ABSTRACT
The first successful resolution of rac-α-aminoacetals via diastereoisomeric salt formation with optically pure N-protected aminoacids is reported. The absolute configuration assignment of α-aminoacetal enantiomers is performed by an entirely non-racemizing chemical correlation method involving N-protection and a new efficient hydrolysis step followed by a reduction of the resulting N-protected α-aminoaldehyde intermediates. A racemization method of optically enriched α-aminoacetals is exemplified to allow valorisation of both enantiomers.
Subject(s)
Acetals/chemical synthesis , Amines/chemical synthesis , Acetals/chemistry , Acetals/isolation & purification , Acetone/chemistry , Acetonitriles/chemistry , Aldehydes/chemical synthesis , Aldehydes/chemistry , Amines/chemistry , Amines/isolation & purification , Chromatography, High Pressure Liquid , Furans/chemistry , Hydrogenation , Hydrolysis , Oxidation-Reduction , Solvents/chemistry , StereoisomerismABSTRACT
The use of all chromatographic modes (i.e. reversed-phase, normal-phase and polar organic modes) is becoming more and more systematic in chiral HPLC method development. When this method development is monitored by polarimetric detection, which is a widespread technique, one should not forget that the observed positive or negative rotation angle for a given absolute configuration depends on the solvent. As a cautionary illustration, a new example is reported for a racemate which is separated with the same elution order in ethanol or acetonitrile mobile phase on a CHIRALCEL OD-R column whereas the signs of polarimetric detection are reversed.
