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Enantioselective syntheses of 2-amino-4-fluoropent-4-enoic acids. Isosteres of asparagine
✍ Scribed by Klaus W. Laue; Christian Mück-Lichtenfeld; Günter Haufe
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- French
- Weight
- 649 KB
- Volume
- 55
- Category
- Article
- ISSN
- 0040-4020
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✦ Synopsis
Diastereoselective alkylation of (R)-(+)-camphor-based glycine or alanine esterimines with 3bromo-2-fluoropropene after hydrolytic deprotection gave (R)-(+)-2-amino-4-fluoropent-4-enoic acid with 38% overall yield and 90% ee, or (R)-(+)-2-amino-4-fluoro-2-methylpent-4-enoic acid (19% overall yield, 59% ee), respectively. Deprotection under drastic conditions was accompanied by hydrolysis of the fluorovinyl moiety to give (R)-(-)-2-aminoM-oxopentanoie acid hydroehloride with 28% overall yield and >95% ee. Ab initio calculations of acetamide and 2-fluoropropene as models for a primary amide or a fluorovinyl group despite of their different electronic structure show a similar electrostatic potential on the van der Waals surface suggesting their isosteric behavior.
📜 SIMILAR VOLUMES
## Abstract All compounds are purified by recrystallization from an aprotic, non‐polar solvent like toluene and hexane.
Olefination of a-silyl-, a-phosphoryland a-stannyl-stabilised phosphonate carbanions derived from cyclo-[L-AP4-D-Val] Li + 4b-d -allow a (Z)-selective access to the a,b-substituted vinylphosphonates 7A-E that have been transformed into enantiomerically pure 4-alkylidene AP4 derivatives 12A,B and 13A