereas o n mild alkaline hydrolysis a lysoplasma~ogenis
obtained. An “ether phosphatide” is obtained o n catalytic
hydrogenation. (Such compounds often occur in small
amounts also in Nature.)
Plasmalogens are, specifically, components of the lipid
mixtures that are obtained from myelin sheaths of nerve fibers
(occurring there almost exclusively as 2-aminoethyl esters)
and from the phosphatide fractions of heart muscle (here
usually cholineplasmalogens). Correspondence in chain
length and degree of hydrogenation can often be found when
studying the =-groups of glycerophosphatides that are always
derived from fatty acids, fatty aldehydes, or fatty alcohols.
In vitro experiments with tissue homogenates or cell fractions
from brain contributed little to the nature of biosynthesis of
plasmalogens, so that in vivo experiments must be carried out
t o clarify such problems. Results to date do not provide unambiguous evidence whether the enoi-ether-like linkage of
the aldehyde in plasmalogens arises through oxidation of an
ether group or through reduction of a n ester linkage; in any
case, “Clabeled aldehydes are not direct precursors of
plasmalogens in the brain in vivo.
Lecture at Hamburg (Germany) o n December 1 5 , 1967
IVB 133 IE]
German version: Angew. Chem. 80, 321 (1968)
[ * ] Prof. Dr. Hildegard Debuch
Physiologisch-Chemisches Institut der Universitlt
5 Koln-Lindenthal, Joseph-Stelzmann-Str. 52 (Germany)
[**I
“sn” denotes “stereospecific numbering”; for nomenclature
see IUPAC Information Bull. 30, 21 (1967).
Fluorides and Perfluoroorgano-substituted
Compounds of 11+ and 13+
By M . Schmeisser [ *I
iodine monofluoride is accessible in good yields as a pale
gray solid of decomposition point 0 ° C by reaction of
iodine with the stoichiometric amount of fluorine, by reduction of iodine trifluoride with iodine in presence of traces of
pyridine, and by metathetical reaction of iodine chloride
with nitrosyl fluoride, in all cases in CC13F at temperatures
from -40 t o -5OOC:
I2+
F2
+ 21F
Izf IF3 CSH%
ICI+NOF
3 IF
+ IF+NOCl
Compounds C S H ~ N . I ( O ~ C Rwhere
),
R = CF3 o r C6F5, are
obtained by the action of iodine on silver salts of the corresponding perfluorocarboxylic acids in pyridine/benzene and
can be considered as further derivatives o f Il+.
Pale yellow, solid iodine trifluoride, decomposition point
-28 “C, is formed on treatment of iodine with a n excess of
fluorine at -45 O C in presence of catalytic amounts of IF3
or pyridine a n d can be stabilized as 1:l adducts with organic
nitrogen bases. The compounds IFzCI, CF3IF2, C6F51F2.
and IFzN03, which can be considered as derivatives of IF3,
are formed o n low-temperature fluorination of ICI, CF31, and
C6F51, or in the case of IF2NO3 by reaction of IFzCl with
chlorine nitrate.
Angew. Chem. internat. Edit. / Vol. 7 (1968) 1 No. 4
The covalently constituted iodine tris(perfluoroacylates) ( 1 1
I(OzCR)3, where R -- CF3, C2F5, C3F7, or C6F5, can be
obtained in almost quantitative yields (a) by oxidation of
iodine with fuming nitric acid i n presence of the corresponding perfluorocarboxylic anhydride, (b) by treatment of iodine
trichloride with silver perfluoroacylates, or (c) in the case of
iodine tris(trifluor0acetate) by the action of peroxotrifluoroacetic acid and trifluoroacetic anhydride o n elemental
iodine; they can be isolated in pure form by fractional
vacuum sublimation:
(a)
I2
(c)
12
+ 6 HNO, + 6 (CF3CO)20
3
2 I(02CCF3)3
+ 6 NO2
+ 6CF3C02H
(CFjC0)20
(b) IC13 + 3 AgOzCCF3
3 I(OzCCF3)3 + 3 AgCl
CCI )F
+ 3 CF3C03H + 3 (CF3C0)20 ---+
2 I(OzCCF3)3 +
-15°C
3 CF3CO2H
When method (c) is used an intermediate, iodyl trifluoroacetate 102(02CCF3), can be isolated in 95 % yield.
Analogously t o the preparation of iodine trisfperfluoroacylates) methods (a) and (c) can be used for preparation,
also in almost quantitative yield, of pentafluorophenyliodine bis(perfluoroacy1ates) C ~ F S I ( O ~ C Rwhere
) ~ , R = CF3,
C2F5, C3F7, or C6F5. Treating these compounds with
NaHC03, leads to formation of dimeric pentafluoroiodosobenzene (C6F510)2, as does hydrolysis of CsFsIF2. This
dimer reacts with perfluorocarboxylic anhydrides in the
reverse reaction, regenerating the corresponding pentafluorophenyIiodine bis(perfluoroacy1ates).
Lecture at FrankfurtiM. (Germany) o n January 11, 1968 [VB 134 IE]
German version: Angew. Chem. 80, 321 (1968)
[*I Prof. Dr. M. Schmeisser
Institut fur Anorganische Chemie und Etektrochemie
der Technischen Hochschule
51 Aachen, Templergraben 55 (Germany)
[I1 M . Schmeisser, k-.Dahmen, and P . Sartori, Chem. Ber. 100,
1633 (1967).
Mechanism of Indirect Nuclear Spin Coupling
By H. Dreeskamp [*I
Scalar “indirect” spin coupling of nuclei of a molecule causes
splitting of N M R signals owing t o interaction of the magnetic
field of the outer shell electrons and the magnetic dipole that
is associated with the nuclear spin. The coupling constants J
and their appropriate signs can be determined by analysis
of the spectrum or by double resonance experiments and
thus can be traced back to the coupling constant of directly
bound C and H atoms. This constant is known to be positive
(with the implication that a positive J denotes decrease in
energy owing t o antiparallel spin) from measurements on
partially oriented molecules.
For tetramethyl derivatives and hydrides of elements of the
fourth main group ’the normalized coupling constants J’
(defined as the constants referred to a gyromagnetic ratio
of i 1) of two nuclei linked by one bond have positive signs
and are, within a good approximation, proportional to the
product of the valence electron densities at the site of the
coupling nuclei. It is thence concluded that the Fermi contact
term makes a preponderant contribution to coupling of
nucleus and electrons.
In a paper concerned with an MO approach t o coupling
constants calculated from peturbation energies and considering only the Fermi contact term, Pople and Sanfry [ ’ ]
predict for J’ a progression from positive values for the C-H
and the C-C bond t o negative values for the C-F and H-F
bond. The analogous constants for Se and T e compounds
confirm this theory, since J’ for Se-C and Te-C is small
309
Документ
Категория
Без категории
Просмотров
0
Размер файла
142 Кб
Теги
plasmalogens, phosphatidyl, containing, ethers, vinyl, biochemistry
1/--страниц
Пожаловаться на содержимое документа