1	SVZ	O-[(S)-hydroxy(isopropylamino)phosphoryl]-L-serine	1.000
2	SEN	O-[N,N-dimethylphosphoramidate]-L-serine	0.800
3	SXE	O-{(S)-ethoxy[(1-methylethyl)amino]phosphoryl}-L-serine	0.765