Chiral Discrimination of Some Annelated Xanthine Derivatives by the Dirhodium Method

Abstract

Complete 1 H and 13 C signal assignments and conformation analyses of the title compounds (racemic mixtures) were performed. Most 1 H and 13 C NMR signals were resolved in the presence of the enantiomerically pure dirhodium complex Rh 2 (MTPA) 4 (Rh*) allowing for clear and simple chiral recognition. A detailed interpretation of the signal shifts (∆δ) and dispersions (∆ν) in the diastereomeric complexes suggested that the π-system around the C-4/C-5 bond of the central im- [a] Universität Hannover,

First direct discrimination of chiral phosphorus thionate (P=S) derivatives by multinuclear magnetic resonance spectroscopy in the presence of a chiral dirhodium complex

“…Even multifuntional compounds can be investigated. 8 In this article, we report on a number of representative examples 1-9 (Scheme 1) that Rh* is indeed an excellent auxiliary for chiral P=S compounds. To our best knowledge, this is the first facile and direct spectroscopic method for chiral recognition of this class of compounds avoiding chemical transformation into diastereomeric systems with subsequent NMR observation.…”