Protecting group directed diversity during Mitsunobu cyclization of a carbohydrate derived diamino triol. Synthesis of novel bridged bicyclic and six-membered iminocyclitols.

A novel protecting group directed diversity leading to the synthesis of bridged bicyclic and six-membered iminocyclitols from a common carbohydrate derived diamino triol under Mitsunobu conditions is reported. When the intramolecular cyclization of benzoyl derivative 16 was carried out under Mitsunobu conditions, an unprecedented one-pot domino intramolecular "cyclization-N→O benzoyl migration-cyclization" reaction sequence occurred resulting in the formation of a chiral 2,6-diazabicyclo[3.2.1]octane-4,8-diol 21 in high yield. The structure of this novel bridged bicyclic compound was established through detailed NMR studies and single crystal X-ray analysis. On the other hand, the tert-butyldimethylsilyl derivative of the same substrate afforded protected 6-amino-1,6-dideoxy-l-gulonojirimycin 32 as the sole product under identical conditions. An attempt has been made to explain this difference in their reactivity through conformational analysis. The glycosidase inhibition studies of new compounds reported in this manuscript revealed that these molecules display moderate but selective inhibition against ß-N-acetylhexosaminidase.

Design and divergent synthesis of aza nucleosides from a chiral imino sugar.

Several novel nucleoside analogues as potential inhibitors of glycosidases and purine nucleoside phosphorylase (PNP) have been synthesized via selective coupling of an appropriate nucleobase at different positions of an orthogonally protected imino sugar as a common precursor. This synthetic strategy offers a straightforward protocol for the assembly of imino sugar containing nucleosides, establishing a new repertoire of molecules as potential therapeutics.

Quantum Dots as Biosensors in the Determination of Biochemical Parameters in Xenobiotic Exposure and Toxins.

Quantum dots (QDs) have been exploited for a range of scientific applications where the analytes can be expected to have significant photoluminescent properties. Previously, the applications of QDs as nanosensors for the detection of toxics in biospecimens, especially in cases of poisoning, have been discussed. This review focuses on the applications of QDs as biosensors for the detection of phytotoxins, vertebrate and invertebrate toxins, and microbial toxins present in biospecimens. Further, the role of QDs in the measurement of biochemical parameters of patient/victim as an indirect method of poison detection is also highlighted.

Design and synthesis of new amino-modified iminocyclitols: selective inhibitors of alpha-galactosidase.

A new and short synthesis of hitherto unreported stereo analogue of amino-modified five-membered iminocyclitols from readily available tri-O-benzyl-D-glucal is described. Significantly, glycosidase inhibition studies of alkylamino substituted iminocyclitols display a high degree of selectivity towards alpha-galactosidase.

Quantum dots as nanosensors for detection of toxics: a literature review.

Great advances have been made in sensor-based methods for chemical analysis owing to their high sensitivity, selectivity, less testing time, and minimal usage of chemical reagents. Quantum Dots (QDs) having excellent optical properties have been thoroughly explored for variety of scientific applications wherein light plays an important role. In recent years, there have been an increasing number of publications on the applications of QDs as photoluminescent nanosensors for the detection of chemicals and biomolecules. However, there has been hardly any publication describing the use of QDs in the detection of various toxic chemicals at one place. Hence, a literature survey has been made on the applications of QDs as chemosensors for the detection of gaseous, anionic, phenolic, metallic, drug-overdose, and pesticide poison so as to open a new perspective towards the role of sensors in analytical toxicology. In this review, the QD-based analysis of biospecimens for poison detection in clinical and forensic toxicology laboratories is highlighted.

Molecular basis for the affinity and specificity in the binding of five-membered iminocyclitols with glycosidases: an experimental and theoretical synergy.

An unusual substituent dictated complementarity in the inhibition of amino-modified five-membered iminocyclitols toward various glycosidases was reported by us. These intriguing results encouraged us to seek a molecular level explanation for the observation that may facilitate the design of specific iminocyclitol inhibitors against glycosidases of choice. We present here a detailed theoretical account that is substantiated with some new experimental investigations on the molecular origins of the differential affinities of iminocyclitols with various glycosidases. The studies involve docking/scoring, molecular dynamics simulations followed by syntheses of a few novel five-membered iminocyclitols and their in vitro binding assays. Directional hydrogen bonds and snug fit of the ligands are implicated as contributory to the observed selectivities. The observed synergy between the computations and experiment is likely to spur further research in the design of novel iminocyclitols with specific inhibitory activities.