The consequences of a bridging methylene group in 1, i.e. as in 2, on the geometry and ability to complex Ag(I) were studied. Compound 2 was prepared in three steps and 36% overall yield from 1 in a new procedure and characterized through X-ray crystallography. The X-ray crystal structure of its endo complex (3) with AgC104 shows three independent molecules in the crystal lattice. The geometry of the ligand in 3 is like that in 2. Ag is 2.48-3.00 A from the nearest Ar-C, is 0.13-0.31 A outside of the cavity of 2, and binds nearly symmetrically across the C(5)-C(6), C(ll)-C( 12), and C(23)-C(24) bonds. Compound 2 is shown to be a weaker complexing agent for Ag(I) than [2.2.2]paracyclophane. Practical and theoretical ramifications of the bonding mode are discussed.It is known that small metal cations can combine with aromatic hydrocarbons to form ir-complexes.2>3 This complexation is especially effective for [2.2.2]paracyclophane, 1, and related structures4 that possess x-electronrich cavities. Cyclophane 1 not only forms endohedral complexes with soft metals, but also can form exohedral complexes of varying metal-ligand stoichiometry with chromium(O),5 arsenic(III),6 antimony (III),6 and bismuth-(III).6 In the endohedral complexes of 1, the exact location of the metal atom in relation to the "ir-prismand" cavity depends on its coordination number and the size of the cation: silver(I)4'7 coordinates 3 X ij2 3and is symmetrically bound 0.23-0.24 A outside the cavity, while gallium(I),8 tin(II),9 and germanium(II)9 *complex in the 3 X »/6 mode, well within the cavity.We are interested in modifying the shape and size of the cavity of 1 and related structures and the stability of the resulting metal complexes. From molecular models, it is apparent that the effects of introducing a second bridge between adjacent aromatic rings, as in 2, may involve constricting or expanding the associated side of the cavity,

From the adduct 8, obtained from naphthazarin (6) and the diene 7, the olefin 25 is synthesized via epoxidation (-+15) and treatment with base. Cleavage of the silyl ethers 25 yields the allylic alcohol 26 which can be epoxidized to give 28 and 30 and subsequently cleaved with methanol to yield the methyl ethers 32 and 33. The relative configuration of the acetonide 36 obtained from 33 is confirmed by X-ray analysis; consequently, the relative configuration 1 a of altersolanol A is proved. Furthermore, the mass spectrometrical investigations support the stereochemistry of the isomers 31 -33. The tetracyclic anthracyclinones 40 -42 are synthesized by Diels-Alder reaction of 31, 33, and 36 with l-methoxy-1,3-butadiene. Synthetische Anthracyclinone, XXIXI). -Chinon-Antibiotica mit fiinf Suhstituenten am hydroaromatischen RingDas aus Naphthazarin (6) und dem Dien 7 erhaltliche Addukt 8 wird zu 15 epoxidiert und durch Basenbehandlung zum Olefin 25 umgesetzt. Der durch Spaltung des Silylethers 25 erhaltliche Allylalkohol26 wird zu 28 und 30 epoxidiert und mit Methanol zu den Methylethern 32 und 33 geOffnet. Die relative Konfiguration des aus 33 erhaltlichen Acetonids 36 wird durch Rantgenstrukturanalyse abgesichert; damit ist auch die relative Konfiguration l a des Altersolanols A bewiesen. Ferner bestatigen massenspektrometrische Untersuchungen die Stereochemie der Isomeren 31 -33. Die tetracyclischen Anthracyclinone 40 -42 werden durch Diels-Alder-Reaktion von 31, 33 und 36 mit 1-Methoxy-1,f-butadien erhalten.T h e clinically important antitumor antibiotics of the anthracycline family such as daunorubicin or aclacinomycin A possess three or four substituents at the hydroaromatic part of the molecule with two or three chiral centers, respectively. There are, however, several stereochemically more complex quinoid antibiotics with five substituents at ring A.This group is represented not only by the tetracyclic anthracyclinones aranciamycinonez) (3), 0 VCH Verlagsgesellschaft mbH, D

Model substances for oligomeric systems based on the incorporation of [2.2.2]paracyclophane into the repeating unit are linear polyenes bearing a paracyclophanyl residue in the terrninal positions. The preparation of the polyenes 2a-c is described. In addition to the characterisation as diarylpolyenes, consideration of model compounds revealed that the [2.2.2]paracyclophanyl residues interact with pendent substituents according to a magnetic anisotropic mechanism.The n-electron-rich cavities of [2. The synthesis of butadiene 2b was performed by the Wittig reaction. The phosphonium salt 8 required for one of the two possible synthetic strategies here was obtained in 41% overall yield by bromination of alcohol 5 with phosphorus tribromide followed by treatment of the resulting bromide 7 with triphenylphosphane (Scheme 2). The corresponding reaction partner of 8, the substituted acrylaldehyde 10a, was prepared by two independent sequences: firstly, chain elongation of aldehyde 6 according to the Horner-Emmons with diethylphosphonoacrylonitrile produced the substituted acrylonitrile 9 in 86% yield. The selectivity of this reaction was evaluated by inte-

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Das aus Naphthazarin (I) und dem Dien (II) erhältliche Addukt (IIIa) [Röntgenstrukturanalyse (RSA): P2,2,2,; Z=4] wird über das Epoxid (IV) zum Olefin (VIa) umgesetzt.