1.2.4- Triazolo pyrimidines molecular modelling

Ab initio molecular orbital calculations on these systems have been confined to the 1,2,3-triazolo[4,5-d]pyrimidines (7), the so-called 8-azapurines , and references to this subject may be found in the previously mentioned review <86AHC(39)ii7>. In 1989, quantum mechanical perturbation methods have been used to study the activity of 8-azapurine nucleoside antibiotics in transcription processes <89Mi 7i3-oi>. The l,2,3-thiadiazolo[5,4-d]pyrimidine derivative (51), a rearrangement product of 8-aza-6-thioinosine, has been used in a molecular modeling study of the antitumor activity of sugar derivatives of pyrimidopyrimidines <89PNA(86)8242>. 

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