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Metal‐Modified Nucleobase Sextet: Joining Four Linear Metal Fragments ( trans ‐a 2 Pt II ) and Six Model Nucleobases to an Exceedingly Stable Entity
Author(s) -
Sigel Roland K. O.,
Thompson Susan M.,
Freisinger Eva,
Glahé Frank,
Lippert Bernhard
Publication year - 2001
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20010504)7:9<1968::aid-chem1968>3.0.co;2-b
Subject(s) - nucleobase , guanine , chemistry , stereochemistry , ligand (biochemistry) , metal , crystallography , base pair , uracil , dna , organic chemistry , nucleotide , biochemistry , receptor , gene
Crosslinking of three different model nucleobases (9‐ethyladenine, 9‐EtA; 9‐ethylguanine, 9‐EtGH; 1‐methyluracil, 1‐MeU) by two linear trans ‐a 2 Pt II (a= NH 3 or CH 3 NH 2 ) entities leads to a flat metal‐modified base triplet, trans , trans ‐[(NH 3 ) 2 Pt(1‐MeU‐ N 3)( μ ‐9‐EtA‐ N 7, N 1)Pt(CH 3 NH 2 ) 2 (9‐EtGH‐ N 7)] 3+ ( 4 b ). Upon hemideprotonation of the 9‐ethylguanine base at the N1 position, 4 b spontaneously dimerizes to the metalated nucleobase sextet 5 , [( 4 b )≡( 4 b ‐H)] 5+ . In this dimeric structure a neutral and an anionic guanine ligand, which are complementary to each other, are joined through three H bonds and additionally by two H bonds between guanine and uracil nucleobases. Four additional interbase H bonds maintain the approximate coplanarity of all six bases. The two base triplets form an exceedingly stable entity ( K D =500±150 M −1 in DMSO), which is unprecedented in nucleobase chemistry. The precursor of 4 b and several related complexes are described and their structures and solution properties are reported.