Synthesis and Rotational Isomerism of 1-Substituted Methyl (S)-[5-(2-Nitrophenyl)-1H-pyrazole-4-carbonyl]alaninates.

Seven title compounds 12a-g and the (S)-prolinate analogue 13 were prepared in five steps from 2-nitrobenzoic acid (7). Reduction of the nitro group followed by derivatization of the so formed anilines 14 gave the N-alkyl-(15a-c), N-acyl-(16a,b and 19), and N-vinyl derivative 20. NMR spectra of (S)-alanine and (S)-proline derived compounds 12, 13, 14-16, 19, and 20 exhibited two sets of signals corresponding to pairs of conformational diastereomers.

A Four-step Synthesis of Novel (S)-1-(heteroaryl)-1-aminoethanes from (S)-Boc-alanine.

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)ethan-1-amines 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)ethanamines 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.