C-Glycopyranosyl aldehydes: emerging chiral synthons in organic synthesis

Herein, we have summarized the vast array of synthetic processes that have been developed for the synthesis of C-glycopyranosyl aldehydes and diverse C-glycoconjugates derived from them by covering the literature reported from 1979 to 2023. Notwithstanding its challenging chemistry, C-glycosides are considered stable pharmacophores and are used as important bioactive molecules. The discussed synthetic methodologies to access C-glycopyranosyl aldehydes take advantage of seven key intermediates, viz. allene, thiazole, dithiane, cyanide, alkene, and nitromethane. Furthermore, the integration of complex C-glycoconjugates derived from varied C-glycopyranosyl aldehydes involves nucleophilic addition/substitution, reduction, condensation, oxidation, cyclo condensation, coupling, and Wittig reactions. In this review, we have categorized the synthesis of C-glycopyranosyl aldehydes and C-glycoconjugates on the basis of the methodology used for their synthesis and on types of C-glycoconjugates, respectively.

A chemosensing approach for the colorimetric and spectroscopic detection of Cr3+, Cu2+, Fe3+, and Gd3+ metal ions

Metal cations are present in domestic and industrial wastewater and have adverse effects on human and aqueous life. The present study describes the development of the molecular probe 9-anthracen-9-ylmethylene)hydrazineylidene)methyl)-2,3,6,7-tetrahydro-1H,5H-pyrido[3,2,1-ij]quinolin-8-ol (AMHMPQ) to detect Cr³⁺, Cu²⁺, Fe³⁺, and Gd³⁺ ions by using UV-visible, fluorescence, colorimetric and excitation-emission matrix (EEM) spectroscopy techniques. The interaction of Cr³⁺, Cu²⁺, Fe³⁺, and Gd³⁺ can be observed by the absorption maxima shift, turn-off, colour changes, and EEM shifts. In addition, fluorescence limits of detection 17.66 × 10^-6 M, 6.44 × 10^-9 M, 28.87 × 10^-8 M, and 12.49 × 10^-6 M in wide linear ranges, low limits of quantifications, high values of Stern-Volmer constant, Job's plot and Benesi-Hildebrand plot justify the 1:1 association affinity with association constants of 1.46 × 10⁴ M^-1, 1.86 × 10⁷ M^-1, 2.69 × 10⁵ M^-1, 2.13 × 10⁴ M^-1 for AMHMPQ-metal ions (Cr³⁺, Cu²⁺, Fe³⁺, and Gd³⁺ ions), respectively. Paper- and mask-based kits are developed to explore the utility of the designed chemosensor. Additionally, AMHMPQ acts as a reusable sensor for two, seven, two, and zero cycles for Cr³⁺, Cu²⁺, Fe³⁺, and Gd³⁺ ions, respectively, when checked with EDTA.