The X-ray structures of 1,8-bis(trimethylgermyl)naphthalene (4) and 1,8-bis(trimethylstannyl)naphthalene (5) have been determined. The structures of 4 and 5 are critically compared with those of 1,3,6,8-tetra-zerz-butylnaphthalene (1) and 1,8-di-ZérZ-butylnaphthalene (2). It is found that familial traits are shared by all the 1,8-bis(trimethylelement)naphthalenes: in each case a twist of the C1-C9-C8 and C4-C10-C5 planes about the C9-C10 axis imparts near C3 symmetry to the molecule, and the trimethylelement groups in the peri positions are further deflected away from each other and out of the average molecular plane. In each case, the effects of internal strain, brought about by repulsion between the (CH3)3Z groups, are felt most strongly near the peri positions, and it is there that the greatest distortions are localized. In this family of compounds, the skeletal distortion decreases in the order 1 (2) » 4 > 5, i.e., in the inverse order of the covalent radius of Z. The conformations adopted by the (CH3)3Z groups in 4 and 5 are almost the same, but distinctively different from those in 1 (2). Empirical force field calculations yield structures in good agreement with those obtained by X-ray diffraction; these calculations also predict that the conformation of the as yet unknown 1,8-bis(trimethylsilyl)naphthalene (3) resembles 4 and 5 more closely than 1 (2) maps had no peaks greater than ±0.5 and ±1.0 e A-3 for 4 and 5, respectively. Stereoviews of the final structures are given in

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The U.V. photoelectron spectra of a number of push-pull substituted ethylenes with two donor groups and with planar or twisted double bonds have been interpreted by the aid of perturbational arguments, CN D0/2 calculations, and comparison with published spectra of similar compounds. The highest bonding molecular orbital in all cases is of x-type, and its energy is raised with increasing twist about the double bond, whereas the orbital formed by antisymmetric combination of the donor atom pz orbitals is unchanged or lowered by increased twist. Through-bond interaction splits the ' non-bonding ' oxygen orbitals by 0 . 6 4 . 7 eV in 1.1 -diacetyl-2,2-diaminoethylenes, in which the carbonyl groups are €,Z oriented with respect to the C=C double bond. When Z,Z orientation is enforced by ring closure, the splitting is only 0.38 eV, in agreement with calculations. In the 2.2-dithio-analogues, interaction with the C-S bond orbitals leads to a more complex splitting pattern.

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The sponge Teichaxinella morchella from the Gulf of Mexico has been shown to contain solely 3F-hydroxymethyl-A-nor-sterols, of which two are the new 3~-hydroxymethyl-A-nor-patinosterol and 3t-hydroxymethyl-A-nordinosterol, isolated as acetates (1) and (1 2), respectively. The 24R and 24s epimers of both 24-methyl-[(4) and(5)] and 24-ethyl-[ ( 8) and (9)] 3~-acetoxymethyl-A-nor-5a-cholest-22-ene were separated by reverse-phase HPLC while the corresponding saturated compounds were isolated as epimeric pairs. The 360-MHz n.m.r. spectra of the 3-acetoxymethyl-A-nor-sterols are discussed. The sole occurrence of A-nor-sterols and the absence of conventional sterols suggest that they are, all bio-transformation products of dietary precursors. Attention is called to the potential chemo-taxonomic significance of this observation. A-NOR-STEROLShave previously been found in five different sponges from four different locations, namely Axinella verrucosa2 collected in the Bay of Naples, Stylotella agminata and Hornaxinella trachy from outside Palau in the West Carolines, an Axinella S P . ~ [0/948 Received, 20th June, ISSO]