The RuO4-catalysed dihydroxylation, ketohydroxylation and mono oxidation--novel oxidation reactions for the synthesis of diols and alpha-hydroxy ketones

Alpha-hydroxy ketones are versatile intermediates for the synthesis of complex molecular architectures and subunits of a variety of natural products. Different approaches towards the synthesis of this important functional group combination have been elaborated. The present article summarises our research on the field of RuO4-catalysed oxidations of alkenes that resulted in the development of the first RuO4-catalysed ketohydroxylation of olefins. Mechanistic investigations of both dihydroxylation and ketohydroxylation led to the discovery of the first regioselective catalytic mono oxidation of vic-diols, which was applied in a two-step sequence of asymmetric dihydroxylation and regioselective mono oxidation to furnish enantiopure alpha-hydroxy ketones with both predictable regioselectivity and absolute configuration.     

On the symbol homomorphism of a certain Frechet algebra of singular integral operators

We prove the surjectivity of the symbol map of the Frechet algebra obtained by completing an algebra of convolution and multiplication operators in the topology generated by all L²-Sobolev norms. The proof is based on an ⁿ of Egorov's theorem valid for non-homogeneous principal symbols, discussed in [5], [6]. We use the hyperbolic equation u/t=i|D|u, 0<<1, which has its characteristic flow constant at infinity, so that no differentiability of the symbol is required there.     

Zur Theorie der Bildung von Gelen

Colloid and Polymer Science -     

Pyrazolo[3,4-d][1,2,3]triazine DNA: synthesis and base pairing of 7-deaza-2,8-diaza-2'-deoxyadenosine

7-deaza-2,8-diaza-2'-deoxyadenosine (4) was synthesized from 8-aza-7-deaza-2'-deoxyadenosine (1) via the 1,N(6)-etheno derivative 5. Ring opening with sodium hydroxide followed by ring closure in the presence of sodium nitrite formed the tricyclic intermediate 5 from which the transiently introduced "etheno" moiety was removed with NBS. Compound 4 was converted to the phosphoramidite 11, which was employed in solid-phase oligonucleotide synthesis. Base pairing studies on 4, incorporated in a 12-mer duplex, showed that this adenine nucleoside analogue forms a strong base pair with dG but not with dT. This novel base pair is as stable as that of the canonical dA-dT pair. As a result of the absence of nitrogen-7 compound 4 is expected to form a face to face base pair with dG.     

Fluorinated Musk Fragrances: The CF2 Group as a Conformational Bias Influencing the Odour of Civetone and (R)‐Muscone

The difluoromethylene (CF₂) group has a strong tendency to adopt corner over edge locations in aliphatic macrocycles. In this study, the CF₂ group has been introduced into musk relevant macrocyclic ketones. Nine civetone and five muscone analogues have been prepared by synthesis for structure and odour comparisons. X‐ray studies indeed show that the CF₂ groups influence ring structure and they give some insight into the preferred ring conformations, triggering a musk odour as determined in a professional perfumery environment. The historical conformational model of Bersuker and co‐workers for musk fragrance generally holds, and structures that become distorted from this consensus, by the particular placement of the CF₂ groups, lose their musk fragrance and become less pleasant.