4-Thia-1-azabicyclo(3.2.0)heptane-2-carboxylic acid, 6-(((((2-(4-formyl-1-piperazinyl)-1,5-dihydro-5-oxopyrido(2,3-d)pyrimidin-6-yl)carbonyl)amino)(4-hydroxyphenyl)acetyl)amino)-3,3-dimethyl-7-oxo-, (2S-(2alpha,5alpha,6beta))-