A Direct Route to 3‐(<scp>D</scp>‐Ribofuranosyl)pyridine Nucleosides

Abstract

Abstract A route for synthesizing C ‐nucleosides with 2,6‐substituted pyridines as heterocyclic aglycones is described. Condensation of appropriately substituted lithiated pyridines with ribono‐1,4‐lactone derivatives yields hemiacetal 4a – g ( Table 1 ), which can be reduced by Et 3 SiH and BF 3 ·Et 2 O to the corresponding C ‐nucleoside (see Scheme 1 for 4d → β‐ D ‐ 5 ). Conditions are presented that optimize the amount of the 2,6‐dichloropyridine‐derived β‐ D ‐anomer β‐ D ‐ 5 formed ( Table 3 ). Aminolysis of β‐ D ‐ 5 yields the diaminonucleoside 14 ( Scheme 3 ).