Michael Harre

Efficient and environmentally friendly synthesis of 2-amino-imidazole

Abstract A new and efficient method for the preparation of 2-amino-imidazole 3 was developed. Starting from cheap commodities O -methyl-iso-urea sulphate and 2-aminoacetaldehyde-acetales the desired product is isolated through a very simple work-up in a good yield. This new procedure overcomes several technical and environmental problems of the traditional approaches to this molecule and is therefore very attractive for large-scale preparation.

A mild and efficient dehydrogenation of indolines

Abstract A new mild and efficient dehydrogenation of indolines to indoles has been developed. For the dehydrogenation trichloroisocyanuric acid is used in combination with DBU. After work-up with sodium hydrogen sulfite it was possible to obtain indole in an almost quantitative yield. The new method is also suitable for indolines bearing electron withdrawing or electron donating groups. Under the reaction conditions no ring chlorination was observed.

An efficient method for activation and recycling of trityl resins

A mild and efficient method for activation and recycling of trityl chloride resins has been developed. The recycling is performed under mild reaction conditions utilizing thionyl chloride as chlorinating agent. The method is useful for the recycling of the resin during solid phase peptide and organic synthesis.

The first Lewis acid mediated asymmetric Torgov cyclisation

Abstract The first catalytic enantioselective Torgov cyclisation has been achieved in 72% yield and up to 70% ee by using a chirally modified Ti complex. The new bis-steroidal ligands were found to be clearly superior to BINOL.

Synthesis and evaluation of a new steroidal BINAP type phosphine

Abstract The short and high yielding synthesis of a new cis -configured bissteroidal phosphine 7 is reported. The comparison of these new phosphines as ligands in ruthenium-based hydrogenation catalysts with the previously synthesized diastereomeric trans -configured phosphines 20 shows that the steroid backbone exerts only a minor influence on the enantioselection of the ruthenium catalysts and confirms that the bissteroidal phosphines behave as ‘pseudo’-enantiomers in spite of their diastereomeric nature. Evidence is presented that the mode of catalyst preparation, i.e. catalyst structure, is the crucial reaction parameter which mainly determines the enantiomeric excess of the hydrogenation products.

A new family of substituted steroidal BINOL-type ligands ☆

Abstract The short and high yielding synthesis of a new family of substituted bissteroidal BINOL-type ligands employing the bisketone derivatives R ax - , S ax -3 as the centre point of a ‘chemical modular construction system’ is reported.

EFFICIENT SYNTHESIS OF THE GADOLINIUM COMPLEX OF A NEW C2-SYMMETRIC TETRAMINE

Abstract A short and efficient synthesis of the substituted tetramines 2a and 7 and of the gadolinium complex 1 was developed starting from the Cbz-protected amino alcohol 3 . Key steps of the synthesis are the optimized bleach oxidation of enantiopure alcohols and the bridging of the resulting aldehyde molecules by double reductive amination with ethylenediamine. Interesting biological activity of the amines 2a and 7 was detected.

An Efficient Synthesis of 11β-(4-Aminophenyl)spiro[estr-4-ene-17β,2′(5′H)-furan]-3,5′-dione

Abstract An efficient synthesis has been developed affording 11β-(4-aminophenyl)spiro[estr-4-ene-17β,2′(5′ H )-furan]-3,5′-dione ( 2 ), main metabolite of antiprogestin ( Z )-11β-[4-(dimethylamino)phenyl]-17β-hydroxy-17α-(3-hydroxyprop-1-enyl)estr-4-en-3-one ( 1 ), in an overall yield of 21%.

Highly stereoselective 15-ketoreduction of halogenated carbacyclin-precursors

Abstract The stereoselectivity in the carbonyl-reduction of a series α-halovinyl ketones with various reducing agents was studied

E- or Z-selective Wittig reactions in the synthesis of the carbacyclin iloprost

Abstract Wittig reaction of ketones 3 with 4-car☐ybutyltriphenyl-phosphonium bromide generates the exocylic 5,6 double bond of iloprost ( 1 ) in E/Z ratios between 35:65 and 90:10 depending on substituents and reaction conditions.