220ChemInform Abstract The 1:2 molar reaction of the betaine salt (I) with the prim. amines (II) leads to the pyridinium 1-alkyl-2-alkylamino-azathiadiphosphetidinethiolates (III) which react with MeI (IV) to give the corresponding methyl esters (V) and (VI). From sterically demanded amines (II) the trans and cis isomers (Va)/(VIa) and (Vb)/(VIb) are obtained, whereas n-alkyl-and allylamines (IIc) only afford the trans isomers (Vc). The structures of (Va) and (VIa) (for both space group P1, Z=2) are determined by X-ray analysis.