Purines and related structures

A study of the coordination modes of organotin(IV) complexes with 6-thiopurine and related ligands has been published 05JOM1560 . 

Tautomerism in 5,8-diaza-7,9-dicarbaguanine (alloguanine) has been studied An X-ray structure analysis of the title compound revealed that this purinoid exists in the crystal as the two tautomers which interact with each other in the mode of a reverse-Watson-Crick base pair 05HCA1960 . 

The two tautomeric forms of one-electron oxidized guanosine have been investigated. The energetically most stable form is 68, the less stable form is 69 and its tautomerization to 68 has an activation energy of 23.0 kJ mol 05AG(E)6030 . 

A microwave assisted solid-phase synthesis of trisubstituted 2-(2,6-purin-9-yl)acetamides has been described 05TL2873 . New trisubstituted purin-8-ones 71 have been synthesized starting from cheap and readily available 5-bromouracil 70 05S2227 . 

Parallel synthesis of libraries of 2,6,8,9-tetrasubstituted purines have been reported, one proceeding via a sulfur intermediate 05JCC627 and another through the 2,8,9-trisubstituted 6-chloropurine core 05JCA474 . 

The number of publications under this heading is considerable, even through purine nucleosides and related structures have not been included. 

A general and efficient solid-phase synthesis of A-9-substituted 2,8-diamino purines 62 has been described. The key synthetic transformation uses a carbodiimide-mediated cyclization of a thiourea 60. The reaction was performed using microwave reaction conditions on solid phase 06TL8897 . 

A regiospecific strategy to A-7-substituted purines 65 and its application to a library of 2,6,8-trisubstituted purines has been reported. The three-step synthetic strategy involves cyclization reactions of suitably substituted pyrimidines 63 with either a carboxylic acid or an aldehyde 06JC0410 . 

A practical synthesis of 2-arylamino-6-alkylaminopurines from 2,6-dichloropurine by base-assisted substitution of the 6-chloro substituent with cyclobutylamine followed by a new trimethylsilyl chloride-catalyzed displacement of the 2-chloro group in the intermediate purine with an aromatic amine has been published 06OPRD799 . 

Suzuki-type Pd(0) coupling reactions have been used for the synthesis of 2-arylpurines 06BMCL3144 . 

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