1.Use of site-directed chemical modification to study an essential lysine in Escherichia coli leader peptidase.
Paetzel M1, Strynadka NC, Tschantz WR, Casareno R, Bullinger PR, Dalbey RE. J Biol Chem. 1997 Apr 11;272(15):9994-10003.
Escherichia coli leader peptidase, which catalyzes the cleavage of signal peptides from pre-proteins, is an essential, integral membrane serine peptidase that has its active site residing in the periplasmic space. It contains a conserved lysine residue that has been proposed to act as the general base, abstracting the proton from the side chain hydroxyl group of the nucleophilic serine 90. To help elucidate the role of the essential lysine 145 in the activity of E. coli leader peptidase, we have combined site-directed mutagenesis and chemical modification methods to introduce unnatural amino acid side chains at the 145-position. We show that partial activity can be restored to an inactive K145C leader peptidase mutant by reacting it with 2-bromoethylamine.HBr to produce a lysine analog (gamma-thia-lysine) at the 145-position. Modification with the reagents 3-bromopropylamine.HBr and 2-mercaptoethylamine also allowed for partial restoration of activity showing that there is some flexibility in the length requirements of this essential residue.
2.Hydrolysis and rearrangement of phthalamic acid derivatives and assessment of their potential as prodrug forms for amines.
Bundgaard H1, Steffansen B. Acta Pharm Nord. 1990;2(5):333-42.
Although it is well-known that N-substituted phthalamic acid derivatives are readily hydrolyzed in acidic aqueous solution due to intramolecular catalysis by the neighbouring carboxy group, sparse information is available on the degradation behaviour in neutral solutions. A recent publication  has claimed that N-(3-bromopropyl)phthalamic acid is very easily hydrolyzed in mildly alkaline solutions by an intramolecular catalytic effect of the ionized carboxy group. In this study, the degradation behaviour of N-(2-bromoethyl)phthalamic acid (I), N-(3-bromopropyl)phthalamic acid (II) and various other N-alkyl and N-aryl substituted phthalamic acid derivatives were examined with the primary aim of assessing their degradation rate at physiological pH. Whereas the compounds I and II were indeed found to be easily degraded in neutral aqueous solutions, the degradation was not due to hydrolysis of the amide bond as previously claimed but rather to an intramolecular displacement reaction of the bromo group by the amide moiety, as evidenced by HPLC analysis of the rection products.
3.Aldehyde methacrylates derived from hydroxybenzaldehydes.
Antonucci JM. J Dent Res. 1978 Mar;57(3):500-5.
Three crystalline aldehyde methacrylates with low melting points were synthesized from the readily available, isomeric hydroxybenzaldehydes and 2-bromoethyl methacrylate. These monomers can be purified by recrystallization and liquified by admixture in various proportions to obtain polymerizable liquids having workable viscosities at room temperature. These monomers may be used alone or as blends with other methacrylates since they are miscible and copolymerizable with the usual dental monomers. Also, they should be studied with other functional methacrylates designed to promote adhesion via the mineral phase to determine if this synergistic approach can improve the adhesion of dental resins to dentin. These aldehyde methacrylates, their mixtures, polymers and copolymers merit evaluation as adhesion-promoting agents for proteinaceous substrates such as bone and dentin.
4.New arylpiperazine derivatives as antagonists of the human cloned 5-HT(4) receptor isoforms.
Curtet S1, Soulier JL, Zahradnik I, Giner M, Berque-Bestel I, Mialet J, Lezoualc'h F, Donzeau-Gouge P, Sicsic S, Fischmeister R, Langlois M. J Med Chem. 2000 Oct 5;43(20):3761-9.
New derivatives of arylpiperazine 9 were designed from ML 10302, a potent 5-HT(4) receptor agonist in the gastrointestinal system. Compounds were synthesized by condensation of a number of available arylpiperazines or heteroarylpiperazines with 2-bromoethyl 4-amino-5-chloro-2-methoxybenzoate. They were evaluated in binding assays on the recently cloned human 5-HT(4(e)) isoform stably expressed in C6 glial cells with [(3)H]GR 113808 as the radioligand. The affinity values (K(i)) depended upon the substituent on the aromatic ring. A chlorine atom produced a marked drop in activity (K(i) > 100 nM), while a m-methoxy group gave a compound with nanomolar affinity (K(i) = 3 nM). The most potent compounds were the heterocyclic derivatives with pyrimidine, pyrazine, pyridazine, or pyridine moieties (compounds 9r, 9t, 9u, 9x, respectively). K(i) values for 9a and 9r were determined for the 5-HT(4(a)), 5-HT(4(b)), 5-HT(4(c)), and 5-HT(4(d)) receptor isoforms transiently expressed in COS cells.