J. Tomasz

Instability of the Phosphodiester-Amide Interribonucleotide Bond in Neutral Aqueous Solution

Abstract Ap(NH2)dT was synthesized as a model compound for a study of the stability of the phosphodiester-amide interribonucleotide linkage in neutral aqueous solution, by photolyzing AnBnp(NH2)dT in anhydrous p-dioxane. Ap(NH2)dT proved to be unstable even under anhydrous conditions and could not be isolated. It was rapidly decomposed in neutral aqueous buffer solution, at 25°C, to give A>p, dT and ApdT. Three unstable intermediates of this decomposition, A>pNH2, ApNH2 and A>pdT were detected by 31P NMR. On the basis of the structure of the products, a mechanism is proposed for the decomposition.

Evidence for the Stereoelectronic Control of the Acid Hydrolysis of Adenosine Cyclic 3′,5′-Phosphoramidate Diastereoisomers

Abstract The substitution by a methyl group of the axial 5′hydrogen atom of adenosine cyclic 3′,5′-phosphoramidate diastereoisomers significantly increases the P-N bond breaking for the R−p diastereoisomer, but does not change that for the S−p diastereoisomer as anticipated on the basis of ground state stereoelectronic effects.

Improved Synthesis of Adenosine Cyclic 3′, 5′-Phosphoramidates via Anhydrides. Preparation of Adenosine Cylic 3′, 5′-(Rp) - and (p)-N-Methylphosphoramidate

Abstract The two-step method for the preparation of adenosine cyclic 3′,5′-phosphoramidate diastereoisomers, which involves the activation of adenosine cyclic 3′,5′-monophosphate (1) with an acid chloride and in situ aminolysis of the anhydride intermediate (Bentrude, W.G.; Tomsaz, J. Synthesis 1984, 27; Bottka, S.; Tomasz, J. Tetrahedron Lett. 1985, 24, 2909), has been improved. The best yields were attained when 1 was reacted with 4.4 molar equivalents of phosphorus oxychloride in trimethyl phosphate at O°C for 3 h, and the solution of phosphorus oxychloride in trimethyl phosphate was pretreated with 0.5 molar equivalent of water at room temperature for 20 min. R p and S p diastereoisomers of adenosine cyclic 3′,5′-N-methyphosphoramidate and N,N-dimethylphosphoramidate have been synthesized under these experimental conditions.

Hydrolysis of Adenosine Cyclic 3′,5′-(Rp)- and (S p)-Phosphoramidates. Stereoelectronic Effects in the Acid Hydrolysis

Abstract Hydrolyses of R p and S p diastereoisomers of adenosine cyclic 3′,5′-phosphoramidate ( 1 ), -N-methylphosphoramidate ( 2 ) and -N, N-dimethylphosphoramidate ( 3 ) in 0.1 N sodium hydroxide and 0.1 N hydrochloric acid, respectively, have been studied. In 0.1 N sodium hydroxide, the ester bonds of the compounds are broken. In 0.1 N hydrochloric acid, despite predictions to the contrary, 1 hydrolyzes with predominant ester bond breakings, while 3 decomposes with exclusive amide bond fission. In the acid hydrolysis of 2 , cleavages of amide and ester bonds are of comparable degree. Significant differences exist between R p and S p diastereoisomers. The peculiar behavior of 1 and 2 in acid hydrolysis is interpreted on the basis of ground stite stereoelectronic effects.

P1-(Thymidine 5′-)P1-amino-triphosphate: Synthesis, Hydrolysis and Reaction with Cytidine in Alkali1

Abstract The title compound 1 is prepared from thymidine 5′-phos-phorodiamidate (2) and inorganic pyrophosphate (3) in anhydrous DMF, at 30–32°C. The products of alkaline hydrolysis of 1, at room temperature, are: thymidine 5′-phosphoramidate (4), thymidine 3′-phosphoramidate (8) and thymidine (9) as well as 3 and inorganic trimetaphosphate (10). In 1 N NH4OH, 1 reacts with cytidine (15) to form cytidylyl-/2T(3′)-5′/-thymidine (16) and a mixture of cytidine 2′,3′-cyclic phosphate (17) and 9.

3′-3′,3′-5′ and 5′-5′ TpT-Amides: Synthesis, Characterization and Alkaline Hydrolysis

Abstract A simple procedure is described for the preparation of the title compounds 1, 8 and 9. 3′-3′ or 3′-5′ or 5′-5′ TpT was reacted with a twofold molar excess of TPS in anhydrous DMF, at room temperature, for 5 min, followed by a 1 min in situ treatment of the reaction mixture with excess 7.0 N NH4OH, at 0°C. The alkaline hydrolysis of 1, 8 and 9 proceeds without the assistance of 3′- and 5′-hydroxyl groups resulting in equimolar mixtures of thymidine (4) and thymidine 3′-phosphoramidate (6) (for the 3′-3′ isomer) or thymidine 5′-phosphoramidate (7) (for the 5′-5′ isomer) or 6 and 7 in equal quantities (for the 3′-5′ isomer).

Adenosine Cyclic 3′, 5′-Phosphoramidate and N,N-Dimethylphosphoramidate: Synthesis Via Symmetrical and Mixed Anhydrides and Hydrolysis

Abstract The title compounds were synthesized by converting cyclic AMP with a sulfonyl chloride to the symmetrical anhydride or with diphenyl phosphorochloridate to the mixed anhydride, then aminolyzing the anhydrides without isolation. The synthesis preferentially gave Sp-amides. Characteristic differences were observed in the behavior of the unsubstituted amide and the dimethylamide under hydrolysis conditions.

A 31p NMR study of the reaction of adenosine 3′,5′-cyclic monophosphate with 2,4,6-triisopropylbenzenesulfonyl chloride

Abstract The reaction of adenosine 3′,5′-cyclic monophosphate (cyclic AMP) with 0.5–2.0 molar equivalents of 2,4,6-triisopropylbenzenesulfonyl (p-toluenesulfonyl or mesitylenesulfonyl) chloride leads to the rapid formation of the three possible phosphorus diastereoisomers [RPRP, SPSP and RPSP (SPRP)] of cyclic AMP symmetrical anhydride. The diastereoisomers were characterized by 31P NMR. The cyclic AMP sulfonic mixed anhydride could not be detected.

Cyclic AMP Diphenyl Phosphoric Mixed Anhydride: Synthesis, P NMR Characterization and Reaction with Dimethylamine

Abstract Phosphorus diastereoisomers, R p and S p of p1-adenosine cyclic 3′, 5′ P2 -diphenylpyrophosphate (cyclic AMP diphenylphosphoric mixed anhydride) (1) were prepared from adenosine cyclic 3′, 5′-monophosphate (cyclic AMP) and diphenyl phosphorochloridate and characterized by 31p NMR. The synthesis preferentially gave R p-1. Reaction of 1 with dimethylamine resulted in the formation of a (∼ 3:1) mixture of adenosine cyclic 3′,5′-N, N-dimethylphosphoramidate and diphenyl-N, N-dimethylphosphoramidate and occurred with inversion of configuration at cyclic AMP phosphorus.

A Possible Mechanism for the Base-Catalyzed Hydrolysis of Nucleoside Cyclic 3′,5′-Monophosphates

Abstract The predominant formation of nucleoside 3′-mono-phosphates in the base-catalyzed hydrolysis of nucleoside 3′,5′-monophosphates is interpreted in terms of the lone pair orientation effect that may decrease the transition state energy for P-O-C5′ bond breaking.