Nucleic acid related compounds.: 108.: Biomimetic modeling of the abstraction of H3′ by ribonucleotide reductases.: 1,5-hydrogen atom transfer of H3 to aminyl and oxyl, but not thiyl, free radicals in homoribofuranose derivatives

Generation of 6-oxyl radicals from homoribofuranose (5-deoxy-D-ribo-hexofuranose) 6-O-nitro esters with Bu3SnD/AIBN/benzene/Delta resulted in abstraction of H3 by a [1,5]-hydrogen atom shift. Transfer of H-2 from the stannane to . C3 effected incorporation of deuterium at C3. Analogous treatment of 6-azido-6-deoxy-D-ribo-hexofuranose derivatives gave C3-deuterated aminosugars. In contrast, no deuterium incorporation was detected upon parallel treatment of 6-thio-D-ribo-hexofuranose derivatives. Abstraction of H3' by a thiyl radical (. SCys) is the postulated first step in reactions that are utilized by ribonucleotide reductases to convert ribonucleotides into 2'-deoxynucleotides. Results are discussed relative to the enzyme reaction cascade that couples abstraction of H3' with irreversible loss of water from C2'. (C) 1999 Elsevier Science Ltd. All rights reserved.