Purines Fused with Five-Membered Heterocycles

Purines Fused with Five-Membered Heterocycles 

A representative of this group, 3,6,7,8-tetrahydro-4-oxo-4//-pyrrolo[l, 2-e]-purine-8-carboxylic acid and various derivatives were obtained from ethyl 5-ethoxy-3,4-diliv dro-2//-pyrrole-2-carboxylate (10) and amino-cyanoacetamide (11) in ethanolic 

Displacement of bromine by benzhydrylpiperazine in 8-(3-bromopropyl)-1,3-dimethyl- or l-isobutyl-3-methyl-3,7-dihydro-l/7-purine-2,6-diones gave rise to the required product and small amounts of 1,3-dimethyl- or l-isobutyl-3-methyl-l,6,7,8-tetrahydro-2/7-pyrrolo[l,2-e]-purine-2,4(3/7)-dione and its [2,1-/] position isomer. The structures of both substances were corroborated by H-NMR spectra (87EJM243). 

The second method was based on a cycloaddition reaction of olefinic and acetylenic dipolarophiles to xanthinium-(N7) ylides. Xanthinium-(N7) ylides 22 were generated from 7-substituted 1,3,9-trimethylxanthinium tosylates 21 by deprotonation with triethylamine in dry acetonitrile followed by reaction with dipolarophiles 23 and 25 (dimethyl fumarate, fumaronitrile, methyl acrylate, acrylonitrile and the like). Reaction with dimethyl fumarate afforded the endo-(24a) and exo-(24b) adducts in a 3 2 ratio. The stereochemistry of these compounds was established by H-NMR and X-ray analysis (84H2199). With derivatives of acrylic acid 25, only endo adducts (26) 

33 reacted with other nucleophiles to form 4-methoxy-, 4-benzylamino-, and 4-morpholino derivatives. Alkylation of the Na+ or K+ salt of 4-mercapto derivative 

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II. Purines Fused with Five-Membered Heterocycles. 86... 

Purines with a Fused Heterocyclic Ring System 7.11.7.5.1 Five-membered fused rings... 

This review presents purines annulated with fused five-membered rings, as pyrrolo-, oxazolo-, thiazolo-, imidazo-, pyrazolo-, triazolo-, and tetrazolo-purines. Aiming to eliminate some misinterpretations (numbering of the skeleton in some papers did not match those in Chemical abstracts) atoms of the first scheme in each chapter will be numbered. Each group of compounds includes the synthesis, reactions of the heterocyclic system in question, biological effects, and, if accessible, also references about the detailed spectral data, X-ray analysis and so on. Papers were abstracted up to December 2002, inclusive vol. 137 of Chemical Abstracts. 

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