THE SYNTHESIS OF A TRICYCLIC PYRROLOPYRIMIDINE RELATED TO N-6-HYDROXYADENINE

The synthesis of ylpyrrolo[4,3,2-de]pyrimido[4,5-c]dihydrooxazepine 34 , a tricyclic pyrrolo[2,3-d]pyrimidine analogue of the mutagenic purin e N-6-hydroxyadenine, and several novel pyrrolo[2,3-d]pyrimidines is d escribed, The presence of the third ring constrains the amino substitu ent of 34 to arn anti orientation and is expected to improve dramatica lly the base-paining characteristics of the analogue with both cytosin e and thymine when present in DNA, An intramolecular cyclisation react ion of ethyl-2-methylsulfonyl-7H-pyrrolo[2,3-d]pyrimidine 30 gave 33, which was converted into the target molecule 34 via the displacement o f the methylsulfonyl group with hydrazine followed by oxidation of the hydrazino group with mercuric oxide. An analogous cyclisation with hy l)-4-chloro-7-methyl-7H-pyrrolo[2,3-d]pyrimidine 31 was less effective , whilst the corresponding 2-amino derivative 32 failed to cyclise.