| Popis: |
The modified nucleic acid base, 6-amino-3-methyl-5-(N-formylamino)uracil is one of three new modified uracil derivatives isolated and extracted from human urine in our laboratory. X-ray crystallographic investigation was undertaken to understand the cis-trans isomerization of the N-formylamino group about the C(ring)-N(formyl) bond. Crystals of the title compound are monoclinic, space group, P21/n, with unit cell dimensions a=16.932(2), b=10.565(1), C=4.298(1)A, β=91.1(1)°, Z=4, Dobs=1.59 g.cm−3, Dcslc=1.591 g cm−3. Complete three dimensional data (2θ≤150° for CuKα) were collected on a CAD-4 diffractometer by the ω/2θ scan method. The structure was solved by a straight forward application of multisolution techniques and refined by full-matrix least-squares method to a final R value of 0.044. The amino group at the 6-position is in the plane of the uracil ring, but the N-formyl amino group at the 5-position is twisted away from the uracil plane by ±82.2°, a conformation about half-way between the ... |
