A four-step synthesis of novel (S)-1-(heteroaryl)-1-aminoethanes from (S)-Boc-alanine

Abstract

A series of (S)-1-(pyrimidin-4-yl)-, and regioisomeric (S)-1-(pyrazolo[1,5-a]pyrimidin-7-yl)-, and (S)-1-(pyrazolo[1,5-a]pyrimidin-5-yl)-1-aminoethanes were prepared by cyclisation of (S)- N-Boc-alanine-derived ynone with N,N-1,3-dinucleophiles, such as amidines and α-aminoazoles, followed by acidolytic removal of the Boc group. Stereoselective catalytic hydrogenation of (S)-1-(pyrazolo[1,5-a]pyrimidin-7-yl)-1-aminoethanes lead to saturation of the pyrimidine ring to afford ∼4:1 mixture of diastereomeric 4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidines. The structures of novel compounds were elucidated with NMR spectroscopy.