Abkömmlinge der 1,7,9‐Trimethylharnsäure

Biltz, Heinrich; Krzikalla, Hans

doi:10.1002/jlac.19214230206

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1997

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Cited by 4 publications

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The Oxo‐(Hydroxy‐) and Alkoxypurines

1971

Chemistry of Heterocyclic Compounds: A Series of Monographs

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The Oxo‐(Hydroxy‐) and Alkoxypurines

1971

Chemistry of Heterocyclic Compounds: A Series of Monographs

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Conformational and stereoelectronic control in ring‐transformations of cis‐4,5‐dialkoxytetrahydropurine‐2,6,8‐triones

Poje¹,

Palković²,

Poje³

1997

Journal of Heterocyclic Chem

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Divergent acid‐catalysed ring‐openings of 4,5‐dimethoxytetrahydropurine‐2,6,8‐triones 2 at position 4, yielding 1‐(5‐methoxyhydantoin‐5‐carbonyl)ureas 4 (R7 = Me) or 5‐methoxy‐5‐ureido‐2,4,6‐pyrimidinetriones 5 (R7 = H), can be rationalized by assuming a preference for one of two conformational isomers of the cis‐fused system, associated with the N‐substitution effects. Intramolecular transamidation 5 → 4 presumably occurs via a bicyclic acid aminal type intermediate 3, heretofore misassigned as the reaction product. A curious base‐catalysed rearrangement was encountered with the 5 (R1 = R3 = Me, R7 = H) cases, which afforded 5‐methoxy‐1,5‐bis(methylaminocarbonyl)hydantoins 7. Remarkable stability of the conformationally rigid propellane type 4,5‐ethylenedioxytetrahydropurine‐2,6,8‐triones 9 toward acids, shows that the mode of ring‐opening at position 4 is controlled by powerful Stereoelectronic factors. However, an alternative ring‐opening at the 1,6‐bond has occurred on heating aqueous solutions of 9a (R7 = H); the ensuing decarboxylative rearrangement leads to 1,3‐dimethylallantoin (12) and its precursor, 1‐(2‐hydroxyethoxy)‐2,4‐dimethyl‐3,7‐dioxo‐2,4,6,8‐tetraazabicyclo[3.3.0]octane(11).

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