Approach to Artificial Nucleosides from Glycoside Isothiocyanates: Synthesis of Original N-Glycosylated Heterostructures by Cyclocondensation Reactions

Unusual purine nucleoside analogues were synthesized, using the well-tried methodology in heterocyclic chemistry. This result expands the scope of accessible N-glycosylated heterocyclic structures. Pyrimidine, and bicyclic pyrimido[1,2-a]pyrimidine nucleoside analogues were prepared from common glycoside isothiocyanate precursors. Key cyclization steps were all based on a cyclocondensation reaction involving an activated heterodienic chain. Finally, thirteen pyrimido[1.2-a]pyrimidine nucleoside analogues 13 a-m were synthesized with a 30% yield on average, over 8 or 9 steps from one of the isothiocyanates 4 a-c. These elaborated targets were fully characterized.