טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentSandlers Yana
SubjectDesign and Synthesis of Mechanism Based Inhibitor of the
Enzyme 3-Deoxy-D-manno-2-octulosonate-8-phosphate
synthase
DepartmentDepartment of Chemistry
Supervisor Professor Timor Baasov


Abstract

 

 

 
    The enzyme 3-deoxy-D-manno-2-octulosonate-8-phosphate (KDO8P) synthase catalyzes the condensation reaction between D-arabinose-5-phosphate (A5P) and  phosphoenolpyruvate (PEP) to form KDO8P and inorganic phosphate. This important enzymatic reaction plays a crucial role in the assembly process of lipopolysaccaride of most Gram-negative bacteria, and therefore is an attractive target for the design of novel antibacterial drugs.Earlier studies have postulated that the KDO8P-synthase-catalyzed reaction proceeds through the mechanism involving the formation of acyclic intermediate 2.

Scheme 1a: Proposed mechanistic pathway for KDO8P-synthase-catalazed reacion


Although this proposal was based  on reasonable chemical grounds, there is no direct evidence for the formation of 2 as a reaction intemediate.Therefore, we designed, structure 5 which is a stable phosphonate analogue of the putative hemiketal intermediate 2

We have developed two alternative synthetic pathways for the preparation of 5. We have succesfully accomplished insertion of the phosphonate group and  have separated and characterized diastreriomes (at C-2) of the phosphonate 13.


The alternative pathway includes synthesis of the ketoester 23.


Compound 23 was then transformed to the diastereomeric mixture of 24, which after several steps of synthesis afforded protected phosphonophosphate 28 as a mixture of diastereomers. Further deprotection steps are needed to complete the synthesis of 5. In summary, although the synthesis of the target compound 5 has not yet been accomplished,we already performed the most important steps for the assembly of 5, including insertion of the phosphate and phosphonate groups. Performance of deprotection steps on 28 will lead to the target compound 5, which is expected to serve as potent inhibitor of the enzyme.