A convenient synthesis of 2'-deoxy-6-thioguanosine, ara-guanine, ara-6-thioguanine and certain related purine nucleosides by the stereospecific sodium salt glycosylation procedure [1]

Article abstract of DOI:10.1002/jhet.5570250653

A simple and high-yield synthesis of biologically significant 2'-deoxy-6-thioguanosine, ara-6-thioguanine and araG has been accomplished employing the stereospecific sodium salt glycosylation method. Glycosylation of the sodium salt of 6-chloro- and 2-amino-6-chloropurine (1 and 2, respectively) with 1-chloro-2-deoxy-3,5-di-O-(p-toluoyl)-α-D-erythro-pentofuranose gave the corresponding N-9 substituted nucleosides as major products with the β-anomeric configuration (4 and 5, respectively) along with a minor amount of the N-7 positional isomers (6 and 7). Treatment of 4 with hydrogen sulfide in methanol containing sodium methoxide gave 2'-deoxy-6-thioinosine in 93% yield. Similarly, 5 was transformed into 2'-deoxy-6-thioguanosine (β-TGdR, 11) in 71% yield. Reaction of the sodium salt of 2 with 1-chloro-2,3,5-tri-O-benzyl-α-D-arabinofuranose gave N-7 and N-9 glycosylated products 13 and 9, respectively. Debenzylation of 9 with boron trichloride at -78° gave the versatile intermediate 2-amino-6-chloro-9-β-D-arabinofuranosylpurine 62% yield. Direct treatment of 14 with sodium hydrosulfide furnished ara-6-thioguanine. Alkaline hydrolysis of 14 readily gave 9-β-D-arabinofuranosylguanine (araG, 17), which on subsequent phosphorylation with phosphorus oxychloride in trimethyl phosphate afforded araG 5'-monophosphate.