Diastereoselectivity control of the radical carboazidation of substituted methylenecyclohexanes.

A systematic study of the diastereoselectivity of the radical carboazidation of methylenecyclohexane derivatives is presented. Several substitution patterns leading to a high level of stereocontrol have been identified. Axial attack is the preferred reaction pathway for cyclohexyl radicals, and excellent stereoselectivities can be obtained by introducing an axial substitutent at position 2. In this case, a second equatorial substituent at position 2 may be tolerated without a large detrimental effect on the diastereoselectivity. Finally, a high level of equatorial attack is observed with a very bulky substituent at position 2.

A rapid synthesis of hexofuranose-like iminosugars using ring-closing metathesis.

Two new 1-N-iminosugars have been prepared as hexofuranose analogues in an efficient manner by an RCM-based route. Both 3,4-disubstituted pyrrolidines display moderate inhibitory activity against Mycobacterium smegmatis galactan biosynthesis. [structure: see text]

Identification of Novel Inhibitors of UDP-Galactopyranose Mutase by Structure-Based Virtual Screening.

UDP-galactopyranose mutase (UGM) is a flavo-enzyme involved in the bacterial cell wall biosynthesis. UGM catalyzes the reversible isomerization of UDP-galactopyranose (UDP-Galp) to UDP-galactofuranose (UDP-Galf). UDP-Galf is the activated precursor of galactofuranose (Galf) residues that are essential components of the cell wall of certain pathogenic bacteria such as Klebsiella pneumoniae and Mycobacterium tuberculosis. Neither UGM nor Galf residues are found in humans, making Galf biosynthesis a potential drug target for developing antibacterial agents. We report the identification of novel inhibitors of UGM by in silico docking of the LeadQuest compound database against UGM from Escherichia coli. The 13 most promising inhibitors were then evaluated against K. pneumonia and M. tuberculosis UGMs by enzyme inhibition studies. Two inhibitors were identified with IC50 values of ∼1 µM and subsequently these compounds were docked into the recently solved X-ray structure of Deinococcus radiodurans UGM. The structure-activity relationships of the initial 13 compounds evaluated as inhibitors are discussed.

Synthesis and biological evaluation of new inhibitors of UDP-Galf transferase--a key enzyme in M. tuberculosis cell wall biosynthesis.

Two iminosugars have been designed and synthesized as potential inhibitors of UDP-Galf transferase, an enzyme involved in Mycobacterium tuberculosis cell wall biosynthesis. The design is based on a proposed model of the transition state for the transferase reaction. One of the two racemic compounds is the first reported inhibitor of the target enzyme from M. smegmatis.