A Facile Synthesis of b-Lactams by the Cyclization of b-Amino Acids Exploiting 3,3'-(Phenylphosphoryl)-bis(1,3-thiazolidine-2-thione)

3,3'-(Phenylphosphoryl)-bis(l,3-thiazolidine-2-thione) (5).obtained from phenylphosphonic dichloride (7) and sodium salt of 1.3-thiazolidi~ie-2-thione (6).proved to be useful for inaamolecular dehydration of various p-amino acids to give the corresponding p-lactams.In the formation of amide bond between a carboxylic acid and an amine, various organic phosphorus (V) compounds such as diphenylphosphoryl azide (1),1 bis (0-nitropheny1)phenyl phosphonate (2),2 3,3'bis(2-0x0-3-oxazolidiny1)-phosphomamidic chloride (3)? and diphenyl-2hxo-3-oxawlidinyl phosphonate (4)4 have been employed as the activating reagent for carboxyl group.In a series study of achiral and chiral 1.3-thiazolidine-2-thiones, we developed a dehydrating condensation reagent, 3.3'-(phenylphosphoryl)-bis(l,3-thiazolidine-2-thione) (PPTT) (5) which was useful not only for carboxylic amide formation (eq. 1) but also 1.3-thiazolidine-2-thione amide formation (eq. 2).5,6PPIT (5) was also efficiently exploited for the amide bond formation in the total synthesis of parabactin, a spermidine siderophore.