N-[[P(S),2′R]-2′-Deoxy-2′-fluoro-2′-methyl-P-phenyl-5′-uridylyl]-L-alanyl-2-hydroxyacetyl-[P(S),2′R]-2′-deoxy-2′-fluoro-2′-methyl-P-phenyl-5′-uridylyl-L-alanine carboxymethyl ester