benzyl (3R,4R)-3-(N-(tert-butoxycarbonyl)-N-(5-tosyl-5H-pyrrolo[2,3-b]pyrazin-2-yl)glycyl)-4-ethylpyrrolidine-1-carboxylate and benzyl (3S,4S)-3-(N-(tert-butoxycarbonyl)-N-(5-tosyl-5H-pyrrolo[2,3-b]pyrazin-2-yl)glycyl)-4-ethylpyrrolidine-1-carboxylate