I. Use of 9-methylfluorene as an indicator for organometallic titrations II. Synthesis of a branched polyethylene glycol linker for peptide ligands III. Synthesis of a linker for peptide ligands and a study of its pH sensitivity

Abstract

This work details the synthesis of some useful organic molecules: (I) 9-Methylfluorene was tested as an indicator in the titration of commonly used organometallic reagents. This indicator is readily prepared in three steps from fluorenone. In THF solution the deprotonated indicator is red and exhibits a sharp endpoint. The highly basic reagents sec-butyllithium and tert -butyllithium can be titrated in ether solution, where the color of the deprotonated indicator is yellow. (II) A branched, polyethylene glycol based linker for peptide ligands was designed and synthesized. The linker needed to be water soluble, to be stable under both acidic and basic conditions, to have amine and carboxyl termini for use in solid phase peptide synthesis, and to have an attachment site for a fluorescent marker. The polyethylene glycol linker was designed with a carboxyl terminus and two amine termini that can be differentially protected to facilitate selective deprotection and reaction with three peptides or two peptides and a fluorescent tag. (III) A molecule containing a linear polyethylene glycol linker with beta-alkoxyamide moiety was synthesized and its pH stability determined using an HPLC method. Stability was assayed in 5 mM buffers at pH 4, 7, and 9 over 24 hours. No decomposition in these solutions was detected. The linker was then subjected to 10 mM acid or base solution and analyzed over 24 hours. Again, no decomposition was observed.