Pteridine. Teil XCIV. Synthese und Eigenschaften von 5,6-Dihydro-6-(1,2,3-trihydroxypropyl)pteridinen: Kovalente intramolekulare Addukte

Pteridines: Synthesis and Characteristics of 5,6-Dihydro-6-(1,2,3-trihydroxypropyl)pteridines: Covalent Intramolecular Adducts Various 5,6-diaminopyrimidines ( 1, 15, 24, 33 ) were condensed with the phenylhydrazones of L -( 2 ) and D -arabinose ( 3 ) in acidic medium under N₂ to give formal 5,6-dihydro-6-(1,2,3-trihydroxypropyl)pteridines (see, e.g., 4 and 5 ), the latter turned out to exist preferentially as intramolecular adducts, the hexahydropyrano-3,2-g]pteridines 6, 7, 16, 17, 25, 26 , and 34 , formed subsequently by addition of the terminal OH group of the side-chain to the C(7)?N(8) bond of the pteridine moiety. Spectroscopically, the isomeric hexahydrofuro-3,2-g]pteridines 10,11,18,19 , and 35 were also detected as minor components in the equilibrium mixtures. In the 4-amino-2-(methylthio)pteridine series, crystallization of 6 and 7 led to the stereochemically pure (3S,4R,4aR, 10aS)-6-amino-3,4,4a,5,10,10a-hexahydro-8-(methylthio)-2H-pyrano3,2-g]pteridine-3,4-diol ( 8 ) and its corresponding enantiomer 9 , respectively Structure 8 was proven by X-ray analysis. Acylation of the hexahydropyrano3,2-g]pteridines yielded the more stable tri-, tetra-, and pentaacetyl derivatives 12–14, 20–23, 27–32 , and 37–39 which were characterized and of which the absolute and relative configurations were determined (¹H- and ¹³C–NMR and UV spectra, chiroptical measurements, elemental analyses).