A solution of 7.88 g (10 mmole) of the pentabenzoyl adenosine (1A) in 150 ml dry pyridine and 50 ml dry MeOH was treated with 50 ml 1M sodium methylate solution. After 15 min the solution was poured onto an ice cold solution of a 110 ml DOWEX ion exchanger 50×4 (pyridinium form) in ca 20 ml water. After 5 h stirring the pH was 5.5-6.0. After filtering from the ion exchanger, the residue was washed with boiling MeOH/water (3/1). The filtrate was evaporated to dryness and crystallized from MeOH/water 2/1 to give 3.25 g (83%) of the product as colorless needles, m.p. 151°-153° C.
