Browsing by Author "Bathich, Yaser"

Now showing 1 - 1 of 1

Open Access
Synthesis of branched amino polyols and amino hydroxy acids : stereoselective addition of C-nucleophiles to isoxazolines and isoxazolinium salts and assignment of configurations
(2006) Bathich, Yaser; Jäger, Volker (Prof. Dr.)
The main aim of this work was based on the development of synthetic routes to amino alcohols as well as branched a- and b-amino acids starting from achiral and chiral (racemic and optically active) isoxazolines and N-methylisoxazolinium salts. The isoxazolines were treated with variety of Grignard reagents and methyllithium complex as C-nucleophiles. These results were comparable to the findings of analog additions to the "activated" isoxazolines, that is, to isoxazolinium salts. The latter react smoothly with Grignard reagents, as well as with weaker C-nucleophiles such as sodium diethyl malonate or lithium ester enolate. At the same time was observed, that the addition has -partially- good diastereoselectivity under mild reaction conditions, and a good yield of the corresponding substituted isoxazolidines. Isoxazolines and isoxazolinium salts deal as versatile synthetic blocks, which were transformed into structurally very different, but nonetheless, important target compounds. Related was the synthesis of amino alcohols and amino polyols, primarily from isoxazolinium salts. This approach required reductive opening of the N-O bond, and was achieved with almost quantitative yields through catalytic hydrogenation. The synthesis of branched b-amino acids was done through the 1,3-amino alcohols (-polyols), which -as were presented in this work- were accessible with good yields and -particulary- high diastereoselectivity. After the introducution of Boc protecting group at nitrogen, were oxidized to carboxylic acid. In some cases b-amino lactones were obtained instead of b-amino acids.