Synthesis and reactivity of alpha-trialkylsilyl alpha-amino acids
type: CreativeWork
description: This work deals with the synthesis and reactivity of alpha-trialkylsilyl alpha-amino acids. They were synthesised using an established protocol involving rhodium(II)-catalysed insertion reactions of alpha-trialkylsilyl alpha-diazo esters into N-H bonds of carbamates. As an extension to this procedure, it was accounted that a diastereoselective approach to N-protected alpha-trialkylsilyl alpha-amino acids precursors may lead, after deprotection, to the formation of enantiomerically-pure alpha-trialkylsilyl alpha-amino acids. A variety of diastereoselective synthetic strategies were examinated. These investigations involved the use of alpha-trialkylsilyl alpha-keto-acetates as substrates, as well as various reactants such as chiral amines, ureas, or carbamates as sources of the chiral information. Carbamates were confirmed as the mostly efficient N-H sources for rhodium(II)-catalysed reaction. A diastereoselective N-H insertion reaction was attempted between a alpha-triethylsilyl alpha-diazo benzyl acetate and L-menthyl carbamate. The reaction proceeded in a diastereoselective formation of the N-H inserted product in a diastereomeric ratio of 75 to 25. A part of this project was then devoted to the synthesis of the racemic N-Cbz-protected 2-trimethylsilyl glycine. The possibility to obtain the free carboxylic functional group of the named compound from selective deprotection of a corresponding ester moiety was investigated. Various ester protecting groups were considered, the removal of which could give access to the free carboxylic acids and thus to enantiopure alpha-silyl alpha-amino acids through resolution by chemical methods. The most promising result was obtained when the 2-triethylsilyl-2-diazo-(4-methoxybenzyl) acetate underwent reaction with aluminum thrichloride/ethanthiol to yield to the mono-deprotected compound in a 1H NMR ratio 1.6 to 1 respect to the substrate. Attempts to selective removal of the benzyl ester moiety of N-Cbz-protected alpha-silyl alpha…
abstract: This work deals with the synthesis and reactivity of alpha-trialkylsilyl alpha-amino acids. They were synthesised using an established protocol involving rhodium(II)-catalysed insertion reactions of alpha-trialkylsilyl alpha-diazo esters into N-H bonds of carbamates. As an extension to this procedure, it was accounted that a diastereoselective approach to N-protected alpha-trialkylsilyl alpha-amino acids precursors may lead, after deprotection, to the formation of enantiomerically-pure alpha-trialkylsilyl alpha-amino acids. A variety of diastereoselective synthetic strategies were examinated. These investigations involved the use of alpha-trialkylsilyl alpha-keto-acetates as substrates, as well as various reactants such as chiral amines, ureas, or carbamates as sources of the chiral information. Carbamates were confirmed as the mostly efficient N-H sources for rhodium(II)-catalysed reaction. A diastereoselective N-H insertion reaction was attempted between a alpha-triethylsilyl alpha-diazo benzyl acetate and L-menthyl carbamate. The reaction proceeded in a diastereoselective formation of the N-H inserted product in a diastereomeric ratio of 75 to 25. A part of this project was then devoted to the synthesis of the racemic N-Cbz-protected 2-trimethylsilyl glycine. The possibility to obtain the free carboxylic functional group of the named compound from selective deprotection of a corresponding ester moiety was investigated. Various ester protecting groups were considered, the removal of which could give access to the free carboxylic acids and thus to enantiopure alpha-silyl alpha-amino acids through resolution by chemical methods. The most promising result was obtained when the 2-triethylsilyl-2-diazo-(4-methoxybenzyl) acetate underwent reaction with aluminum thrichloride/ethanthiol to yield to the mono-deprotected compound in a 1H NMR ratio 1.6 to 1 respect to the substrate. Attempts to selective removal of the benzyl ester moiety of N-Cbz-protected alpha-silyl alpha…
author: Veri, Elisabetta
language: eng
keywords: info:eu-repo/classification/ddc/540, Chemie, Aminosäuren, Carbene, Rhodium-katalyse, NH Insertion, Amino Acids, Rhodium-catalysis
date published: 2006
date modified: 2026-07-30T19:43:10Z
provider: RWTH Aachen University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Publikationsserver der RWTH Aachen University