Metal-Modified Nucleobase Sextet: Joining Four Linear Metal Fragments (trans-a2PtII) and Six Model Nucleobases to an Exceedingly Stable Entity

Crosslinking of three different model nucleobases (9‐ethyladenine, 9‐EtA; 9‐ethylguanine, 9‐EtGH; 1‐methyluracil, 1‐MeU) by two linear trans‐a2PtII (a= NH3 or CH3NH2) entities leads to a flat metal‐modified base triplet, trans,trans‐[(NH3)2Pt(1‐MeU‐N3)(μ‐9‐EtA‐N7,N1)Pt(CH3NH2)2(9‐EtGH‐N7)]3+ (4 b)....

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Bibliographic Details
Published in:Chemistry : a European journal 2001-05, Vol.7 (9), p.1968-1980
Main Authors: Sigel, Roland K. O., Thompson, Susan M., Freisinger, Eva, Glahé, Frank, Lippert, Bernhard
Format: Article
Language:English
Subjects:
Base Pairing
Cisplatin - chemistry
Crystallography, X-Ray
hydrogen bonds
Magnetic Resonance Spectroscopy
molecular recognition
Molecular Structure
Nucleic Acid Precursors - chemistry
nucleobases
Organoplatinum Compounds - chemical synthesis
Platinum
Purines - chemistry
Pyrimidines - chemistry
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Summary:Crosslinking of three different model nucleobases (9‐ethyladenine, 9‐EtA; 9‐ethylguanine, 9‐EtGH; 1‐methyluracil, 1‐MeU) by two linear trans‐a2PtII (a= NH3 or CH3NH2) entities leads to a flat metal‐modified base triplet, trans,trans‐[(NH3)2Pt(1‐MeU‐N3)(μ‐9‐EtA‐N7,N1)Pt(CH3NH2)2(9‐EtGH‐N7)]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 (KD=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. Die Verknüpfung dreier unterschiedlicher Modellnucleobasen (9‐Ethyladenin, 9‐EtA; 9‐Ethylguanin, 9‐EtGH; 1‐Methyluracilat, 1‐MeU) über zwei lineare trans‐a2PtII‐Einheiten (a=NH3 oder CH3NH2) führt zu einem flachen metall‐modifizierten Basentriplett, trans,trans‐[(NH3)2Pt(1‐MeU‐N3)(μ‐9EtA‐N7,N1)Pt(CH3NH2)2(9‐EtGH‐N7)]3+ (4 b). 4 b dimerisiert im Falle einer Hemi‐Deprotonierung der Guanin‐N1 Position spontan zu einem Nucleobasen‐Sextett 5, [(4 b)≡(4 b‐H)]5+. Die beiden Triplett Strukturen werden hierbei über 3 H‐Brücken zwischen den komplementären Guaninbasen sowie über zwei H‐Brücken zwischen jeweils einem Guanin‐ und einem Uracilliganden verknüpft. Vier weitere H‐Brücken zwischen Guanin und Adenin sowie zwischen Adenin und Uracil führen zu annähernder Coplanarität aller sechs Basen. Die Komplexbildung der beiden Basentripletts ist mit KD=500±150 M−1 (DMSO) so hoch wie in keinem anderen bekannten Nucleobasenassoziat. Im folgenden werden ferner die Strukturen und das Lösungsverhalten der Vorstufe von 4 b sowie mehrer verwandter Verbindungen diskutiert. Hemideprotonation of the guanine ligand in a diplatinated nucleobase triplet leads to self‐association and the formation of an exceedingly stable nucleobase sextet structure both in solution and in the solid state (see picture).
ISSN:0947-6539
1521-3765
DOI:10.1002/1521-3765(20010504)7:9<1968::AID-CHEM1968>3.0.CO;2-B