Ab initio studies on structures of the hexa-coordinate phosphorus intermediate for the phosphoryl ester exchange and N → O migration reactions of dimethyloxyphosphoryl-threonine

Recently observed unusual chemical reactivities of the N-phosphoryl amino acids reveal a special hexa-coordinate phosphorus intermediate may exist in the reaction process. It looks unstable and has not been observed directly. We report results obtained from ab initio studies of dimethyloxyphosphoryl-threonine and the corresponding hexa-coordinate phosphorus intermediate. The calculated results show that the hexa-coordinate phosphorous intermediate is a stable structure and all the PO and PN bonds in the intermediate should be much more active. From the calculated results, it is very easy to understand the observed reactivities of dimethyloxyphosphoryl-threonine and other similar dialkyloxyphosphoryl amino acids.