Regioselective alkylation of guanine, a long-lasting challenge, has been overcome by understanding the role of acids as catalyst in the coupling reaction of DAG (10) with OBDDA (11). The acid-catalyzed and noncatalyzed reactions of 10 with OBDDA which mainly give N(7) and N(9) isomers, respectively, appear to follow different mechanisms. The practical utility of the noncatalyzed reaction, which gives almost quantitative yields of N(9) derivatives, is demonstrated by synthesizing acylovir/gancyclovir in high yields.

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react with thiourea in refluxing ethanol to yield the corresponding N-aryl ct-(2,3,4,5-tetrahydro-4-oxo-l,3-thiazole-5-yl) acetamides (6a-j_') in 72-85~o. The spectral and analytical data are consistent with the assigned structures for 6a-j. Under similar conditions, isomalemides 3(~-_b and 3d--f) furnish the corresponding 6a-_b and 6d-f in 76-86~. While maleanilic acid (4_.a) itself failed to react with thiourea, 4b--e_, 4i and 4j yielded a mixture of the corresponding 6___~e, 6i and 6j in 2-50~o and fumaranilic acids (7b--e_, 7i and 7j) in 50-80~. Methyl maleanilates 5~, 5d-f and ~ gave 6b,6d-_f and 6i in 78-85~. The reaction course of Raney nickel desulphurisation of 6a-_b, ~ 6f and mass spectral fragmentation of 6b support the assigned structures.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.