Stereoselective Synthesis of γ‐Fluorinated α‐Amino Acids Using 2‐Hydroxy‐3‐pinanone as an Auxiliary

doi:10.1002/1099-0690(200011)2000:22<3737::AID-EJOC3737>3.0.CO;2-A

Paper

Stereoselective Synthesis of γ‐Fluorinated α‐Amino Acids Using 2‐Hydroxy‐3‐pinanone as an Auxiliary

Published Nov 1, 2000 · K. Laue, S. Kröger, E. Wegelius

European Journal of Organic Chemistry

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19

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Abstract

(+)-(S)-2-Amino-4-fluorobutanoic acid (5a) (> 96% ee), its α-methylated derivative (+)-(S)-5b (85% ee), and (−)-(S)-2-amino-4-fluoro-4-pentenoic acid (10) (81% ee) were synthesized by diastereoselective alkylation in the presence of LDA at low temperatures. Alkylation of (+)-(R,R,R)-2-hydroxy-3-pinanone based imines of glycine tert-butyl ester 1a or alanine isopropyl ester 1b with 1-bromo-2-fluoroethane (2) or 3-bromo-2-fluoropropene (7), respectively, followed by stepwise deprotection was used. The selectivity of the alkylation increased by lithium/magnesium exchange or for 1b also by addition of DMPU. Differences in the reactivity of enolate alkylations of enantiomerically pure or racemic Schiff base 1a with 2 or 7, respectively, can be explained by the formation of structurally different aggregates of the enolates in solution, caused by diastereomeric interactions between enantiomers in the transition state of alkylation.

Study Snapshot

Stereoselective synthesis of -fluorinated amino acids using 2-hydroxy-3-pinanone as an auxiliary agent enables the production of -fluorobutanoic acid, its -methylated derivative, and ()-(S)-2-a

PopulationOlder adults (50-71 years)

Sample size24

MethodsObservational

OutcomesBody Mass Index projections

ResultsSocial networks mitigate obesity in older groups.

Stereoselective Synthesis of γ‐Fluorinated α‐Amino Acids Using 2‐Hydroxy‐3‐pinanone as an Auxiliary

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