(6S)-6-Methoxy-3-[(5-methyl(1,3,4-thiadiazol-2-ylthio))methyl]-5-oxo-6-(2-phenylacetylamino)-2H,6aH-azetidino[2,1-b]1,3-thiazine-4-carboxylic acid, lithium salt AIDS-085773 AIDS085773 LY133539