Siderophores are unique ferric ion chelators produced and secreted by some organisms like bacteria, fungi and plants under iron deficiency conditions. These molecules possess immense affinity and specificity for Fe3+ and other metal ions, which attracts great interest due to the numerous possibilities of application, including antibiotics delivery to resistant bacteria strains. Total synthesis of siderophores is a must since the compounds are present in natural sources at extremely small concentrations. These molecules are extremely diverse in terms of molecular structure and physical and chemical properties. This review is focused on achievements and developments in the total synthesis strategies of naturally occurring siderophores bearing arylthiazoline and aryloxazoline units.
A series of chiral sulfonamides containing the 2-azabicycloalkane scaffold were prepared from aza-Diels–Alder cycloadducts through their conversion to amines based on 2-azanorbornane or the bridged azepane skeleton, followed by the reaction with sulfonyl chlorides. The cytotoxic activity of the obtained bicyclic derivatives was evaluated using human hepatocellular carcinoma (HCC), medulloblastoma (MB), and glioblastoma (GBM) cell lines. Chosen compounds were shown to notably reduce cell viability as compared to nonmalignant cells.
In a search for new, selective antitumor agents, we prepared a series of sulfonamides built on bicyclic scaffolds of 2-azabicyclo(2.2.1)heptane and 2-azabicyclo(3.2.1)octane. To this end, aza-Diels–Alder cycloadducts were converted into amines bearing 2-azanorbornane or a bridged azepane skeleton; their treatment with sulfonyl chlorides containing biaryl moieties led to the title compounds. The study of antiproliferative activity of the new agents showed that some of them inhibited the growth of chosen cell lines with the IC50 values comparable with cisplatin, and some derivatives were found considerably less toxic for nonmalignant cells.
This paper describes the synthesis of chiral diselenides based on 2-azabicycloalkane or the pyrrolidine skeleton using in situ generated Na2Se2 as an efficient selenylating reagent. All the diselenides were obtained in moderate yields under mild conditions. The well-defined enantio- and diastereomerically pure compounds were tested in the asymmetric alkoxyselenylation of alkenes yielding products with diastereoisomeric excess up to >99%.
Carbon–carbon bond forming reactions, such as aldol reaction and condensation, belong to extremely desired transformations as manifested by >25,000 entries in SciFinder. Their stereoselective variant requires the use of an appropriate catalyst with a strictly defined structure. Hence, chiral 2-azabicycloalkane-based catalysts were designed, synthesized and tested in a stereoselective aldol reaction between cyclic/acyclic ketone and p-nitrobenzaldehyde both in organic and aqueous media. Among catalysts containing a chiral bicyclic backbone, amide based on 2-azabicyclo[3.2.1]octane and pyrrolidine units showed the best catalytic activity and afforded aldol product in excellent chemical yields (up to 95%) and good diastereo- and enantioselectivity (dr 22:78, ee up to 63%).