A Convenient Synthesis of New Purinyl-<i>homo</i>-carbonucleosides on a Cyclopentane Ring Fused with Pyridazine

The new purinyl homo-carbonucleosides 10 and 17a were prepared from 1,4-diphenyl-5,8-dihydro-5,8-methanophthalazine by one-pot ozonolysis and reductive cleavage, followed by monoprotection with an Ac or TBDMS group, mesylation of the resulting diol and replacement of the mesyl group with 6-chloropurine in the presence of NaH and 18-crown-6 ether. Homo-carbonucleosides 12 and 13 were then obtained from 10 by substitution of the chlorine in purine position 6. Compounds 17b and 19 were obtained from 17a in the same way.