Highly Stereoselective Total Syntheses of 2,5‐Anhydro‐4‐deoxy‐ D ‐ ribo ‐hexonic Acid and of (1 S )‐1‐ C ‐(6‐amino‐7 H ‐purin‐8‐yl)‐1,4‐anhydro‐3‐deoxy‐ D ‐ erythro ‐pentitol (= cordycepin C)

Highly regio‐ and stereoselective monohydroxylation of the CC bond of (+)‐7‐oxabicyclo[2.2.1]hept‐5‐en‐2‐one ( 8 ) was achieved via LiAlH 4 reduction of the corresponding 5,6‐ exo ‐epoxy dimethyl acetal 9 . The reaction gave exclusively (–)‐(1 R , 2 R , 4 S )‐6,6‐dimethoxy‐7‐oxabicyclo[2.2.1]heptan‐2‐ exo ‐ol ( 10 ) which was transformed into 2,5‐anhydro‐3‐ O ‐benzyl‐4‐deoxy‐ D ‐ ribo ‐hexonic acid ( 15 ) and 2,5‐anhydro‐4‐deoxy‐ D ‐ ribo ‐hexonic acid ( 6 ) via ozonolysis of (–)‐(1 R , 4 S , 6 R )‐6‐ exo ‐benzyloxy‐2‐{[( tert ‐butyl)dimethylsilyl]oxy}‐7‐oxabicyclo[2.2.1]hept‐2‐ene ( 14 ). Cordycepin C ( 5 ) was derived from 6 and 4,5,6‐triaminopyrimidine using CsF/DMF to generate the adenine heterocycle.