Strukturelle „Valid“‐ierung: Der Mechanismus des enzymkatalysierten konfigurationserhaltenden Glycosyltransfers gibt Rätsel auf, zumal aussagekräftige 3D‐Strukturen ternärer Inhibitor‐Enzym‐Komplexe fehlen. Durch die Synthese und mehrdimensionale kinetische Analyse von Validoxylaminderivaten wurde die 3D‐Struktur eines ternären Komplexes erhalten (siehe Bild; U=Uridyl), der Einblick in die Geometrie und das Donor‐Akzeptor‐Wechselspiel am Glycosyltransferzentrum gibt.

Structural “valid”‐ation: The mechanism of enzyme‐catalyzed glycosyl transfer with retention of anomeric configuration continues to baffle, a situation compounded by the lack of insightful 3‐D structures of ternary enzyme complexes. Synthesis and multi‐dimensional kinetic analysis of validoxylamine derivatives are used to access the 3‐D structure of a ternary complex (see picture; U=uridyl) providing insight into the geometry and donor–acceptor interplay at the glycosyltransfer site.

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On flash vacuum thermolysis at temperatures between 390 and 585", the epoxyenones 1-9 and the epoxydienes 10-12 undergo various types of reactions involving C-C and/or C-0 bond cleavage in the oxirane ring. Thus, the compounds 1,4-9,11, and 12 were transformed to the divinyl ethers 13,20,21,24,25,29, and 38 by a reversible [I ,5] homosigmatropic H-shift. On thermolysis of the epoxides 1-12, several products formed via carbonyl-ylide intermediates were also isolated. The extent of the formation of ylide products is clearly related to the conjugating ability of the functional groups neighboring the oxirane. Thus, the epoxides 3, 5, and 7-10, bearing a C(3)=C (4) bond, a 5-0x0 function, a 3,4-epoxy or a 3,4-methano group, preferentially underwent reactions via a carbonylylide intermediate. As a further reaction pathway, the epoxides 1-12 undergo cleavage of the C-0 bonds of the oxirane, which, however, is presumably an acid-catalyzed rather than a thermal reaction.