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Asymmetric Synthesis of γ-Fluorinated α-Amino Acid Derivatives

✍ Scribed by Deepak M. Shendage; Roland Fröhlich; Klaus Bergander; Günter Haufe

Publisher
John Wiley and Sons
Year
2005
Tongue
English
Weight
190 KB
Volume
2005
Category
Article
ISSN
1434-193X

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✦ Synopsis

Abstract

Asymmetric alkylation of (S)‐Boc‐BMI (1a, BMI = 2‐tert‐butyl‐3‐methylimidazolidin‐4‐one) and its α‐methyl derivative 1b with 2‐fluoroallyl tosylate, subsequent mild acidic deprotection of the products 2a and 2b, and basic hydrolysis of the thus formed N‐methylamides 4a and 4b gave (S)‐2‐amino‐4‐fluoropent‐4‐enoic acid (5a) and (S)‐2‐amino‐4‐fluoro‐2‐methylpent‐4‐enoic acid (5b). Basic hydrolysis of compound 4a was accompanied by partial racemization, which was overcome by applying a new stereoconservative deamidation procedure. The alkylated cis‐configured product 2a formed under kinetic control epimerized on refluxing with 2 n NaOH to give the thermodynamically more stable trans isomer 9. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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## Abstract This account concentrates on our new methodologies for the synthesis of fluorine analogues of amino acids and their derivatives using the Reformatsky‐type reactions of ethyl bromodifluoroacetate and ethyl dibromofluoroacetate with imines promoted by the Wilkinson catalyst. First, we pre