Stereoselective synthesis of 3′-substituted 2′-deoxy C-nucleoside pyrazolo[1,5-a]-1,3,5-triazines and their 5′-phosphate nucleotides

An efficient synthesis of novel 3′-substituted 2′,3′-dideoxynucleoside analogues in the pyrazolotriazine series was developed from the corresponding 3′-ketonucleoside via the Wittig reaction. On the other hand, a highly stereoselective addition of alkynylcerium reagents to the same precursor led to the 3′-alkynyl-2′-deoxynucleosides in one step with the natural stereochemistry. Applications to produce novel P2Y1 receptor antagonists or new anti-retroviral nucleoside analogues are suggested.