Abstract: The phosphoryl N→O migration reaction and ester exchange reaction on phosphorus of phosphoserine with methyl alcohol involving hexa coordinate phosphorus intermediate 3 had been studied by MNDOmethod. The three isomers structures of 3 were discussed in detail based on the calculation results. Among the six bonds in3, the P_O bond between the phosphorus and carboxyl oxygen O3 was the weakest one, and could be easily broken to form a new penta coordinate intermediate 4 which could yield the phosphoryl N→Omigration product 5 by breaking the weaker P_N bond. For these two iso propoxyl groups that bonded to phosphorus in3, the one situated opposite to O6 of serine side chain, was easier to leave than the other one by about 37 kJ/mol to produce the intermediate 6. Then a methanol could attack phosphorus of 6 from this new formed vacancy position to yield the ester exchanged product. Thus, the hexa-coordinate phosphorus intermediate mechanism could be used to explain various bio mimic reactions for phosphoserine.

Key words: Hexa-coordinate phosphorus intermediate, MNDO, Phosphoryl N→O migration, Ester exchange reaction on phosphorus