Recent advances in synthetic and medicinal chemistry of phosphotyrosine and phosphonate-based phosphotyrosine analogues

Phosphotyrosine-containing compounds attract significant attention due to their potential to modulate signalling pathways by binding to phospho-writers, erasers and readers such as SH2 and PTB domain containing proteins. Phosphotyrosine derivatives provide useful chemical tools to study protein phosphorylation/dephosphorylation, and as such represent attractive starting points for the development of binding ligands and chemical probes to study biology, and for inhibitor and degrader drug design. To overcome enzymatic lability of the phosphate group, physiologically stable phosphonate-based phosphotyrosine analogues find utility in a wide range of applications. This review covers advances over the last decade in the design of phosphotyrosine and its phosphonate-based derivatives, highlights the improved and expanded synthetic toolbox, and illustrates applications in medicinal chemistry.

Photophysical characteristics of biologically active 4-aryloxymethyl coumarins 4PTMBC and 1IPMBC

The absorption and fluorescence characteristics of biologically active coumarin derivatives 4-p-tolyloxymethyl-benzo[h]coumarin (4PTMBC) and 1-(4-iodo phenoxymethyl)-benzo[f]coumarin (1IPMBC) are studied at room temperature in a series of organic solvents and 1,4-dioxane - acetonitrile solvent mixture. The effect of pure solvents on the spectral properties are analyzed using Lippert-Mataga polarity function, Reichardt's microscopic solvent polarity parameter, Kamlet's and Catalan's multiple linear regression approaches. Both general solute - solvent interactions and hydrogen bonding interactions are operative in these systems. However, the contribution of hydrogen bonding interactions is less compared to general solute-solvent interactions. The solvatochromic correlations are used to estimate excited state dipole moment using experimentally determined ground state dipole moment. The bathochromic shift of the emission spectra and the increase in excited state dipole moment indicate the intramolecular charge transfer (ICT) character in the emitting singlet state. The solvation studies in 1,4-dioxane - acetonitrile solvent mixture suggest that these dyes are preferentially solvated by 1,4-dioxane.

Spectral properties of binaphthalene-coumarins interconnected through hydrazone linkage

Photophysical properties of new coumarin-3-carbaldehyde (dihydrodinaphtho[2,1-c:1',2'-e]azepin-N-yl)imines bearing dimethylamino and methoxy groups at position 7 of coumarin were investigated. Dimethylamino derivative exhibits different solvent polarity dependence of fluorescent characteristics for nonpolar, medium polar and highly polar solvents. This effect can be rationalized by diverse charge distribution in the singlet excited state due to its different stabilization by solvation in the solvents of particular group. While 2-fold higher values of Stokes shift were observed for methoxy derivative, its quantum yield of fluorescence is much lower due to high nonradiative decay rate constant of the excited state.