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Light-Induced Activation of 7-Dehydrocholesterol.

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28
122:
Fig. I. ORTEP diagram of the structure of Za in the crystal.
The crystal lattice"21 of 2a accomodates two sets of mutually symmetry-independent molecules (A, B). In accord
with the "P('H}-NMR spectrum, the X-ray structure analysis of 2a also indicates an interaction between C11 and
the lone pair of the phosphorus, which favors the thermal
decomposition (CI 1-P distance = 327 pm). The PCl bond,
of ca. 188 pm, is longer than the PCillkylbonds; this is important, since cleavage of this bond is an important prerequisite for the formation of 3a.
Received: September 28, 1981 [Z 74 1Ej
German version: Angew. Chem. 94 (1982) 395
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982. 893-906
CAS Registry numbers:
l a , 79-36-7; l b , 26073-26-7; lc, 76-02-8; Za, 81456-78-2; Zb, 81456-79-3; Zc,
81456-80-6; 3a, 29804-89-5: 3b, 13363-86-5; 4,81456-81-7; cyclohexene, 11083-8: (C H, ) S i PPh2; I7 154-34-6.
[4] W. T. Brady, Tetrahedron 37(1981) 2949.
171 E. Lindner, H. Lesiecki, Z . Naturforsch. 8 3 3 (1978) 849.
1111 J. Firl, W. Runge, Z. Narurforsch. 8 2 9 (1974) 393: Angew. Chem. 85
(1973) 671: Angew. Chem. Int. Ed. Engl. I2 (1973) 668.
[12] Za crystallizes from ether monoclinically: space group P2,/c,
a = 1 1 13.4(6), b = 1345.6(3), c = 1811.0(5) pm, ,9=96.76(3)", Z=8,
pc.,Ic=1.465 g cm-'. Diffractometer measurements at - 1IO"C. The
structure was refined anisotropically to R=0.034 (apart from H) using
direct methods and Difference-Fourier syntheses for 2157 independent
reflections (O= 3-23") with the SHEL-76 program system.
Light-Induced Activation of
7-Dehydrocholesterol
By Karlheinz Schmitt-Rau* and Manfred Wilk
It has long been presumed that autoxidation products of
cholesterol and its derivatives participate in carcinogenesis"'. We have been able to show'" that 7-dehydrocholester01 (7-DHC) and ergosterol can be oxidized to reactive alkylating species which could possibly react as precarcinogens with cell nucleophiles. 7-DHC is present as provitamin D3 in high concentrations in the skin. Should it likewise be activated in this way by irradiation such that it
reacts with a model nucleophile- I-methylimidazole-this
could give an indication of the mechanism of light-induced
carcinogenesis.
[*I Dr.
I
RO
H-0"
R = A c , R' = C,H,,
Lh-CH,
Photoactivated 7-DHC is thus indeed capable of alkylating nucleophiles such as 1-methylimidazole. Black et al.['31
found that 5a,6a-epoxycholesterol, a well-known carcinogen, is formed on UV irradiation of skin preparations. It
appears plausible that irradiation of 7-DHC in uiuo leads
to similar metabolites, which can be effective as "ultimate
carcinogens". Hence, the reaction described here can be
considered as a model reaction for the initiation of lightinduced cancer illnesses.
Received: October 21, 1981 [Z 72 IE]
German version: Angew. Chem. 94 (1982) 373
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982. 846-852
CAS Registry numbers:
1, 81456-85-1 ; 7-DHC 3p-acetate, 1059-86-5; I-methylimidazole, 616-47-7
[I] G. 0. Schenck, K. Gollnick, 0. A. Neumuller, Justus Liebigs Ann. Chem.
603 (1957) 46.
[5] M. Wilk, K. Schmitt, Z . Narurforsch. B 36 (1981) 248.
(61 L. L. Smith, F. D. Hill, J. Chromarogr. 66 (1972) 101.
[7] M. Wilk, K. Schmitt, Org. Magn. Reson. I5 (1981) 329.
1131 H. S. Black, W. B. Lo, Nature 234 (1971) 306.
Unsymmetrical Transfer of Ally1 Groups in the
Reaction of I(q3-C,H,),M1 (M = Pd, Ni) with
Bis(dipheny1phosphino)maleic Anhydride**
By Dieter Fenske* and Petra Stock
Phosphino derivatives of maleic anhydride are able to
form complexes with transition metals in which the metal
has formally more than 18 valence electrons['.31. Compounds of this type have a tendency to undergo subse-
K. Schmitt-Rau
Physiologisch-chemisches lnstitut der Universitat
Koellikerstrasse 2, D-8700 Wiirzburg (Germany)
Prof. Dr. M. Wilk
Institut fur Organische Chemie der Universitat
Sandhofstrasse, D-6000 Frankfurt am Main (Germany)
356
After 120 hours irradiation of the acetate of 7-DHC (or
of 7-DHC itself) and I-methylimidazole in dichloromethane, a I : 1 adduct of the steroid and nucleophile could
be isolated following the purification steps described in ['I.
Elemental analysis revealed the presence of two additional
oxygen atoms in the molecule. The adduct reacts-on a
thin-layer chromatographic plate-with N,N,N',N'-tetramethyl-p-phenylenediamine, giving a blue coloration indicative of formation of a hydroperoxide. On subsequent
treatment with a saturated aqueous solution of Na2S03the
hydroperoxy group is reduced to a hydroxy group. The cisoid-conjugated double bond system of 7-DHC is no
longer present in the product, as indicated by the absence
of a band at 270-280 nm in the UV spectrum. The adduct
was 'H-NMR spectroscopically identical with the product
of the Fenton reaction of 7-DHC''l. According to all the
above data the adduct formed in the photoreaction has the
structure 1. The I3C-NMR spectrum is also consistent with
this proposed structure['].
0 Verlag Chemie GmbH. 6940 Weinheim. 1982
35 7-362 Advertisement
[*I
Prof. Dr. D. Fenske, P. Stock
lnstitut fur Anorganische Chemie der Universitat
Engesserstrasse, D-7500 Karlsruhe (Germany)
[*"I This work was supported by the Deutsche Forschungsgemeinschaft and
by the Fonds der Chemischen Industrie.
OS70-0833/82/0505-0356 $02.50/0
Angew. Chem. Int. Ed. Engl. 21 (1982) No. 5
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dehydrocholesterol, induced, activation, light
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