Abstract
Ethyl 2,3-diendo-3-aminobicyclo[2.2.2]oct-5-ene-2-carboxylate ((±)-1) was resolved with O,O'-dibenzoyltartaric acid via diastereomeric salt formation. The efficient synthesis of the enantiomers of 2,3-diendo-3-aminobicyclo[2.2.2]oct-5-ene-2-carboxylic acid ((+)-7 and (–)-7), 3-endo-aminobicyclo[2.2.2]oct-5-ene-2-exo-carboxylic acid ((+)-5 and (–)-5), cis- and trans-3-aminobicyclo[2.2.2]octane-2-carboxylic acid ((+)-6, (–)-6, (+)-8 and (–)-8) was achieved via isomerization, hydrogenation and hydrolysis of the corresponding esters (–)-1 and (+)-1. The stereochemistry and relative configurations of the synthesized compounds were determined by NMR spectroscopy (based on the 3J(H,H) coupling constants) and X-ray crystallography.
Highlights
In the past decade, the number of investigations on β-amino acids, in both racemic and optically active forms, has risen exponentially as a consequence of their increasing chemical and biological importance. β-Amino acids and their derivatives possess noteworthy pharmacological effects
If there is a large difference in stability of the resulting diastereomeric salt and the enantiomer remaining in solution, the resolutions may be performed with half an equivalent of resolving agent and the achiral auxiliary material is omitted (DL+R → DR+L)
This report focuses on the resolution of racemic 2,3-diendo-3-aminobicyclo[2.2.2]oct-5-ene-2-carboxylic acid derivatives by diastereomeric salt formation
Summary
The number of investigations on β-amino acids, in both racemic and optically active forms, has risen exponentially as a consequence of their increasing chemical and biological importance. β-Amino acids and their derivatives possess noteworthy pharmacological effects. Resolution via diastereomeric salt formation, for instance, is still useful for the production of enantiomerically pure compounds on a laboratory scale. The role of the achiral acid or base is to form a highly soluble salt with the enantiomer remaining in the solution. If there is a large difference in stability of the resulting diastereomeric salt and the enantiomer remaining in solution, the resolutions may be performed with half an equivalent of resolving agent and the achiral auxiliary material is omitted (DL+R → DR+L). A synthesis of racemic 2,3-diendo-3-aminobicyclo[2.2.2]oct-5-ene-2-carboxylic acid has been published [29], but its C-2 epimer and their enantiomers have not yet been examined. This report focuses on the resolution of racemic 2,3-diendo-3-aminobicyclo[2.2.2]oct-5-ene-2-carboxylic acid derivatives by diastereomeric salt formation
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