DFT investigation of the regioselective allylation of pyrimidine 2'-deoxynucleosides.

To understand the regioselectivity observed in the allylation of pyrimidine nucleosides and to identify the factors directing the reaction, a theoretical study of the regioselective allylation was carried out. Several key points were considered such as: the structure of the deprotonated nucleobase in the presence of Na+; the effect of the solvent on the dissociation and aggregation reactions of thymidine/Na+ ion pair; and the likely allylation reaction mechanisms involved. The results showed that the regioselectivity observed experimentally can be attributed to a greater stability of a dimeric form coupled to an increase of the reaction barrier in THF due to larger Na+ binding to the nucleobase.

Synthesis and antitumor evaluation of novel sulfonylcycloureas derived from nitrogen mustard.

A new series of sulfonylcycloureas derivatives have been synthesized and evaluated in vitro for their antitumor activity against four cancer cell lines (A431, Jurkat, U266, and K562). These compounds were prepared by the condensation of several sulfonamides (2a-m) with ethyl bis(2-chloroethyl)carbamate (1a). The relative cytotoxicity of these new derivatives in comparison to chlorambucil is reported.

Pyrimidine-purine and pyrimidine heterodinucleosides synthesis containing a triazole linkage.

This article describes a synthetic route to generate two purine-pyrimidine and pyrimidine heterodinucleosides. Both microwave activated regioselective alkylation using hydride and copper-catalyzed-azide-alkyne-cycloaddition (CuAAC) were used in order to perform the synthesis.

Chelation-controlled regioselective alkylation of pyrimidine 2'-deoxynucleosides.

Protection-deprotection steps, which are usually needed for regioselective alkylation of pyrimidine deoxynucleosides, can be avoided by choosing the appropriate solvent. The combined effects of low dielectric constant and possible sodium chelation by pyrimidine nucleosides may account for the unexpected regioselectivity observed in THF.

Solvent-controlled regioselective protection of 5'-O-protected thymidine.

This paper describes an efficient procedure for selective 3'-O- or 3-N-protection of 5'-O-tert-butyldimethylsilylthymidine, depending on the use of aprotic polar solvents with low or high dielectric constant, respectively. These syntheses were activated by either ultrasound or microwaves. Several alkyl bromides offer a convenient route to prepare 3'-O- or 3-N-protected and functionalized thymidine derivatives.

Synthesis and biological evaluation of thioglycosylated porphyrins for an application in photodynamic therapy.

The aim of this work is the synthesis of a new family of glycosylated porphyrins in which the sugar moieties are linked to the tetrapyrrole ring by a thioglycosidic bond. Two series have been designed. The first one corresponds to meso-aryl porphyrin derivatives. The second one has been obtained from protoporphyrin IX derivatization. Aryl-porphyrins were prepared from tristolyl o- and p-hydroxyporphyrins followed by bromoallylation and thioglycosylation with peracetylated S-glucose, mannose and galactose and deprotection. The other series has been synthesized from protoporphyrin IX dimethylester with a regioselective glycosylation of terminal alkenyl carbon. The UV-visible, NMR and MALDI mass spectra are presented. Photocytotoxicities of the synthesized compounds against K562 chronic leukaemia cell line has been evaluated.