NDLI: Metal-promoted synthesis of amidines containing the model nucleobases 1-methylcytosine and 9-methyladenine

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Zangrando, Ennio Borsato, Giuseppe Montagner, Diego Longato, Bruno Lucchini, Vittorio
Description	Author Affiliation: Montagner D ( Dipartimento di Scienze Chimiche, Università di Padova, Via Marzolo 1, 35131, Padova, Italy. diego.montagner@unipd.it)
Abstract	The amidine complexes $cis-[L_{2}PtNH=C(R)\{1-MeCy(-2H)\}]NO_{3}$ (R = Me, 1a; Ph, 1b, $Me_{3}C,$ 1c; $Ph_{2}(H)C,$ 1d) and $cis-[L_{2}PtNH=C(R)\{9-MeAd(-2H)\}]NO_{3}$ (R = Me, 2a; Ph, 2b; $Me_{3}C,$ 2c; $Ph_{2}(H)C,$ 2d), are formed when $cis-[L_{2}Pt(μ-OH)]_{2}(NO_{3})_{2}$ (L = $PPh_{3})$ reacts with 1-methylcytosine (1-MeCy) and 9-methyladenine (9-MeAd) in solution of MeCN, PhCN, $Me_{3}CCN$ and $Ph_{2}(H)CCN.$ Reaction of 1a,b and 2a,b with HCl affords the protonated amidines $[NH_{2}=C(R)\{1-MeCy(-H)\}]NO_{3}$ (R = Me, 3a; Ph, 3b) and $[NH_{2}=C(R)\{9-MeAd(-H)\}]NO_{3}$ (R = Me, 4a; Ph, 4b) and $cis-(PPh_{3})_{2}PtCl_{2}$ in quantitative yield. Treatment of 3b and 4b with NaOH allows the isolation of the neutral benzimidamides $NH_{2}-C(Ph)\{1-MeCy(-2H)\}$ (5b) and $NH_{2}-C(Ph)\{9-MeAd(-2H)\}$ (6b). In the solid state 3b shows a planar structure with the hydrogen atom on N(4) cytosine position involved in a strong H-bond with the $NO_{3}^{−}$ ion. Intermolecular H-bonds between the oxygen of the cytosine ring and one of the H atoms of the $amidine-NH_{2}$ group allow the dimerization of the molecule. A detailed analysis of the spectra of 3b in $DMF-d_{7}$ at −55 °C indicates the presence of an equilibrium between the species $[NH_{2}=C(R)\{1-MeCy(-H)\}]NO_{3}$ and $[NH_{2}=C(R)\{1-MeCy(-H)\}]_{2}(NO_{3})_{2},$ exchanging with trace amounts of water at 25 °C. $[^{15}N,^{1}H]-HMBC$ experiments for 5b and 6b indicate that the amino tautomer $H_{2}N-C(Ph)\{nucleobase(-2H)\},$ is the only detectable in solution and such structure has been confirmed in the solid state. The reaction of 5b and 6b with $cis-L_{2}Pt(ONO_{2})_{2}$ (L = $PPh_{3}),$ in chlorinated solvents , determines the immediate appearance of a pale yellow colour due to the coordination of the neutral amidine , likely in its imino form HN=C(Ph){nucleobase(-H)}, to give the adducts $cis-[L_{2}PtNH=C(Ph)\{nucleobase(-H)\}]^{2+}.$ In fact, addition of “ proton sponge ” leads to the immediate deprotonation of the amidine ligand with formation of the starting complexes 1b and 2b.
ISSN	14779226
Issue Number	34
Volume Number	40
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2011-09-14
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Adenine Analogs & Derivatives Amidines Chemical Synthesis Cytosine Metals Chemistry Organic Chemistry Phenomena Journal Article Research Support, Non-U.S. Gov't
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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