Amarylla Horvath

Isolation of an isomer of FK-506 from fermentation of Streptomyces tsukubaensis and its chemical synthesis from FK-506

Abstract From the fermentation broth of Streptomyces tsukubaensis 9993 an isomer 2a of the immunosuppressant FK-506 1a was isolated as a minor metabolite. From NMR- and FAB-MS data follows that in 2a the size of the macrocycle is reduced by two carbon atoms due to a shift of the lactone-acyl from 0–26 to 0–24. The compound was synthesized from FK-506 and proved to be identical with the natural product 2a.

Regioselective Carbon–Carbon Bond Formation in the Effector Domain of Ascomycin

Abstract Starting from 33- O -silyl-protected ascomycin or its 23,24-dehydration product, regio- and stereo-selective formal aldol reactions under carbon–carbon bond formation at C-22, C-23, or C-24 are demonstrated. Additionally, with the 22-silyl enol ether ascomycin derivative a rhodium(I)-catalysed shift of the 19,20 double bond into the 19,38 exocyclic position is observed at elevated temperature.

Synthetic modifications of Ascomycin - ii.1 A simple and efficient way to modified iso-Ascomycin derivatives

Abstract A simple and convenient semisynthetic preparation of C-26 substituted iso -ascomycin derivatives, starting from the readily available 33-O-silylated 22( S )-dihydro- iso -ascomycin 1 is described.

Formation of tetrahydropyridines from arylnitriles with 2- and 1-propenyl-metals

Abstract Reaction of 4-chlorobenzonitrile or benzonitrile with 2-propenylgrignard or -lithium or with 1-propenyllithium yielded tetrahydropyridines 1 and 8 .