The synthesis of glycopyranosyl nucleosides modified in the sugar moiety has been less frequently explored, notably because of the lack of a reliable method to glycosylate pyrimidine bases. Herein we report a solution in the context of the synthesis of peptidonucleosides. They were obtained after glycosylation of different pyrimidine nucleobases with glucopyranosyl donors carrying an azide group at the C4 position. A methodological study involving different anomeric leaving groups (acetate, phenylsulfoxide and ortho-hexynylbenzoate) showed that a sulfoxide donor in combination with trimethylsilyl triflate as the promoter led to the best yields.

Organofluorine compounds are of high interest in modern drug discovery and material sciences. We herein report a new synthetic access to o-amino-2,2,2-trifluoroacetophenones starting from commercially available o-amino benzoic acids, which can easily be converted into the corresponding benzoxazinones. In a second step the trifluoromethylated ketone is formed via addition of Ruppert’s reagent following acidic work up.

Successful biochemical studies of the natural products belactosin A and C and their acylated congeners have shown a β-lactonecarboxamide moiety to be a possible core structure of powerful proteasome inhibitors. As a part of further investigations, variously decorated simplified β-lactonecarboxamides have been synthesized in order to understand structure-biological activity relations in detail, to find ways of improving their biological activity and stability and to reduce the complexity of their preparation. Biological tests showed that the best compounds possess a high potential against phytopathogenic fungi in the greenhouse.

AbstractA rapid access to 4‐halopyrazole‐3‐boronates (V) proceeds via cycloaddition of sydnones (I) with terminal alkynyl boronate (II) followed by C‐4 halogenation.

The 1,3-dipolar cycloaddition of N-arylsydnones with ethynyl MIDA boronate produces mixtures of the corresponding regioisomeric pyrazolyl 3(4)-boronates, with the pyrazolyl 3-boronates predominating by a factor of 7:3. Further C-4 iodination of the latter opened access to 4-iodopyrazolyl MIDA 3-boronates as valuable scaffolds for the elaboration of unsymmetrically 1,3,4-trisubstituted pyrazole derivatives via Suzuki cross-coupling reactions.

The 1,3-dipolar cycloaddition of diversely N-substituted 4-iodosydnones with 3-halopropiolates produces easily separable mixtures of dihalogenated pyrazolylcarboxylic esters at a preparative scale level, with the 3,5-dihalogenopyrazole regioisomers always predominating. Further decarboxylation of the major isomers provided the corresponding 3,5-dihalogenopyrazoles with a free C-4 position. These were found to be valuable scaffolds for the elaboration of unsymmetrically 1,3,5-trisubstituted pyrazole derivatives by site-selective Pd-catalyzed cross-coupling reactions. Notably, the flexible and site-selective introduction of different (hetero)aryl, vinyl, or alkyl substituents at the C-5 and C-3 positions of the pyrazole core could be achieved through sequential Suzuki-type reactions with various boron compounds. Furthermore, the Suzuki coupling sequence could be amenable to a one-pot procedure that enables rapid generation of the targeted compounds.

AbstractThe methodology, previously developed by Gosh and Zajc, is modified and allows a high diversity of products which are of interest in medicinal chemistry.

AbstractThe introduction of C‐3 and C‐5 substituents at the protected pyrazole ring is possible in a one‐pot reaction with a wide scope of boronic acids.