1,3,5-Triazine cyclic acetals

Triazines are generally more reactive in [2 + 4] cycloaddition in comparison with 1,2,3-tria-zines. The wide variety of dienophiles can be employed enamines, enaminones, vinyl silyl ethers, vinyl thioethers, cyclic ketene jV,O-acetals, /V-phenylmaleimide, 6-dimethylaminopentafulvene, 2-alkylidene-imidazolidines (cychc ketene aminals), cyclic vinyl ethers, arynes, benzocyclopropene, acetylenes, and alkenes like ethylene, (Z)-but-2-ene, cyclopentene, cyclooctene and bicyclo[2.2.1]hept-2-ene, hexa-1,5-diene, cycloocta-1,5-diene, diallyl ether, cyclododeca-l,5,9-triene,... 

The acyclo C-nucleoside 811 was prepared in a closely similar plan to that used for the synthesis of its cyclic analog 808. [2-(Benzoyloxy)ethoxy]-acetic acid was condensed with 6-aminomethyl-l,2,4-triazin-5-one to give amide 810, which was then cyclized and de-C>-benzoylated to 811. This truncated sugar acyclo C-nucleoside did not inhibit herpes simplex viruses (HSV-1 and HSV-2) in cell culture (84JHC697) (Scheme 213). 

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