The Determinative Influence of the O⁶-(Diphenylcarbamoyl) Group on the Exocyclic Nitrogen Benzylation in 2-Amino-6-oxopurine Derivatives

Abstract

A series of novel 2-(benzylamino)-6-oxopurine derivatives has been synthesized by arylalkylation of the corresponding 2-(acetylamino)-6-(diphenylcarbamoyloxy)purines. The decisive role of the temporary O⁶-(diphenylcarbamoyl) protection on the benzylation of the exocyclic amino group in 2-(acetylamino)-6-oxopurines has been demonstrated.

Key words

nucleobases - benzylation - protecting groups - substituent effects - synthesis

References

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11

For compounds 4d and 12 diffraction data were collected on a Nonius KappaCCD difractometer using graphite monochromated Mo-Kα radiation (λ = 0.71073 Å). The crystal structures of 4d and 12 were solved by the direct method and refined by full-matrix least squares. All non-hydrogen atoms were refined anisotropically.
Crystal data for 4d: C₃₄H₂₃BrCl₄N₆O₃, triclinic, a = 12.0270(6), b = 12.1093(6), c = 12.5269(7) Å, α = 73.074(2), β = 81.041(2), γ = 86.769(2)˚, V = 1724.0(2) Å^³, Z = 2, µ = 1.547 mm^-¹, D _calc = 1.513 g cm^-³, space group is P 1. A total of 6718 independent reflection intensities were collected at r.t. For structure refinement, 3497 reflections with I ≥ 2σ(I) were used. The final R-factor is 0.0680.
Crystal data for 12: C₁₉H₁₉Br₂N₅O₅, triclinic, a = 7.5419(4), b = 12.1920(8), c = 12.6754(10) Å, α = 105.193(2), β = 91.052(3), γ = 101.808(5) ˚, V = 1097.8(1) Å^³, Z = 2, µ = 3.733 mm^-¹, D _calc = 1.686 g cm^-³, space group is P 1. A total of 4560 independent reflection intensities were collected at r.t. For structure refinement, 2520 reflections with I ≥ 2σ(I) were used. The final R-factor is 0.0596. For further details, see crystallographic data for 4d and 12 deposited with the Cambridge Crystallographic Data Centre as Supplementary Publication Numbers CCDC 667860, 667861.