for the following products
4-Oxa-2,6-diazabicyclo[3.2.0]hept-2-ene-6-acetic acid, α-(1-methylethenyl)-3-(4-methylphenyl)-7-oxo-, diphenylmethyl ester, [1r-[1α,5α,6(R*)]]- and [1R-[1a,5a,6(R*)]]-alpha-(1-Methylethenyl)-3-(4-methylphenyl)-7-oxo-4-oxa-2,6-diazabicyclo[3.2.0]hept-2-ene-6-acetic acid diphenylmethyl ester