Bisphosphonate derivatives of nucleoside antimetabolites: hydrolytic stability and hydroxyapatite adsorption of 5'-beta,gamma-methylene and 5'-beta,gamma-(1-hydroxyethylidene) triphosphates of 5-fluorouridine and ara-cytidine.
Kinetics of the hydrolytic reactions of four bisphosphonate derivatives of nucleoside antimetabolites, viz., 5-fluorouridine 5'-beta,gamma-(1-hydroxyethylidene) triphosphate ( 4), 5-fluorouridine 5'-beta,gamma-methylene triphosphate ( 5), ara-cytidine 5'-beta,gamma-(1-hydroxyethylidene) triphosphate ( 6), and ara-cytidine 5'-beta,gamma-methylene triphosphate ( 7), have been studied over a wide pH range (pH 1.0-8.5) at 90 degrees C. With each compound, the disappearance of the starting material was accompanied by formation of the corresponding nucleoside 5'-monophosphate, the reaction being up to 2 orders of magnitude faster with the beta,gamma-(1-hydroxyethylidene) derivatives ( 4, 6) than with their beta,gamma-methylene counterparts ( 5, 7). With compound 7, deamination of the cytosine base competed with the phosphate hydrolysis at pH 3-6. The measurements at 37 degrees C (pH 7.4) in the absence and presence of divalent alkaline earth metal ions (Mg (2+) and Ca (2+)) showed no sign of metal ion catalysis. Under these conditions, the initial product, nucleoside 5'-monophosphate, underwent rapid dephosphorylation to the corresponding nucleoside. Hydrolysis of the beta,gamma-methylene derivatives ( 5, 7) to the corresponding nucleoside 5'-monophosphates was markedly faster in mouse serum than in aqueous buffer (pH 7.4), the rate-acceleration being 5600- and 3150-fold with 5 and 7, respectively. In human serum, the accelerations were 800- and 450-fold compared to buffer. In striking contrast, the beta,gamma-(1-hydroxyethylidene) derivatives did not experience a similar decrease in hydrolytic stability. The stability in human serum was comparable to that in aqueous buffer (tau 1/2 = 17 and 33 h with 4 and 6, respectively), and on going to mouse serum, a 2- to 4-fold acceleration was observed. To elucidate the mineral-binding properties of 4- 7, their retention on a hydroxyapatite column was studied and compared to that of zoledronate ( 1a) and nucleoside mono-, di-, and triphosphates.
Ora
Mikko
M
Department of Chemistry, University of Turku, Turku, Finland.
Lönnberg
Tuomas
T
Florea-Wang
Diana
D
Zinnen
Shawn
S
Karpeisky
Alexander
A
Lönnberg
Harri
H
D000327:Adsorption; D000818:Animals; D002118:Calcium / Q000737:chemistry; D003562:Cytidine / Q000097:blood*; D004164:Diphosphonates / Q000737:chemistry*; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry; D051379:Mice; D009705:Nucleosides / Q000737:chemistry*; D014529:Uridine / Q000031:analogs & derivatives* / Q000097:blood
D004164:Diphosphonates; D009705:Nucleosides; C001943:5-fluorouridine; D003562:Cytidine; D008274:Magnesium; D002118:Calcium; D014529:Uridine