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The structure and absolute configuration of the novel tetracyclic diterpenoid aphidicolin, an antimitotic and antiviral metabolite of Cephalosporiurn aphidicola Petch, have been determined, and a systematic nomenclature is proposed. Possible biosynthetic routes to aphidicalin are discussed. Derivatives of aphidicolin, including possible biogenetic precursors and the C(3)and C(16)-epimers of the antibiotic have been prepared. The high resolution i.r. hydroxyfrequencies are reported for a number of ring-A 1.3-diols derived from aphidicolin. 2 R. A. Bucknall, personal communication. consistent with structures (1) or (22) for aphidicolin but is not readily accommodated by structure (23).Baeyer-Villiger oxidation of the ketone (5) gave the lactone (26) which was converted into the acetonide

BN1 9Q J) Summavy (M~,S~CH,CU)~ consists of discrete, centrosymmetric, tetrameric units containing a square plane of copper atoms (Cu-Cu 2-42 A), with the methylene carbons lying in the same plane and bridging the edges.NO crystal structures have yet been reported of copper alkyls although X-ray analyses of copper(1) arylsl have revealed tetra-or hexa-meric copper clusters with aryl groups bridging the edges. We have now determined the structure of the dl0 complex, tetrakis[trimethylsilylmethy1copper(^)],^ that is found to contain an unusual square planar arrangement of copper atoms.

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The determination of the structure of a reaction intermediate gives strong evidence for an unusual mechanism of insertion of an acetylene into the methylgold bond.