73805-83-1 NSC 221291 O,O'-Dibenzyl-4-mercapto-2-phosphonaminobutyric acid lactone Phosphonic acid, (2-oxo-3-tetrahydrothienyl)-, dibenzyl ester Phosphoramidic acid, (tetrahydro-2-oxo-3-thienyl)-, bis(phenylmethyl) ester (9CI)