Journal of the Chemical Society. Perkin transactions I p. 2387 - 2393 (1981)
Update date:2022-08-02
Topics:
Bhat, Ganapati A.
Townsend, Leroy B.
The synthesis of certain tricyclic nucleosides with a dihydroimidazole, imidazole, triazole, or tetrazole ring fused to the pyrazolo<3,4-d>pyrimidine 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)pyrazolo<3,4-d>pyrimidine (1) with ethylenimine.The nucleoside (2) was then treated with sodium iodide to furnish 7-(β-D-ribofuranosyl)-2,3-dihydroimidazo<1,2-c>pyrazolo<4,3-e>pyrimidine (3).The reaction of (1) with lithium azide gave 7-(2,3,5-tri-O-acetyl-β-D-ribofuranosyl)pyrazolo<4,3-e>tetrazolo<1,5-c>pyrimidine (5) and cyclization of 4-amino-1-(β-D-ribofuranosyl)pyrazolo<3,4-d>pyrimidine with chloroacetaldehyde provided the tricyclic nucleoside 7-(β-D-ribofuranosyl)imidazo<1,2-c>pyrazolo<4,3-e>pyrimidine (7). 2,4-Dinitrophenoxamine was treated with 4-amino-1-(β-D-ribofuranosyl)pyrazolo<3,4-d>pyrimidine (6) to give an intermediate (8) which on cyclization with diethoxymethyl acetate gave 7-(2,3-O-methoxymethylene-β-D-ribofuranosyl)pyrazolo<4,3-e>-1,2,4-triazolo<1,5-c>pyrimidine (9).Acid-catalysed deblocking of (9) provided the desired tricyclic nucleoside (10).The reaction of trimethyl orthoformate with 4-hydrazino-1-(β-D-ribofuranosyl)pyrazolo<3,4-d>pyrimidine 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).
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Doi:10.1016/0584-8539(81)80119-5
(1981)Doi:10.1016/S0008-6215(00)87152-9
(1981)Doi:10.1021/jo00345a020
(1982)Doi:10.1002/hlca.19810640619
(1981)Doi:10.1021/acs.joc.0c02093
(2020)Doi:10.1016/S0040-4039(01)81985-7
(1981)
