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 Image Number 3 for United States Patent #4649197.
A sulfate of tetrahydrobiopterin having the formula (I): ##STR1## and a process for preparing the same, which comprises crystallizing tetrahydrobiopterin from an aqueous medium containing sulfuric acid. The sulfate of the (6R)-form of (1) has a high crystallinity and the process easily gives a sulfate of the (6R)-form
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