H. Bazin

An efficient synthesis of y-nucleoside (wyosine) by regiospecific methylation of n4-desmethylwyosine using organozinc reagent

The reaction of the organozinc reagent, produced by the reaction of CH2I2 + Zn(C2H5)2 + glyme in diethylether at 20 °C, regioselectively methylates the N4-nitrogen of N4-desmethylwyosine-triacetate 3 to give pure wyosine-triacetate 1e in 76% isolated yield; no trace of the isomeric N5 methylated product is found in the latter reaction. Synthesis of a new congener of Y-nucleoside 1f is also reported for the first time from compound 5 in a high overall yield using a similar procedure.

The use of 15N-NMR spectroscopy for assigning the structures of isomeric N7- and N9-substituted purines

An 15N-NMR study has shown a considerable difference in electronic structures between the isomeric N7 and N9 substituted purines. A comparison of 15N chemical shifts amongst the seven pairs of N7 and N9 isomers has revealed that (1) the N3 resonances are shielded by 18–20 ppm in an N9 isomers; (2) the amino nitrogens at the C-2 or at C-6 positions are always shielded by 3–4 ppm in the N7 isomers; (3) the N7 chemical shifts in the N7 isomers are always more shielded by 6–7 ppm than the N9 resonances in the N9 isomers. It has a also been found by protonation studies that the N9 of the N7 isomer is much more basic than the N7 of the N9 isomer.

Synthesis of 2'-deoxy-2'(s)-deuterio and 2'-deoxy-2'(r)-deuterio-β-d-nucleosides

Abstract Lithium aluminium deuteride (LAD) promoted ring-opening reactions of appropriately protected methyl 2,3-anhydro-α-D-ribofuranoside 2 and methyl 2,3-anhydro-β-D-lyxofuranoside 10 , gave 2-deoxy-2( S )-deuterio- erythro -pentose and 2-deoxy-2( R )- threo -pentose derivatives, 4a and 12a , respectively. Compounds 4a and 12a were subsequently converted to 2-deoxy-2(S)-deuterio- and 2-deoxy-2( R )-deuterio- erythro -pentofuranosyl chlorides, 8 and 17 respectively.Thymine, Cytosine, 6-chloropurine and 2-amino-6-chloropurine were then glycosylated with these α-chlorosugars, 8 and 17 , to give the corresponding stereospecifically labelled 2-deoxy-2( S )-deuterio- and 2-deoxy-2( R )-deuterio-β-D-nucleosides.

Fluorescence Properties of Y-Nucleoside Derivatives

Abstract Modified-base and modified N3-(β-D_-ribofuranoside) derivatives of the Y base exhibit subnanosecond fluorescence decays. Attachment of groups to the “unnatural” N1 base position produces compounds showing dominant 7 - 10 ns decays. These spectral properties have been compared with those of the free Y base and suggest that the free Y base exists mainly as the N1-H tautomer.

On the Structure and Reactivity of Y-Nucleoside [Wyosine]

Abstract Wyosine-Triacetate 4 has found to undergo electrophilic reactions exclusively at the C-7 position. 15N-NMR of 4, shows that the primary site of protonation is N-5 suggesting that the “right” imidazole ring is more aromatic that the “left” imidazole moiety.