4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylicacid,6-[[[3-(2,6-dichlorophenyl)-5-methyl-4-isoxazolyl]carbonyl]amino]-3,3-dimethyl-7-oxo-,2-(diethylamino)ethyl ester, [2S-(2a,5a,6b)]-