Conformations and properties of O-Alkyl-S-(2-N,N-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH3P(O)(OR)(SCH2CH2NR (2) (') ), where (I) R = i-C4H9, R' = C2H5 and (II) R = C2H5, R' = i-C3H7, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.