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Ergot Pigments.

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manno-pentahydroxypentyll-1,5-diphenylverdazyls, and 3[D-nrabo-, 3-[~-rhamno- and 3-[~-xylo-tetrahydroxybutyl]I ,5-diphenylverdazyls. Free radicals of this type affect the
decomposition of H202 by catalase.
Combination of two 3-verdazylyl residues by a 1,3- or 1,4phenylene bridge (F. A . Neugebauer and H. Trischmann)
gives fully conjugated, planar, green biradicals with properties which correspond to those of the simple verdazyls.
Examples of these compounds are 1,3-bis-[1,5-diphenyl-3verdazylyl]benzene, m. p. 184-1 85 "C (decomp.). magnetic
moment p / p ~= 2.46 (found), hmaxl = 719 m y (E = 8200),
and 1,4-bis-[1,5-diphenyl-3-verdazylyl]benzene( 2 ) , m.p.
190 -192OC (decomp.), Amaxl = 732 m y (c = 7400). The
ESR spectra of these biradicals ( K . H . Hausser and P. Fischer) d o n o t show the 9 lines characteristic of verdazyls;
they indicate interaction between the two unpaired electrons
(also observed with the m-compound). Reversible polarographic oxidation yields the diamagnetic, violet, divalentcation (4) via the violet monoradical cation ( 3 ) , which gives
a typical verdazyl ESR spectrum with 9 lines.
4,4'-bond [2,3]. Three further similar, pale yellow pigments,
which we denote as secalonic acid C, ergochrysin A, and
ergochrysin B, have been isolated as pure crystalline individuals. Their analyses, infrared, ultraviolet, and N M R
spectra, and specific rotations show them to be u n s y m m e t r i c a l dimerization products of (I), (2), and (3).
0 :
Secalonic acid A : 1- 1
Secalonic acid B: 2 - 2
Secalonic acid C: 1 - 2
Ergochrysin A :
E r g o c h r y s i n B:
P 11
P! 1
The anthraquinonecarboxylic acids endocrocin (4) and
clavorubin, isolated in collaboration with T. Reschke [4],
form a second group of ergot pigments. The structure of 3methyl-l,5,6,8-tetrahydroxyanthraquinone-2-carboxylicacid
(5) has now been determined for clavorubin, and confirmed
by synthesis.
OH 0
c H,
German version: Angew. Chem. 76. 691 (1964)
P h = Phenyl
Some nitrogen-containing free radicals, arranged in order of
decreasing dehydrogenating power, are: tetraphenylpyrryl >
N , N-diphenyl- N'-picrylhydrazyl> 1,1,5,5-tetraphenyl- 1,2,4,5tetraazapentenyl, 1,1,5,5-bisbiphenylene-3-azapentadienyl>
1,3,5-triphenylverdazyl, 1,1,5,5-bisbiphenylene-2,3-diazapentadienyl. Each of the nitrogen radicals can abstract a hydrogen atom from the NH-compounds derived from radicals
lower in this series, being thereby converted itself into the
parent NH-compound.
[GDCh-Ortsverband Mainz [(Germany),
June 4th, 19641
[VB 831/157 IE]
(4), R = H
(S), R = OH
Endocrocin is considered to be the biogenetic precursor
both of the 80 natural anthraquinone pigments known so far
and of the 6 pale yellow ergot pigments [5]. In contrast to
the anthraquinone derivatives, however, the ergot pigments
are derived from endocrocin via a n oxidative ring cleavage
(4) --f (6) 3 ( I ) , (2), or ( 3 ) , analogous to the Baeyer-Villiger oxidation. The six dimeric ergot pigments are subsequently formed from ( I ) , (2), and ( 3 ) by phenol oxidation.
[GDCh-Ortsverband Freiburg-Siidbaden (Germany)
June 5th, 19641
[VB 836/159 IE]
German version: Angew. Chem. 76, 864 (1964)
Ergot Pigments
R. Franck, Kiel (Germany) [I].
The ergot pigments secalonic acid A, secalonic acid B, and
ergoflavin are s y m m e t r i c a l dimerization products of the
monomers ( I ) , f2), and (3), respectively, with a 2,2'- or
[I] In collaboration with G. Baumann,
U.Ohnsorge, and I . Zim-
[2] B. Franck, E. M. Gottschalk, U. Ohnsorge, and G. Baumann,
Angew. Chem. 76, 438 (1964); Angew. Chem. internat. Edit. 3,
441 (1964).
[3] J . W . Apsimon, I . A. Corran, N . G. Creasey, K . Y . Sin?, and
W . B. Whalley, Proc. chem. SOC.(London) 1963, 209.
(41 B. Franck and T. Reschke, Chem. Ber. 93, 347 (1960).
[ 5 ] T. A. Geissman in P. Bernfeld: Biogenesis of Natural Compounds. Pergamon Press, New York 1963, p. 589; S. Gatenbeck.
Svensk. kem. Tidskr. 72, 188 (1960).
Iron(II1) siloxane compounds are reported by H. Schmidbaur.
Reaction of anhydrous FeCI3 with three equivalents of
sodium trimethylsiloxide in ether gives tristrimethylsiloxyiron(lll), m.p. 179-181 "C, sublimation at 135-16OoC/I mm,
yield 40 %, in the form of yellow-green, waxy crystals which
are readily soluble in inert organic solvents. Cryoscopic
measurements show that the compound is dimeric i n solution.
Angew. Chem. internat. Edit.
1 Vol. 3 (1964) / No. I I
Reaction either of this compound with 1 equivalent of alkali
trimethylsiloxide or of FeC13 with 4 equivalents of alkali trimethylsiloxide gives good yields of alkali tetrakistrimethylsiloxyferrates(II1). These are yellowish, finely crystalline, and,
with the exception of the Li compound, hardly soluble in organic solvents. They decompose slowly above 200 "C, becoming
brownincolor./Chem.Ber. 97,836(1 964)/-Ko. [Rd948/268 IE]
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