Characterization of D-boroala as a novel Broad-spectrum antibacterial agent targeting D-Ala-D-Ala ligase & designer linkers : model reactions and linear free energy relationships in the reactivity and design of solid-phase linkers

Bacterial infections were the major cause of death and morbidity prior to the development of modern antibiotics, and the increasing resistance of pathogenic bacteria to commonly used antibacterial agents is a major public health concern. During our efforts to develop transition-state analog inhibitors for bacterial cell wall–synthesizing enzymes, we observed that D-boroAlanine (D-Ala with the -COOH group replaced with a -B(OH)2 group) had effective antibacterial activity. In the first part of this dissertation, we describe the antibacterial properties of D-boroAla, structure–activity correlation among several D-boroAla homologs, and determination of the biochemical mechanism for D-boroAla’s antibacterial activity. This study demonstrates that D-boroAla has broad-spectrum antibacterial activity and targets D-Ala-D-Ala ligase (DDL) in the alanine branch of bacterial cell wall biosynthesis. Vancomycin exerts its antibacterial effect by binding to the D-Ala-D-Ala termini of pentapeptide peptidoglycan precursors, thereby interfering with the last steps of bacterial cell wall biosynthesis. In the most clinically common resistance mechanisms in VRE, the terminal D-Ala-D-Ala moiety of peptidoglycan precursors is replaced by D-Ala-D-Lac. The middle section of the dissertation deals with developing an LC-MS/MS assay for detection and quantitation of D-Ala-D-Lac, the key intermediate for most types of vancomycin resistance. This assay was validated and then used to demonstrate the effect of vancomycin induction on alanine branch metabolites – including D-Ala-D-Lac, in VRE. Considerable research has been done on the synthesis of peptides and peptide mimetics using classical solid-phase peptide synthesis (SPPS) in the classical C-to-N direction. However, this strategy is not generally useful for preparing C-terminally modified peptide derivatives, which are of high interest as bioactive agents and drugs. SPPS in the N-to-C direction inverse SPPS (ISPPS) would provide the synthetically versatile C-terminal carboxyl group for further elaboration. Prior studies in our laboratory established the feasibility of performing ISPPS using readily available amino acid OtBu esters. In the last section of this dissertation, described efforts to develop a backbone amide attachment linkers with the appropriate chemical stability for ISPPS i.e. stable to 25% TFA/DCM treatment and cleavable with 5% HBr/TFA. Candidate linkers were then loaded onto aminomythylated polystyrene resin to demonstrate an effective method for ISPPS using amino acid t-butyl esters. Chemical sensitivity to different capping groups on sensitivity to cleavage was demonstrated and several tripeptides were synthesized using this approach

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Pharmaceutical Sciences (UMKC)

Grantor

University of Missouri--Kansas City

Year dc:date.issued

2014

Author dc:creator

• Putty, Sandeep

Advisor dc:contributor.advisor

• Gutheil, William G. (William Glenn)

Handle dc:identifier.uri

http://hdl.handle.net/10355/43507

OAI identifier oai:identifier

oai:mospace.umsystem.edu:10355/43507