Isothiocyanates functional derivatives

In the literature, fluorescence spectroscopy in OFD has been limited to the use of ultraviolet (UV) or visible dyes as molecular probes.(1) The most common fluorescent dye used in OFD is fluorescein and its derivatives/21 23) Fluorescein possesses a good fluorescence quantum yield and is commercially available with an isothiocyanate functionality for linking to the polymeric support/24-26 Additionally, selective laser excitation can be performed because the absorbance maximum of fluorescein coincides with the 499-nm laser line emitted from an argon laser. Unfortunately, argon lasers are costly and bulky, thus limiting the practicality of their use. Similar difficulties exist with other popular commercial dyes. 

Reaction of />-phenylene diisothiocyanate 188 with 7-thiobutyrolactone in an alkaline medium yields a 4-thiocarba-moylthiobutyric acid derivative after acidification. This is cyclized to the 2-thioxo-l,3-thiazepan-4-one derivative 189. The remaining isothiocyanate functionality is subjected to a [2+2] cycloaddition with iVjiV -dicyclohexylcarbo-diimide (DCC) forming a 1,3-thiazetidine system 190 where both isothiocyanate groups have reacted (Scheme 61) <1999JHC1167>. 

The reaction of monosaccharide isothiocyanates with enamines leads to the formation of a./J-u maturated thioamides4,169 (67), which can be cy-clized to isothiazole derivatives.4 Formation of additional products arising from attack of the amino group to the isothiocyanate functionality has also been observed, the outcome of the reaction being dependent on the nature of the enamine reagent and on reaction conditions. Thus, nucleophilic addition of a series of 3-amino-3-penten-2-ones (65) and ethyl 3-aminocroto-... 

Several reactive isothiocyanates undergo dimerization reactions in which one of the isothiocyanates functions as the diene and the other isothiocyanate reacts as the dienophile. These [4-1-2] cycloaddition reactions are very pronounced with heterocyclic isothiocyanates and isothiocyanates having carbonyl, thiocarbonyl and imidoyl substituents. For example, 2-pyridyl isothiocyanate undergoes dimerization to give the triazine derivative 2. ... 

In those cases where quantities of the test organisms are limited or non-aqueous conditions are preferred, blending of the lyophilized sponge with organic solvents is employed. The latter option is prudent, if one suspects the presence of reactive isocyano and isothiocyano functions. Although these isolation methods may not be unduly harsh, artifacts derived from isonitriles and isothiocyanates may arise. 

The conversion of acyl isothiocyanates 47 with sodium azide leads to thiol-functionalized tetrazole derivatives such as 48 (Scheme 9) <1995PJC1022>. The reaction of 48 with chloro acetonitrile leads to an intermediate 49 that reacts in... 

Extending the utility of fluorescence to various nonfluorophores is achieved via chemical derivatization methods, also termed labeling or tagging methods (Reaction 11.2). Numerous commercial fluorescent tags are available with disparate reactive functional groups. For example, derivatives of fluorescein, fluorescein isothiocyanate (FITC) are reactive toward nucleophiles such as amines and sulfhydryl groups. 

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