Fluorescent Labeling of a Target Protein with an Alkyl Diazirine Photocrosslinker Bearing a Cinnamate Moiety.

A novel fluorogenic alkyl diazirine photocrosslinker bearing an o-hydroxycinnamate moiety has been developed for identification of the targets of bioactive molecules. The o-hydroxycinnamate moiety can be converted to the corresponding 7-hydroxycoumarin derivative, which should be created on the interacting site within the photocaptured target protein. The label yield and fluorescence intensity have been immensely improved in comparison with our previous aromatic crosslinkers to facilitate target identification in small quantities.

Amphos-Mediated Conversion of Alkyl Azides to Diazo Compounds and One-Pot Azide-Site Selective Transient Protection, Click Conjugation, and Deprotective Transformation.

A one-pot conversion of alkyl azides to diazo compounds is outlined. After the reaction of α-azidocarbonyl compounds with Amphos, treatment of the resulting phosphazides with silica gel in a wet solvent afforded α-diazo carbonyl products. Through the azido group protection property of Amphos, inter- and intramolecular azide-site selective reactions of azido group protection, click functionalization, and deprotection of the diazo group have been demonstrated in one pot.

Synthesis of Naphthalimide Azocarboxylates Showing Turn-On Fluorescence by Substitution Reaction with Sulfinates.

The synthesis and characterization of sulfinate addition-responsive fluorescent molecules are described. We found that addition reaction of sulfinates to naphthalimide-substituted azocarboxylates afforded the corresponding sulfonyl hydrazides with high fluorescence quantum yields (up to 0.91 in THF and 0.54 in methanol), which exhibited a large Stokes shift (105 nm) in protic methanol solvent, while the unsubstituted hydrazide and the sulfonyl-position isomer showed no fluorescence in polar solvents.