Stereoselective deamination of (5′RS)-5′-methyl-2′,3′-isopropylidene adenosine catalyzed by adenosine deaminase: preparation of diastereomerically pure 5′-methyl adenosine and inosine derivatives

Structural Basis of Duplex Thermodynamic Stability and Enhanced Nuclease Resistance of 5'-C-Methyl Pyrimidine-Modified Oligonucleotides

Although judicious use of chemical modifications has contributed to the success of nucleic acid therapeutics, poor systemic stability remains a major hurdle. The introduction of functional groups around the phosphate backbone can enhance the nuclease resistance of oligonucleotides (ONs). Here, we report the synthesis of enantiomerically pure (R)- and (S)-5'-C-methyl (C5'-Me) substituted nucleosides and their incorporation into ONs. These modifications generally resulted in a decrease in thermal stability of oligonucleotide (ON) duplexes in a manner dependent on the stereoconfiguration at C5' with greater destabilization characteristic of (R)-epimers. Enhanced stability against snake venom phosphodiesterase resulted from modification of the 3'-end of an ON with either (R)- or (S)-C5'-Me nucleotides. The (S)-isomers with different 2'-substituents provided greater resistance against 3'-exonucleases than the corresponding (R)-isomers. Crystal structure analyses of RNA octamers with (R)- or (S)-5'-C-methyl-2'-deoxy-2'-fluorouridine [(R)- or (S)-C5'-Me-2'-FU, respectively] revealed that the stereochemical orientation of the C5'-Me and the steric effects that emanate from the alkyl substitution are the dominant determinants of thermal stability and are likely molecular origins of resistance against nucleases. X-ray and NMR structural analyses showed that the (S)-C5'-Me epimers are spatially and structurally more similar to their natural 5' nonmethylated counterparts than the corresponding (R)-epimers.

2',3'-isopropylidene group, a molecular scaffold to study the activity of adenosine and adenylate deaminase on adenosine analogues modified in the ribose moiety

2 ',3 '-Isopropylidene group can be used as a molecular scaffold for the introduction of modifications at 5 ' and 1 ' positions of adenosine and these modified nucleosides are used to evaluate the biocatalytic activity of adenosine and adenylate deaminase.

Facile and Rapid Access to Inosine Puromycin Analogues through the Use of Adenylate Deaminase

To study the ribosomal peptidyl transfer, puromycin analogues are of interest in which adenine has been replaced by hypoxanthine. We synthesized inosine puromycin analogues from 3'-azidodeoxyadenosine derivatives using adenylate deaminase for the quantitative transformation of the N-heterocycle. The amino acid coupling was carried out under Staudinger-Vilarrasa conditions in 94% yield starting from the protected and in 82% using the unprotected azide, thus, in the presence of two hydroxyls and a lactam function.

Deamination of 2',3'-O-isopropylideneadenosine-5'- carboxylic acid catalyzed by adenosine deaminase (ADA) and adenylate deaminase (AMPDA): influence of substrate ionization on the activity of the enzymes

Adenosine deaminase (ADA) and adenylate deaminase (AMPDA) catalyze the deamination of 2 ',3 '-O-isopropylideneadenosine-5'-carboxylic acid to the corresponding inosine derivative and dependence of the rate of enzymatic reaction on the ionization degree of the substrate has been studied at different pH values.

Adenosine Deaminase in Nucleoside Synthesis. A Review

Adenosine deaminase (ADA) is an enzyme in the purine salvage pathway that catalyzes the deamination of adenosine and deoxyadenosine to inosine and deoxyinosine, respectively. This deamination is an important factor in limiting the usefulness of adenosine analogues in chemotherapy. However, the biocatalysis by ADA is also a useful transformation in enzymatic synthesis. In this review, examples from both the principal investigator's laboratory and from the literature, which depict the synthetic usefulness of this enzyme in deamination, dehalogenation, demethoxylation reactions and in diastereoisomeric resolution, are presented. It is not the intent of this review to comprehensively list all of the biotransformations induced by adenosine deaminase, but rather to present representative examples to highlight the powerful synthetic utility of this enzyme. A review with 72 references.