The immediate（3） was prepared via three steps: at first substitutionof diethyl phosphonite,as the initial material,followed by addition-elimination.After Michael Reaction withdiethylmalonate,hydrolyzation and decarboxylation,（3） converted into key immediate（6）,which was subsequentlyconjugated with Melphalan and specifically phosphonate cleaved.Then thetitle conjugate Awas achieved.Its structure was verified by（）1HNMR,IR,MS and it showed good bone targeting ability via hydroxyapatite adhesion testsin vitro.
