5-Thia-1-azabicyclo(4.2.0)oct-2-ene-2-carboxylic acid, 7-(((((5-hydroxy-2-(1-piperazinyl)pyrido(2,3-d)pyrimidin-6-yl)carbonyl)amino)(4-hydroxyphenyl)acetyl)amino)-3-(((1-methyl-1H-tetrazol-5-yl)thio)methyl)-8-oxo-, monosodium salt, (6R-(6-alpha,7-beta(R*)))- 60837-22-1