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Abstract

Heating 1-(2,3-di-O-benzoyl-β-D-arabinofuranosyl)-N⁴-benzoylcytosine (I) in 80% acetic acid afforded 1-(2,3-di-O-benzoyl-β-D-arabinofuranosyl)-N³-benzoylcytosine (II). Benzoylation of 5'-O-tritylcytidine (V) led to the 2',3',N⁴-tribenzoyl derivative VI which was refluxed with 80% acetic acid to give 2',3',N³-tribenzoylcytidine (VII). Analogously, 2',3',5',N⁴-tetrabenzoylcytidine (IX), prepared by benzoylation of cytidine with benzoyl cyanide, gave on reflux with 80% acetic acid 2',3',5',N³-tetrabenzoylcytidine (X). Under identical conditions, 1-methyl-N⁴-benzoylcytosine (XI) afforded directly 1-methyluracil (XII) .This migration takes place also in acetyl derivatives of cytosine nucleosides: 2',3',5',N⁴-tetraacetylcytidine (XIII) was transformed to the N³-acetylcytosine derivative XIV. On the other hand, migration of acetyl or benzoyl group from the exo-amino group of adenine has not been observed under the mentioned conditions. The migration of the N⁴-acyl group of cytosine derivatives proceeds best in aqueous acetic acid, more slowly also in anhydrous acetic acid, but not by action of trifluoroacetic acid in 1,2-dichloroethane.