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Synthesis and Decomposition of Organic Peroxides.

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At desaspidine concentrations of 10-7 M the cyclic and the
non-cyclic phosphorylation (measured by the formation of
ATP) and the electron transport (measured by 02-production)
are unchanged. With 10-6 M desaspidine, cyclic phosphorylation is blocked, and only at 2 x 10-5 M non-cyclic
phosphorylation as well. The 02-production, i.e. the electron
transport, is not blocked at desaspidine concentrations below
2xlO-4M. The absorption changes of the participants of
electron transport such as Chl-at, Cyt-f, Cyt-b, and PQ
show the same dependence on the concentration of desaspidine as the 02-production. However, the reaction of Chl-b
parallels the behavior of the non-cyclic phosphorylation
(Fig. 1). Addition of ethanol also blocks phosphorylation
without interrupting the electron transport 151.
From the position of the absorption changes of chlorophyll-b
it can he supposed that a dissociation of H+-ions[sl from
chlorophyll-b takes place. Obviously phosphorylation and
this dissociation (pH-change) are related to each other.
Received: April 12th, 1966
[Z 202 IE]
German version: Angew. Chem. 78, 550 (1966)
[ I ] H . T . Witt, B. Rumberg, P. Schmidt-Mende, U . Siggel,
B. Skerra, J. Vater, and J . Weikard, Angew. Chem. 77, 821
(1965); Angew. Chem. internat. Edit. 4, 799 (1965).
121 Z.Grornet-Elhananand D.I.Arnon, PlantPhysiol.40, 1060( 1965).
[ 3 ] B. Rumberg, P . Schmidt-Mende, B. Skerra, J . Vater, J . Weikard, and H . T . Witt, Z . Naturforsch. ZOb, 1085 (1965).
[4] H . Baltscheffsky and D . Y . de Kiewiet, Acta chem. scand. 18,
24G5 (1964).
[5] H . Baltschqffsky, Acta chem. scand. 17, 308 (1963).
[6] M . Avron, Biochim. biophysica Acta 40,257 (1960).
[7] B. Rumberg, Biochim. biophysica Acta 102, 354 (1965).
[8] A. Weller, J. Amer. chem. SOC.76, 5819 (1954).
CONFERENCE R E P 0 RTS
Recent Results of Antibiotics Research
Ch. Tnmm, Base1 (Switzerland)
T o date, 14 antibiotics termed verrucarines and roridines [ I ]
have been isolated from Myrothecium verrucaria and M .
roridum. The principal products are antifungal and, in particular, potent cytostatic agents; however, they are also very
toxic
Verrucarine E, one of the minor N-containing metabolites, has
been assigned the structure of the hitherto unknown 4-acetyl2-hydroxymethylpyrrole (I). On basic hydrolysis, verrucarines A, B, J, and H, and roridines A , D, and E, yield the
same sesquiterpene alcohol, verrucarol (C15H2204), but they
differ in the products of acidic hydrolysis. Verrucarine A
(C27H3409) gives cis,trans-muconic acid and verrucarinolactone (C6H1003), verrucarine B (C27H3209) gives cis,transmuconic acid and 2,3-epoxy-3-methyl-5-valerolactone
(CsH802); verrucarine J (C27H3208) gives cis,trans-muconic
acid and the known 3-methyl-2-pentenolactone (anhydromevalolactone) (C6HsO) ; roridine A (C29H4009) gives
roridinic acid (C14H2207), roridine D (C29H3808) gives anhydroepoxyroridinic acid (C14H2007) ; roridine E (C29H3808)
gives anhydrororidinic acid (C14H2006); and verrucarine H
(C29H3608) gives 3-methyl-2-pentenolactone and myrothecinic acid (CsHloOs). The structures and stereochemistry of
the new lactones and dicarboxylic acids have been elucidated.
The constitutions of verrucarol (2) and roridine C (= trichodermol) (3) were derived by correlation with trichothecolone
and trichodermine [21.
(4)
degradation experiments showed that the radioactivity of the
verrucarinic acid was derived from C-2 of mevalonate.
[Lectures given at Freiburg, Gottingen, and Marburg
(Germany), on December 3rd, 1965, and January 20th and
21st, 19461
[VB 9831290 IE]
German version: Angew. Chem. 78, 496 (1966)
[ l ] E. Harri el al., Helv. chim. Acta 45, 839 (1962); B. Bohner ef
a/., ibid. 48, 1079 (1965).
[2] J . Gutzwiller et al., Helv. chim. Acta 47, 2234 (1964); J.
Gutzwiller, Ch. Tamm, and H . P. Sigg, Tetrahedron Letters
1965,4495.
131 J. GutzwiNer and Ch. Tamm. Helv. chim. Acta 48, 157, 177
(1965); W. Ziircher, J . Gutzwiller, and Ch. Tamm, ibid. 48, 840
(1965); E. Fetz, B. Bohner, and Ch. Tamm, ibid. 48, 1669 (1965).
Synthesis and Decomposition of Organic Peroxides
A . Rieche, Berlin (Germany)
( 1)
(2) R = OH:
(3)R = H
Numerous rearrangements were observed with verrucarol
and trichothecolone, some of which were discussed in detail.
Oxidative degradations and partial hydrolyses showed that
the above hydrolysis products are linked in the original antibiotics in the form of macrocyclic di- and tri-estersc31. For
instance, formulae (4) and (5) were derived for the two
principal metabolites verrucarine A and roridine A, respectively. These many-membered cyclic esters present a new
structural type.
Experiments on the biosynthesis of verrucarine A and roridine A with [2-14C]mevalonate show that mevalonate is a
biogenetic precursor of verrucarol and verrucarinic acid;
Angew. Chem. internat. Edit.
1 Vol. 5
(1966) J No. 5
According to the “RH scheme”rl1 of oxygen attack on
organic compounds, the first products to be isolated are
alkyl hydroperoxides, in accordance with reaction (a). The
radicals initiating the chain reaction are formed, according
to Dulog, by dehydrogenation [reaction (b)]. The hydroperoxides act autocatalytically by partial decomposition into radicals [reactions (c) and (d)].
RHf02
+ ROOH
(a)
RH+02
ROOH
+ R*+.OOH
(b)
+ RO.+.OH
2 ROOH
+ RO*+ ROO.+ HzO
(c)
(d)
Decomposition of hydroperoxides and peroxidation are
reactions of the same order: at very low concentrations they
are usually of the first order, at higher concentrations of the
second order (owing to dimerization). In ethers, hydroperoxides decompose at all concentrations by a reaction of the
first order; here adducts ROOH.R’OR” are present.
523
On peroxidation of unsaturated compounds, several isomeric alkyl hydroperoxides may arise, according to the
number of double bonds. The cause of this is the mesomerism
of allyl radicals formed by reaction (b), e.g. from methyl
3-butenoate ( I ) and crotonate (2).
The so-called halogen-induced oxidation, hitherto incorrectly interpreted, has been clarified. @-Bromo hydroperoxides are obtained from olefins, HBr, and oxygen [41.
[Lectures at Magdeburg and Berlin (Germany),
January 6th and January 21st, 19661
[VB 987j293 IE]
German version: Angew. Chem. 78, 496 (1966)
Although the butenoate ( 1 ) is more easily oxidized, the
hydroperoxide derived from (3) is the main product obtained
from the two esters. The formation of isomeric alkyl hydroperoxides makes it difficult to study the aerial oxidation of
natural unsaturated oils and rubbers, so experiments to this
end have been carried out with unsaturated model substances 121. We were able to synthesize allyl hydroperoxide [31;
it proved to be surprisingly stable.
[l] A . Rieche, Angew.Chem.50, 520 (1937); A.Rieche, E.Schmitz,
and M . Schulz, Z. Chem. 3, 443 (1963).
121 A . Rieche, M . Schulz, H.-E. Seyfarth, and G . Gottschalk,
Fette, Seifen, Anstrichmittel 64, 198 (1962).
[3] H.-E. Seyfarth, J . Henkel, and A . Rieche, Angew. Chem. 77,
1078 (1965); Angew. Chem. internat. Edit. 4, 1074 (1965).
[4] A . Rieche, M . Schulz, and K . Kirschke, Angew. Chem. 77,219
(1965); Angew. Chem. internat. Edit. 4, 244 (1965).
Modern Methods for Electrical Indication of
Titrations
G . Kruft, Frankfurt/Main (Germany)
Ozonolysis of olefins in the presence of amines afforded
I
geminal hydroperoxyamines RHN-C-OOH
I
(by way of the
zwitterion >C+-OO-), which are also obtained from Schiff
bases and H202; they are precursors of 2-alkyloxaziridines.
On treatment with ammonia and ozone, olefins give isooximes (3-substituted oxaziridines) (“ammozonization”).
Cyclohexanone isooxime was isolated as its N-benzoyl
derivative ( 4 ) , which is also formed on ozonization of bi(cyclohexylidene) in the presence of benzamide.
Peroxidation of nitrogen compounds occurs at the carbon
atom next to the nitrogen atom. Tetrahydroisoquinoline and
azepine give peroxides ROOR directly, by way of hydroperoxides ROOH. Hydrazones and hexanolactam give
hydroperoxides ; pyrrolidone gives H202 and succinimide.
Cyclic peroxides such as ( 5 ) and (6) are obtained from pdiketones and “triacetylmethane” by means of H202. Like
acetals, compounds of type (5) readily undergo exchange of
OH groups for OOH or OOR by way of cations stablized by
mesomerism. The symmetrical peroxide (6) has a high
melting point and is chemically unusually stable, although
explosive.
Preparative use of peroxides has received new impulses by
the discovery of “fragmentable” peroxides. Polar cleavage
and synchronous electron shifts lead, by reaction (e), to only
a few fragments, whereas radical decomposition of peroxides
yields a large number of products.
This method leads, for instance, to quantitative cleavage of
2,3,4,6-acetylated t-butyl glucosyl peroxide into arabinose,
formic acid, and t-butyl alcohol (a new method of sugar
degradation).
524
Of the modern procedures for electrical determination of
endpoint those involving noble-metal electrodes polarized
by a few pA of direct current were discussed. These electrodes
differ from the potentiometric ones (which respond to chemical events occurring during the titration without drawing
current) in that their potential is determined only by their
state of polarization, although this in thurn is a fuction
of chemical events during the titration. Against this loss in
specificity is to be set the advantage that polarized indicator
electrodes are universally applicable - for redox titrations as
well as for argentometric, complexometric, and even acidimetric titrations.
Platinum foil electrodes 10 to 100 mm2 in size and polarized
with currents between about 0.3 and 3 FA or potentials up to
several hundred mV have proved valuable. Au, Ag, and
Au-amalgam electrodes can also be used successfully. If
polarization is effected with a constant current, the indication
is described as voltametric, if with constant polarization
potential as arnperometric (or as dead-stop technique if only
small polarization potentials are applied).
Details were discussed for the less well-known voltametry.
The following two forms of indication technique are differentiated : A) Both electrodes are polarized and function
simultaneously for potential measurement. B) Only one of
the two polarized electrodes is a measuring electrode; it
operates in conjunction with an additional, unpolarized
electrode, such as a calomel electrode, also placed in the
solution to be analysed.
For electrochemically reversible titration reactions the technique A gives a titration curve (potential/volume curve)
characterized by a sharp peak; for irreversible systems it
gives a steeply rising curve that somewhat resembles a potentiometric curve in appearance. The maximum or point of
inflection corresponds to the equivalence point.
Independently of the reversibility of the chemical process,
technique B leads to a steeply rising potential-volume curve;
the point of inflection does not correspond exactly to the
equivalence point. The deviation may be positive or negative
according to whether the indication process occurs at the
anode or the cathode, and increases with increasing dilution
of the solution being analysed. This technique is thus useful
for studying electrode reactions rather than for determination
of endpoints.
Independently of which technique is used, voltametric indication involves a connection between polarization current density at the electrodes and concentration of the sohtion being analysed. Conditions are optimum at a polarization current density of about 0.05-0.1 pAjmm2 in titration
with 0.1 N solutions, or about 0.02-0.05 pA/mm2 or 0.005
to 0.02 pA/mmZ for titration with 0.01 N or 0.001 N solutions, respectively.
Angew. Chem. internat. Edit.
Yol. 5 (1966)
No. 5
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