The synthesis and properties of a number of very strong iminophosphorane bases up to an extremely high level of steric hindrance are described. They cover a range of ca. 4 pK units in basicity and a range of more than 11 orders of magnitude in their rates of methylation with methyl iodide. Most of the systems are readily prepared in up to molar quantities, conveniently recovered from their salts and are of high chemical and thermal stability. Crystal structures were determined in ~~ order to parametrize a force field, which is utilized in molecular modeling studies offering a rationalization of the observed differences in steric hindrance and basicity. Depending on the degree of steric protection of the basic center, these novel bases are proposed as unprecedented, versatile auxiliary bases in E2 eliminations and in reactions involving deprotonation in the presence of more or less strong electrophiles.

Summary. An oviposition-deterring pheromone (ODP) of the European cherry fruit fly Rhagoletis cerasi L. was isolated from faeces using cellulose and several reverse phase TLC and HPLC procedures. The biological activity was evaluated by means of behavior tests and by electrophysiological recordings from tarsal contact chemoreceptors. The compound was structurally characterized as a N[15(fl-glucopyranosyl)oxy-8-hydroxypalmitoyl]-taurine by spectroscopic means. The configurations of C-8 and C-15 of the fatty acid constituent remain to be established by synthetic work.

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The structures of the papulacandins A, B, C and D, new antibiotics of Papularia sphaerosperma have been established by means of spectral analysis and degradation reactions. Base catalysed hydrolysis of the main product papulacandin B (1) gave two new hydroxylated longchain unsaturated fatty acids 5 and 6 along with a hitherto unknown spirocyclic diglycoside 7. The structure of 7 was determined by further degradation reactions. The positions of attachment of the two fatty acids to the spirocyclic diglycoside 7 through ester-bonds were established by selective base catalysed hydrolysis of 1 and spectral analysis of I and some derivatives and degradation products thereof. The structures of papulacandin A (2), papulacandin C (3) and papulacandin D (4) were determined in an analogous way.

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