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New Sideramins from Molds.

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Investigations of the Chemical Causes of
Biological Irradiation Damage
New Sideramins from Molds
By H. Diekmann[*I
By E. Fahr[*]
Along with known sideramins, other hydroxamic acids have
been found
in mold cultures (Fusarium spp., Penicilfium
spp.) grown with a deficiency of iron, and after their extraction and purification their structures have been elucidated.
Fusigen ( I ) is the iron(Ir1) complex of a basic hydrophilic
trihydroxamic acid, in which three molecules of fusarinin are
joined together in a ring by means of ester groups [2J. Hydrolysis of fusigen under mild conditions gives first an openchain trihydroxamic acid (fusigen B), and then fusarinin and
a dihydroxamic acid (fusigen C) by cleavage of a further
ester group. The instability of the hydroxamic acid grouping
in fusarinin eventually has the result that cis-5-hydroxy-3methyl-tpentenoic acid (2) can be extracted from the
cultures [ 3 J .
Other sideramins that have not yet been isolated contain
rrans-5-hydroxy-3-methyl-2-pentenoicacid (3) and are
related to coprogen. This acid (3) occurs to the extent of
about 10 mg/l in cultures of some molds (Penicillium variabife,
Spicaria spp., Neurosporu crassa, Myrothecium roridum,
Myrothecium verrucaria, Fusarium spp.) and can be prepared
in good yield by isomerization of (2). After purification by
Craig distribution and chromatography o n silica gel (solvent:
chloroform/ethanol/formic acid, 94.5: 5 : 0.5, v/v), the acid
( 3 ) was crystallized as its N,N’-dibenzylethylenediammonium
salt (m.p. 64 “C). UV. IR, and N M R spectra, and also thinlayer chromatography, prove its structure.
The action of UV radiation on nucleic acids and their components involves, in the main, two photochemical reactions:
formation of so-called “reversible irradiation products” and
dimerization of pyrimidine bases to “dimeric pyrimidines”.
We have isolated the reversible irradiation products of
uracil, uridine, and uridylic acids and have proved their
structures to be ( l a - e ) by independent syntheses. By an
analogous route we have proved that the very unstable
reversible radiation products of cytosine, cytidine, and cytidylic acid have structures (2a-c). Their radiation products
(2) pass into ( I ) by deamination in a dark reaction. The
photochemical formation of 5,6-dihydro-6-hydroxycytosine
derivatives (21 in the DNA and their subsequent deamination
to ( I ) are likely to be the cause or the mutations induced by
U V radiation.
(a): R
(b):R
H
Ribosyl
( c ) : R = Ribosyl-2(3’)-phosphate
(d) : R = Ribosyl-5‘-phosphate
( e ) : R = Ribosyl-5’-triphosphate
=
=
By degradation to cyclobutane derivatives we have shown
that structure (4a) applies to the dimeric uracil that is formed
o n UV irradiation in an ice matrix. The trans-dimeric uracil
(5a) was synthesized chemically.
H
H
/H
H\
,>-/7”
c-c
\
H\
/o=c
\
N-R
R-
o=c
\
F-’,
H
I
/-,?-/p+
‘,,
\N -R
N-R/
Rv.N--/-C
“cu.
R’
H3C
H
ATc\
H\
‘b
0
(4)
H
H3C,
,COOH
c=c,
HOCH~H~C/
(a): R
(b): R
R‘ = H
Ribosyl, R ‘ = H
(e): R = R’= CH3
(3)
H
Lecture at Stuttgart (Germany) on February 1, 1968
[VB 144 IEI
German version: Angew. Chem. 80, 569 (1968)
[*] Dr. H. Diekmann
Institut fur Mikrobiologie der Universitat
74 Tubingen, Auf der Morgenstelle (Germany)
111 H. Diekmann, Arch. Mikrobiol. 58, 1 (1967).
[21 H. Diekmann and H . Zahner, European J. Biochem. 3. 213
(1967).
[3] W . Keller-Schierlein, H. Zahner, V . Piinter-Streit, and H. Bar,
Biochem. Z. 341, 378 (1965).
Angew. Chem. internar. Edir. I Yol. 7 (1968) J No. 7
=
=
Also the four possible dimeric dimethyluracils ( 3 c ) - ( 6 c )
have been prepared, as well as other dimers.
When we studied the action of ionizing radiation (radiation
dose ca. 500000 rad/min) o n aqueous degassed solutions of
nucleic acid components we obtained a large number of
radiation products. Pyrimidine components were attacked
mainly by H atoms and/or OH radicals at the C = C double
bond. irradiation of cytosine, cytidine, and cytidylic acid
showed that the mutations caused by ionizing radiations
probably arise owing to the following processes: attack by H
atoms and OH radicals on the C=C bond of the cytosine
55 1
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