Tyrosine maleic anhydride

Maleic acid is a linear four carbon molecule with carboxylate groups on both ends and a double bond between the central carbon atoms. The anhydride of maleic acid is a cyclic molecule containing five atoms. Although the reactivity of maleic anhydride is similar to other cyclic anhydrides, the products of maleylation are much more unstable toward hydrolysis, and the site of unsaturation lends itself to additional side reactions. Acylation products of amino groups with maleic anhydride are stable at neutral pH and above, but they readily hydrolyze at acid pH values around pH 3.5 (Butler et al., 1967). Maleylation of sulfhydryls and the phe-nolate of tyrosine are even more sensitive to hydrolysis. Thus, maleic anhydride is an excellent reversible blocker of amino groups to temporarily mask them from reactivity while another... 

A simple procedure to prepare 5-aryl- and 5-pyridyl-2-furaldehydes from inexpensive, commercially available 2-furaldehyde diethyl acetal was reported. The reaction proceeded in a four-step, one-pot procedure and the yield of coupling step was usually between 58-91% <02OL375>. A facile route to 3,4-furandicarboxylic acids was developed. DDQ-oxidation of 2,5-dihydrofuran derivatives, which were produced from dimethyl maleic anhydride, furnished the desired esters of furan-3,4-dicarboxylic acid <02S1010>. The furan-fused tetracyclic core of halenaquinol and halenaquinone possessing antibiotic, cardiotonic, and protein tyrosine kinase inhibitory activities was synthesized. Intramolecular cycloaddition of an o-quinodimethane with furan gave the adduct as a single isomer via an enrfo-transition state, which was converted to trisubstituted furan by oxidation-elimination reactions <02T6097>. 

Evidence was obtained for the presence of lysine side chains in active sites of rabbit antibodies directed to the p-azobenzoate, p-azobenzenearsonate, and p-azobenzenephosphonate groups (5). The minimum fractions of active sites containing lysine, in the three antibody populations, were 15, 45, and 25%, respectively. Maleic anhydride was used for the chemical modification. Conditions were chosen so as to minimize reactions with tyrosine, serine, and threonine. The values cited for percentages of active sites specifically modified were obtained from data on maximum hapten-binding capacity per molecule of antibody before and after treatment. Specific modification was taken as the difference between the numbers of sites inactivated in the presence of absence of a protective hapten. 

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