New and Facile Synthesis of 5,6,7,8-Tetrahydro-5-deaza-5-thiapterins via the Aliphatic S-N Type Smiles Rearrangement.

5, 6, 7, 8-Tetrahydro-5-deaza-5-thiapterins, (1a, 1d, and 1e), were conveniently synthesized by the thermal condensation of 5-bromo-6-chloroisocytosine (5) with cysteamines (6a-c) via the aliphatic S-N type Smiles rearrangement in ethanolic pH 7.0 buffer solution.