Regioselective Synthesis of Dimethylamino- or Arylalkylamino-‘‘Crowned” Tröger's Base Analogues Under Vilsmeier-Haack Conditions

CuI-catalyzed amination of Tröger's base halides: a convenient method for synthesis of unsymmetrical Tröger's bases

A convenient and efficient Ullmann type copper catalyzed amination method has been developed for direct amination of halogen substituted Tröger's base analogues.

Design and synthesis of Tröger's base ditopic receptors: host-guest interactions, a combined theoretical and experimental study

Two flexible Tröger's base ditopic receptors C4TB and C5TB incorporating monoaza crown ether were designed and synthesized for bisammonium ion complexation. A comprehensive study of host-guest interactions was established by (1)H NMR spectroscopy and DFT calculations. Bisammonium chloride (A1) with a shorter alkyl chain spacer showed the highest affinity for the receptors. M06-2X/cc-pVTZ calculations including the solvent effects on host-guest complexes were employed to explain and rationalize the experimental trends. The short N-H···O or N-H···N hydrogen-bond distances observed in the range of 1.71-1.98 Å indicate the existence of a strong charge assisted hydrogen bonding between the host and the guest. The unusual behaviour (higher binding constant) of A5 in (1)H NMR titration is traced to the conformational folding of the guest.

Discovery of Tröger's base analogues as selective inhibitors against human breast cancer cell line: design, synthesis and cytotoxic evaluation

A library of structurally diverse Tröger's base analogues has been constructed via unusual amination of methylene bridge employing Vilsmeier-Haack conditions as well as by the incorporation of five and six membered heterocycles on the aromatic core of Tröger's base framework. The constructed structurally diverse frameworks were evaluated for their cytotoxic activities against a panel of three human cancer lines A549 (lung adenocarcinoma), MDAMB-231 (breast) and SK-N-SH (neuroblastoma). From the activity profile obtained, a redesign of Tröger's base analogues led to the construction of more potent molecular entities. The study led to development of a series of compounds with MDAMB-231 cell line specific cytotoxicity. Of the 30 compounds synthesized and evaluated, 7 compounds were found to possess cytotoxicity that is equivalent or better than standard drug doxorubicin against MDAMB-231 cell line while only one compound was found to be active against SK-N-SH cell line.

Readily accessible chiral at nitrogen cage structures

The reaction of glycine-N-methyl amide with paraformaldehyde in the presence of ytterbium triflate (1 mol%) leads to a novel cage structure 6 which is chiral at nitrogen. Single crystal X-ray analysis and DFT calculations suggest this cage structure is rigid and adopts a single low energy conformation. Use of single enantiomer α-amino amides results in two diastereomeric tertiary amines that differ in their absolute configuration at nitrogen. These diastereoisomers interconvert under acidic conditions but are configurationally stable under basic conditions and can be readily separated by either crystallisation or column chromatography. By reacting racemic chiral α-amino amides a third diastereomeric cage can also be isolated through this reaction protocol. Preparation of mixed cages by reacting two different α-amino amides is also possible allowing for greater structural diversity in the products to be attained. Preliminary mechanistic studies show that all three methylene units in the cage structure are labile and can be replaced under acidic reaction conditions.