5-substituted pyrimidine L-2'-deoxyribonucleosides: synthetic, quantum chemical, and NMR studies

As a part of an ongoing medicinal chemistry, we report here the synthesis and structure evaluation of 1-(2-deoxy-3,5-di-O-acetylpentofuranosyl)-5-[(3-methyl-5-oxo-1-phenyl-4,5-dihydro-4H-pyrazol-4-ylidene) pyrimidine-2,4(1H,3H)-dione 5 and 5-[bis(3-methyl-5-oxo-1-phenyl-4,5-dihydro-4H-pyrazol-4-yl)methyl-1-(2-deoxy-3,5-di-O-acetylpentofuranosyl)pyrimidine-2,4(1H,3H)-dione 6 derived from 3',5'-di-O-acetyl-5-formyl-2'-deoxy-β-L-uridine 1. Base hydrolysis of compounds 1 and 6 furnished their deacetylated analogues in good yields, whereas hydrolysis of 5 was troublesome. Structural features of these molecules are discussed by NMR spectra analyses and density functional theory quantum chemical calculations. The newly synthesized L-analogues show no significant activity against vaccinia and cowpox viruses.