6- Amino-2-chloro-7-methylpurine

A further example (the oldest recorded) of isomerization, which differs from the preceding two examples, is credited to Fischer," who attempted the hydrolysis of the chlorine atom of 6-amino-2-chloro-7-methylpurine (54, R = H) with alkali but obtained 7-methylguanine (55, R = H) instead of 7-methylisoguanine. Some insight into the intramolecular rearrangement may be gained from the fact that the... 

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