Molecular and crystal structure of 5,6-diamino-1-methyluracil and 5,6-diamino-1,3-dimethyluracil monohydrate. Semiempirical calculations (AM1 and PM3) on 5,6-diaminouracil derivatives |
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| Institution: | 1. Departamento de Química Inorgánica & Orgánica, Facultad de Ciencias Experimentales, Universidad de Jaén, 23071 Jaén, Spain;2. Department of Applied Physics and Electronic & Manufacturing Engineering, University of Dundee, Dundee DD1 4HN, UK;1. Pharmaceutical Chemistry, School of Pharmacy, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa;2. Centre of Excellence for Pharmaceutical Sciences, School of Pharmacy, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa;1. Department of Chemistry Quaid-i-Azam University, 45320 Islamabad, Pakistan;3. Department of Chemistry, Bahauddin Zakariya University, Multan 60000, Pakistan;4. Department of Chemistry, Hazara University, Mansehra, Pakistan;1. University Institute of Pharmaceutical Sciences, Panjab University, Chandigarh 160014, India;2. Institut für Pharmakologie und Toxikologie, Universität Würzburg, Germany |
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| Abstract: | The crystal and molecular structures of 5,6-diamino-1-methyluracil and 5,6-diamino-1,3-dimethyluracil monohydrate have been determined from X-ray diffraction. Both compounds are planar and the two amino groups have two different conformations. The substituent at the 5 position seems to be a true primary amino group with a strongly sp3 nitrogen, whereas the one at the 6 position is nearly coplanar with the uracil ring, displaying a predominant sp2 character.Semiempirical calculations were made on 5,6-diaminouracil, 5,6-diamino-2-thiouracil and their endocyclic N-methylated derivatives using the AM1 and PM3 hamiltonians. These indicate that the stability decreases on increasing methylation, the 2-thio compounds always being less stable than the 2-oxo ones. |
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