On the electron withdrawing nature of ethers in glycosylation chemistry.

The present paper is a commentary on the electronic effects that protecting groups exert on glycosylation chemistry. Specifically, its purpose is to rectify the misguided use of the term electron donating benzyl groups, which hardly makes sense in the context of protecting groups on alcohols in saturated systems such as carbohydrates. It is argued that benzyl ethers (OBn) should rightfully be referred to as being inductively electron withdrawing, even if they are less so than benzoyl esters (OBz).

Combining Click Reactions for the One-Pot Synthesis of Modular Biomolecule Mimetics.

Here, we report on the first combined one-pot use of the two so-called "click reactions": the thiol-ene coupling and the copper-catalyzed alkyne-azide cycloaddition. These reactions were employed in an alternating and one-pot fashion to combine appropriately functionalized monomeric carbohydrate building blocks to create mimics of trisaccharides and tetrasaccharides as single anomers, with only minimal purification necessary. The deprotected oligosaccharide mimics were found to bind both plant lectins and human galectin-3.

Divergent synthesis of new α-glucosidase inhibitors obtained through a vinyl Grignard-mediated carbocyclisation.

Four new α-glucosidase inhibitors have been synthesised through 5-8 synthetic steps from a common synthetic intermediate obtained through a recently developed carbocyclisation. The compounds were designed as hybrids of the known glucosidase inhibitors valienamine, voglibose and miglitol. All four compounds showed activity against rat intestinal sucrase with the most potent inhibitor acting at low micromolar concentration. The newly synthesised compounds were not as potent as miglitol against sucrase but showed greater selectivity towards the tested glycosidases. The most potent inhibitors were docked into a homology model built for this study of rat intestinal sucrase explaining the difference in potency between two diastereoisomers with varying orientation of a secondary amine.

Synthesis and inhibitory evaluation of 3-linked imipramines for the exploration of the S2 site of the human serotonin transporter.

The human serotonin transporter is the primary target of several antidepressant drugs, and the importance of a primary, high affinity binding site (S1) for antidepressant binding is well documented. The existence of a lower affinity, secondary binding site (S2) has, however, been debated. Herein we report the synthesis of 3-position coupled imipramine ligands from clomipramine using a copper free Sonogashira reaction. Ligand design was inspired by results from docking and steered molecular dynamics simulations, and the ligands were utilized in a structure-activity relationship study of the positional relationship between the S1 and S2 sites. The computer simulations suggested that the S2 site does indeed exist although with lower affinity for imipramine than observed within the S1 site. Additionally, it was possible to dock the 3-linked imipramine analogs into positions which occupy the S1 and the S2 site simultaneously. The structure activity relationship study showed that the shortest ligands were the most potent, and mutations enlarging the proposed S2 site were found to affect the larger ligands positively, while the smaller ligands were mostly unaffected.

Analysis of JmjC Demethylase-Catalyzed Demethylation Using Geometrically-Constrained Lysine Analogues.

The dynamic post-translational modifications of histones play important roles in the regulation of transcription in animals. The demethylation of N(ε)-methyl lysine residues in the N-terminal tail of histone H3 is catalyzed by demethylases, of which the largest family is the ferrous iron and 2-oxoglutarate dependent demethylases (JmjC KDMs), which catalyze demethylation via initial hydroxylation of the N-methyl groups. We report studies on the conformational requirements of the JmjC KDM substrates using N-methylated lysine analogues prepared by metathesis reactions of suitably protected N-allylglycine. The results support the proposed requirement for a positively charged N(ε)-amino group in JmjC KDM catalysis. Demethylation of a trans-C-4/C-5 dehydrolysine substrate analogue was observed with representative KDM4 subfamily members KDM4A, KDM4B and KDM4E, and KDM7B, which are predicted, based on crystallographic analyses, to bind the N(ε)-methylated lysine residue in different conformations during catalysis. This information may be useful in the design of JmjC KDM selective inhibitors.

Basic N-interlinked imipramines show apoptotic activity against malignant cells including Burkitt's lymphoma.

We here report the synthesis of ethylene glycol N-interlinked imipramine dimers of various lengths from the tricyclic antidepressant desipramine via an amide coupling reaction followed by reduction with lithium aluminium hydride. The target molecules were found to be potent inhibitors of cellular viability while inducing cell type specific death mechanisms in three cancer cell lines including a highly chemoresistant Burkitt's lymphoma cell line. Basic amine analogues were found to be important for increased potency. Imipramine and desipramine were also tested for apoptotic activity and were found to be much less active than the novel dimeric compounds. Imipramine dimers were only found to be moderate inhibitors of the human serotonin transporter (hSERT) having IC(50) values in the micromolar region whilst the induction of cell death occurred independently of hSERT expression. These results demonstrate the potential of newly designed and synthesised imipramines derivatives for use against malignant cells, including those resistant to standard chemotherapy.