ortho-Carborane-ModifiedN-Substituted Deoxynojirimycins

Carboranes in drug discovery, chemical biology and molecular imaging

There exists a paucity of structural innovation and limited molecular diversity associated with molecular frameworks in drug discovery and biomolecular imaging/chemical probe design. The discovery and exploitation of new molecular entities for medical and biological applications will necessarily involve voyaging into previously unexplored regions of chemical space. Boron clusters, notably the carboranes, offer an alternative to conventional (poly)cyclic organic frameworks that may address some of the limitations associated with the use of novel molecular frameworks in chemical biology or medicine. The high thermal stability, unique 3D structure and aromaticity, kinetic inertness to metabolism and ability to engage in unusual types of intermolecular interactions, such as dihydrogen bonds, with biological receptors make carboranes exquisite frameworks in the design of probes for chemical biology, novel drug candidates and biomolecular imaging agents. This Review highlights the key developments of carborane derivatives made over the last decade as new design tools in medicinal chemistry and chemical biology, showcasing the versatility of this unique family of boron compounds.

Synthesis and glycosidase inhibition of 5-C-alkyl-DNJ and 5-C-alkyl-l-ido-DNJ derivatives

5-C-Alkyl-DNJ and 5-C-alkyl-l-ido-DNJ derivatives have been designed and synthesized efficiently from an l-sorbose-derived cyclic nitrone. The DNJ and l-ido-DNJ derivatives with C-5 alkyl chains ranging from methyl to dodecyl were assayed against various glycosidases to study the effect of chain length on enzyme inhibition. Glycosidase inhibition study of DNJ derivatives showed potent and selective inhibitions of α-glucosidase; DNJ derivatives with methyl, pentyl to octyl, undecyl and dodecyl as C-5 branched chains showed significantly improved rat intestinal maltase inhibition. In contrast, most 5-C-alkyl-l-ido-DNJ derivatives were weak or moderate inhibitors of the enzymes tested, with only three compounds found to be potent α-glucosidase inhibitors. Docking studies showed different interaction modes of 5-C-ethyl-DNJ and 5-C-octyl-DNJ with ntMGAM and also different binding modes of 5-C-alkyl-DNJ and 5-C-alkyl-l-ido-DNJ derivatives; the importance of the degree of accommodation of the C-5 substituent in the hydrophobic groove and pocket may account for the variation of glycosidase inhibition in the two series of derivatives. The results reported herein are helpful in the design and development of α-glucosidase inhibitors; this may lead to novel agents for the treatment of viral infection and type II diabetes.

N-Alkylated Iminosugar Based Ligands: Synthesis and Inhibition of Human Lysosomal β-Glucocerebrosidase

The scope of a series of N-alkylated iminosugar based inhibitors in the d-gluco as well as d-xylo configuration towards their interaction with human lysosomal β-glucocerebrosidase has been evaluated. A versatile synthetic toolbox has been developed for the synthesis of N-alkylated iminosugar scaffolds conjugated to a variety of terminal groups via a benzoic acid ester linker. The terminal groups such as nitrile, azide, alkyne, nonafluoro-tert-butyl and amino substituents enable follow-up chemistry as well as visualisation experiments. All compounds showed promising inhibitory properties as well as selectivities for β-glucosidases, some exhibiting activities in the low nanomolar range for β-glucocerebrosidase.

New keys for old locks: carborane-containing drugs as platforms for mechanism-based therapies

Icosahedral carboranes in medicine are still an emerging class of compounds with potential beneficial applications in drug design. These highly hydrophobic clusters are potential "new keys for old locks" which open up an exciting field of research for well-known, but challenging important therapeutic substrates, as demonstrated by the numerous examples discussed in this review.