79974-37-1Relevant articles and documents
Synthesis of Certain Fluorescent Tricyclic Nucleosides Derived from PyrazoloPyrimidine Nucleosides
Bhat, Ganapati A.,Townsend, Leroy B.
, p. 2387 - 2393 (2007/10/02)
The synthesis of certain tricyclic nucleosides with a dihydroimidazole, imidazole, triazole, or tetrazole ring fused to the pyrazolopyrimidine ring system in an angular position (C-4 and N-5) has been accomplished.The 4-aziridinyl derivative (2) was prepared by a nucleophilic displacement of the chlorine atom of 4-chloro-1-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)pyrazolopyrimidine (1) with ethylenimine.The nucleoside (2) was then treated with sodium iodide to furnish 7-(β-D-ribofuranosyl)-2,3-dihydroimidazopyrazolopyrimidine (3).The reaction of (1) with lithium azide gave 7-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)pyrazolotetrazolopyrimidine (5) and cyclization of 4-amino-1-(β-D-ribofuranosyl)pyrazolopyrimidine with chloroacetaldehyde provided the tricyclic nucleoside 7-(β-D-ribofuranosyl)imidazopyrazolopyrimidine (7). 2,4-Dinitrophenoxamine was treated with 4-amino-1-(β-D-ribofuranosyl)pyrazolopyrimidine (6) to give an intermediate (8) which on cyclization with diethoxymethyl acetate gave 7-(2,3-O-methoxymethylene-β-D-ribofuranosyl)pyrazolo-1,2,4-triazolopyrimidine (9).Acid-catalysed deblocking of (9) provided the desired tricyclic nucleoside (10).The reaction of trimethyl orthoformate with 4-hydrazino-1-(β-D-ribofuranosyl)pyrazolopyrimidine under different experimental conditions resulted in the formation of a mixture of diastereoisomers due to the 2',3'-O-methoxymethylene group.Treatment of (10) with alkali gave a ring-opened intermediate which on treatment with sodium nitrite and acetic acid cyclized to give an aza-derivative (16) of (10).
