This work was done employing theoretical and experimental methodologies to show synthesis process of new compounds in addition to evaluating their features. In this case, phosphorus ylide intermediates were initially resulted from the three-component reaction between dialkyl acetylenedicarboxylate and theophiline in the presence of phosphits ((R’O)۳P). Next, they were converted to stable diastereoisomeric beta-amidophosphonates. Density functional theory (DFT) calculations at the B۳LYP/۶-۳۱۱+G* level of theory indicated that (۲S, ۳S) and/or (۲R, ۳R) diastereomers of phosphonates were about ۱۸-۲۸ kcal/mol more stable than (۲R, ۳S) and/or (۲S, ۳R) diastereomers. As a consequence, the targeted compounds were synthesized and they very confirmed by performing DFT
calculations as an advantage of combinations of experimental and theoretical approaches for solving the problems in chemistry.