mixture of (2S,4S)-4-cyclohexyl-1-[[(R)
[(1R)-2-methyl-1-(propanoyloxy)propoxy](4
phenylbutyl)phosphoryl]acetyl]pyrrolidine-2
carboxylic acid and (2S,4S)-4-cyclohexyl-1-[[(S)
[(1S)-2-methyl-1-(propanoyloxy)propoxy](4
phenylbutyl)phosphoryl]acetyl]pyrrolidine-2-carboxylic
acid