Photochemie von Aminoketonen. VII. Eine diastereoselektive Synthese von 3‐Hydroxy‐prolinen

Publisher Website
Google Scholar
Abstract
Photochemistry of Aminoketones. VIII. Diastereoselective Synthesis of 3‐Hydroxy‐prolinesGlycine esters react in two steps (aminoalkylation and N‐acylation) to N‐acyl‐N‐(β‐benzoylethyl)‐glycine ester 3. In less polar solvents these ketonic compounds are n,π*‐excited by 300 nm irradiation. In ether 3* yield mixtures of aminocyclopropanoles 4, hydroxyprolines 5 and products of additions and cleavages. In benzene and cyclohexane/benzene, respectively, the regioselective photocyclization to 5 is favoured. Furthermore this hydroxyproline synthesis has the advantages of high diastereoselectivity yielding the (2,3) E–5 and of high overall‐yields in connection with the one pot method. The influence of solvents and substituents on the regio‐ and diastereoselectivity are explained using a model with stabilization of special conformations of intermediates by dipol‐dipol interactions.