Derivatives of adenosine 5'-phosphate (AMP) have been synthesized in which the phosphoester (POCH2) grouping of AMP is replaced by PCH(R)CH2 where R is OC(O)Me, CH2NHCOMe, CH2NHCOEt, and CH2NHCOOR' (R' = Me, Et, and Pr). The 2',3'-O-isopropylidene and 2', 3'-di-O-acetyl derivatives of AMP were also prepared. All compounds were competitive inhibitors of rabbit muscle AMP aminohydrolase with enzyme-inhibitor dissociation constants (Ki values) of 330, 20, 17, 19, 16, 14, 260, and 105 muM, respectively. All compounds were substrates except those in which R was CH2NHCOEt and CH2NHCOOR' (R'=Me, Et, and Pr). The previously described allo and talo epimers of 5'-C-acetylaminomethyl-AMP and the allo epimer of 5'-C-propionylaminomethyl-AMP were substrates and competitive inhibitors with Ki values of 18, 47, and 42 muM, respectively. The talo epimer of 5'-C-propionylaminomethyl-AMP was not a substrate and was a noncompetitive inhibitor, Ki