Development of Carbohydrate-based Therapeutic and Anti-infective Compounds

My research group has developed expedient methodologies for the preparation of a library of structurally diverse unusual sugars. These unusual sugars can be incorporated stereoselectively onto selective molecules, generating a library of glycosylated compounds with immense biological interest: a strategy, which we called, glycodiversification. Using glycodiversification strategy, my group can quickly evaluate the properties of sugar-containing molecules, leading to various applications in areas including chemistry, biology, medicinal chemistry, and pharmacy. Several distinct but cooperative projects are being conducted:

Project 1: Development of Aminoglycoside Antibiotics

Project 2: Antiviral Research

Project 3: Development of Novel Antitubercular Agents

Project 4: Development of Technologies for Complex Carbohydrate Synthesis

Project 5: Development of Carbohydrate Conjugates

Project 6: Development of Novel Antifungal Agents

Research Introduction

             The principle goal for this project is to develop broad spectrum aminoglycoside antibiotics against diverse drug resistant bacteria. The practical applications of this project will be in the areas of infectious disease treatment and anti-bioterrorism. Two different branches of aminoglycosides, pyranmycins and kanamycin B analogs were developed. In collaboration with Dr. Czyryca, we also employ molecular modeling for the rationale-based designs of new pyranmycins and kanamycin B analogs.

A. Pyranmycins Project

Minimum Inhibitory Concentration (mM) of Pyranmycins

Summary:

(a)       Pyranmycins have comparable antibacterial activity to neomycin. However, pyranmycins have much-improved stability in acidic media.

(b)      Pyranmycins have broad spectrum activity like neomycin.

(c)       New members of pyranmycins have been constructed, and are found to be active against aminoglycoside resistant bacteria. I have submitted the invention disclosure form for patent application.

Related Publications in Pyranmycins Library

(1)        Wang, J.; Li, J.; Tuttle, D.; Takemoto, J.; Chang, C.-W. T. " The synthesis of L-aminosugar and the studies of L-pyranoses on the ring III of pyranmycins." Org. Lett. 2002, 4, 3997-4000.

(2)        Chang, C.-W. T.; Hui, Y.; Elchert, B.; Wang, J.; Li, J.; Rai, R. "Pyranmycins, a novel class of aminoglycosides with improved acid stability: the SAR of D-pyranoses on ring III of pyranmycin." Org. Lett. 2002, 4, 4603-4606.

(3)        Li, J.; Wang, J.; Hui, Y.; Chang, C.-W. T. "Exploring the Optimal Site for Modification of Pyranmycin with the Extended Arm Approach." Org. Lett. 2003, 5, 431-434.

(4)        Elchert, B.; Li, J.; Wang, J.; Hui, Y.; Rai, R.; Ptak, R.; Ward, P.; Takemoto, J. Y.; Bensaci, M.; Chang, C.-W. T. "Application of the Synthetic Aminosugars for Glycodiversification: Synthesis and Antimicrobial Studies of Pyranmycin." J. Org. Chem., 2004, 69, 1513-1523.

(5)        Wang, J.; Li, L.; Czyryca, P. G.; Chang, H.; Kao, J.; Chang, C.-W. T. “Synthesis of an Unusual Branched-chain Sugar, 5-C-methyl-L-idopyranose for SAR Studies of Pyranmycins: Implications for the Future Design of Aminoglycoside Antibiotics.” Bioorg. Med. Chem. Lett. 2004, 14, 4389-4393.

(6)        Rai, R.; Chang, H.; Chen, H.-N.; Chang, C.-W. T. “Novel Method for the Synthesis of 3’,4’-Dideoxygenated Pyranmycin and Kanamycin Compounds, and Studies of Their Antibacterial Activity against Aminoglycoside Resistant Bacteria.” J. Carbohydr. Chem. 2005, 24, 131-143.

(7)        Li, J.; Chen, H.-N.; Chang, H.; Wang, J.; Chang, C.-W. T. “Tuning the Regioselectivity of Staudinger Reaction for the Facile Synthesis of Kanamycin and Neomycin Class Antibiotics with N-1 Modification.” Org. Lett. 2005, .7, 3061-3064.

(8)        Rai, R.; Chen, H.;  Czyryca, P. G.; Li, J.; Chang, C.-W. T. “Design and Synthesis of Pyrankacin: A Pyranmycin Class Broad Spectrum Aminoglycoside Antibiotic.” Org. Lett. 2006, 8, 887-889.

B. Kanamycin B Analog Project

Minimum Inhibitory Concentration (mM) of Kanamycin B Analogs

Binding of JL005 toward 16S rRNA from Molecular Modeling

C. Designs against Aminoglycoside Resistant Bacteria

Overexpression of aminoglycoside modifying enzymes (AME) from resistant bacteria is the most commonly encountered mode of resistance. Various aminoglycoside modifying enzymes have been identified that catalyze a wide range of modifications including acetylation, phosphorylation, and adenylation, which prevent the modified aminoglycosides from binding to the targeted site of rRNA and, thus, enable the bacteria to acquire resistance. These enzymes are grouped as aminoglycoside phosphotransferases (APHs), aminoglycoside acetyltransferases (AACs), and aminoglycoside nucleotidyltransferases (ANTs). However, more than fifty different isoforms of these enzymes have been clinically isolated with subtle to significant differences in their capability of modifying various aminoglycosides.

C.1. 3’,4’-Dideoxygenation

One of the most prevalent modifying enzymes is APH(3’) that catalyzes phosphorylation at the 3’-OH of both neomycin and kanamycin classes of aminoglycosides rendering the phosphorylated adduct incapable of binding toward the ribosomal target. Dideoxygenation at 3’ and 4’ positions has been proved to be effective against APH(3’) as reported by Umezawa and others. The concept has led to the syntheses and discovery of tobramycin, arbekacin and other similar aminoglycosides.

Our group has completed the synthesis of RR501 and RT501 bearing 3’,4’-dideoxygenation. As expected, both RR501 and RT501 are active against resistant bacteria equipped with APH(3’). They are, however, less active against bacteria equipped with AAC6'/APH2".

Unit: μg/mL

C.2. N-1 Modification

Attaching functionalities at the N-1 position of the 2-deoxystreptamine among kanamycin or neomycin class antibiotics, is one of the other most effective methods of reviving the activity against aminoglycoside resistant bacteria. This strategy has led to the development of semi-synthetic amikacin that has an (S)-4-amino-2-hydroxybutyryl (AHB) group at N-1 position.

Our group has successfully increased the reactivity of N-1 azido group by introducing di-(4-chlorobenzoyl) at O-5 and O-6 positions leading to the synthesis of several aminoglycosides bearing N-1 AHB group.

Unit: μg/mL

C.3. Aminoglycosides having both 3’,4’-dideoxygenation and N-1 modification