Purines. LXV. Preparatory Study for the Syntheses of the Marine Sponge Purines Agelasimines-A and -B: Synthesis and Acetylation of Their N(7)-Benzyl Analogues.
Purines. LXV. Preparatory Study for the Syntheses of the Marine Sponge Purines Agelasimines-A and -B: Synthesis and Acetylation of Their N(7)-Benzyl Analogues.
Model Experiments for Acetylation of the Marine Sponge Purines Agelasimine-A and Agelasimine-B
作者:Tozo Fujii、Tohru Saito、Jun Chikazawa、Masashi Ohba、Tadamasa Date
DOI:10.3987/com-93-6640
日期:——
Reactions of 7-benzyl-N6,3-dimethyladenine (1b) and 7-benzyl-1,2-dihydro-1,3-dimethyladenine (2b), selected as models for the marine sponge alkaloids agelasimine-A (1a) and agelasimine-B (2a), with acetic anhydribe in pyridine have been studied. The product from 1b was the imidazole derivative (6b), whose structure was determined by an X-ray crystallographic analysis. The product from 2b was the N6-acetyl derivative (4b). On treatment with boiling H2O, 4b gave 7-benzyl-2,3-dimethylhypoxanthine (5b) and a compound presumed to be 11.
Purines. LXV. Preparatory Study for the Syntheses of the Marine Sponge Purines Agelasimines-A and -B: Synthesis and Acetylation of Their N(7)-Benzyl Analogues.
Four-step synthetic routes from 3-methyladenine (10) to 7-benzyl-N6, 3-dimethyladenine (1b) and 7-benzyl-1, 2-dihydro-1, 3-dimethyladenine (2b), selected as models for the marine sponge alkaloids agelasimine-A (1a) and agelasimine-B (2a), respectively, have been established. The key steps involved are regioselective methylations of 7-benzyl-3-methyladenine (8) and 7-benzyl-1, 2-dihydro-3-methyladenine (11). The reaction of 1b with acetic anhydride in pyridine was found to give the monocyclic imidazole derivative 29b. A similar acetylation of 2b yielded the N6-acetyl derivative 20b. When treated with boiling H2O, 20b afforded 7-benzyl-2, 3-dimethylhypoxanthine (21b) and a compound inferred to be the dihydrohypoxanthine derivative 30. Probable pathways to 29b from 1b and to 21b and 30 from 20b are proposed.