Naslov
Atropisomerism and spontaneous resolution of N-sulfonylpyrimidine derivatives

Autori
Višnjevac, Aleksandar ; Luić, Marija ; Žinić, Mladen ; Žinić, Biserka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
13th Slovenian-Croatian Crystllographic Meeting : Book of Abstracts and Programme / Golič, Ljubo - Ljubljana : Univerza v Ljubljani, 2004, 51-51

Skup
13th Slovenian-Croatian Crystallographic Meeting

Mjesto i datum
Bovec, Slovenija, 16.06.2004. - 20.06.2004

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Nije recenziran

Ključne riječi
sulfonylpyrimidine; atropisomerism; spontaneous resolution; conformational chirality

Sažetak
Formation of chiral crystals of a compound without any stereogenic element is rare and of great interest in the field of absolute asymmetric synthesis in the solid state, as well as in connection with the origin of homochirality of life.[1] The title compounds belong to a novel series of pyrimidine nucleobase derivatives possessing a sulfonamide pharmacophore. Some of them exhibit significant anticancer activity in vitro.[2] As a part of the overall structural examination, the crystal structures of 1-tosylthymine (1), 1-tosyluracil (2) and 1-(1-naphthylsulfonyl)uracil (3) are presented. These compounds crystallise in orthorhombic system (1 in Pbca, 2 and 3 in P212121), whereby the cell volume of 1 is twice as large as the one of 2 (doubling of one axis). The axial conformational chirality was encountered in all compounds, as a consequence of the S1-N1 single bond free rotation hindrance in solid state (atropisomerism). [3] The spontaneous resolution of Ra and Sa enantiomers occured only during the crystallisation of 2 and 3, whereas 1 crystallised as a racemate. In the case of 2, the recemically twinned crystals with cca 70% of one and 30% of the other enantiomer present, were obtained by the slow evaporation of both methanol and acetonytrile solutions, whereas only the Sa enantiomer crystallised in the case of 3. The NMR data for 1 and 2 confirmed the low energy barier for the free rotation of the S-N bond in the solution. The SHELXL merohedral twin refinement was applied in the case of the racemically twinned species (2), and the resulting Flack parameter was discussed. The interdependence of the crystal packing and the occurence of the spontaneous resolution were discussed, bearing in mind chemical differences between the observed compounds.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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