PREPARATION, STRUCTURAL CHARACTERIZATION, AND ACID-CATALYZED ISOMERIZATION OF 3-BENZYL-6-BENZYLTHIOPURINES, 7-BENZYL-6-BENZYLTHIOPURINES, AND 9-BENZYL-6-BENZYLTHIOPURINES

Benzylation of 6-benzylthiopurine was examined. Structural assignments of the products were determined by 1-D and 2-D nmr spectroscopy (HMQC , HMBC, and nOe). In the presence of base, the isomeric N3-, N7-, and N9-benzylated products 4, 3, and 2 were isolated; however, only 9-benz yl-6-benzylthio-purine (2) was obtained in the absence of base. In the latter case, the initially formed N3- and N7-isomers were, in the pre sence of acid, converted to 9-benzyl-6-benzylthiopurine (2) via a 6-be nzylthiopurine intermediate as evidenced by analysis of the reaction o ver time using reversed-phase hplc.