Systematic Synthesis of Inhibitors of the Two First Enzymes of the Bacterial Heptose Biosynthetic Pathway: Towards Antivirulence Molecules Targeting Lipopolysaccharide Biosynthesis

Abstract

L-Heptoses (L-glycero-D-manno-heptopyranoses) are constituents of the inner core of lipolysaccharide (LPS), a molecule playing key roles in the mortality of many infectious diseases as well as in the virulence of many human pathogens. The inhibition of the first enzymes of the bacterial heptose biosynthetic pathway is an almost unexplored field to date although it appears to be a very novel way for the development of antivirulence drugs. We report the synthesis of a series of D-glycero-D-manno-heptopyranose 7-phosphate (H7P) analogues and their inhibition properties against the isomerase GmhA and the the kinase HldE, the two first enzymes of the bacterial heptose biosynthetic pathway. The heptose structures have been modified at the 1-, 2-, 6- and 7-positions to probe the importance of the key structural features of H7P that allow a tight binding to the target enzymes; H7P being the product of GmhA and the substrate of HldE, the second objective was to find structures that could simultaneously inhibit both enzymes. We found that GmhA and HldE were extremely sensitive to structural modifications at the 6- and 7- positions of the heptose scaffold. To our surprise, the epimeric analogue of H7P displaying a D-glucopyranose configuration was found to be the best inhibitor of both enzymes but also the only molecule of this series that could inhibit GmhA (IC(50)=34 μM) and HldE (IC(50)=9.4 μM) in the low micromolar range. Noteworthy, this study describes the first inhibitors of GmhA ever reported, and paves the way to the design of a second generation of molecules targeting the bacterial virulence.

Debenzylative Cycloetherification: An Overlooked Key Strategy for Complex Tetrahydrofuran Synthesis

“…In 2013, Vincent and Tikad explored the DBCE reaction to perform the synthesis of conformationally constrained methyl 3,6‐anhydro‐ l ‐glycero‐α‐ d ‐manno‐heptopyranoside 7‐phosphate 106 , an analogue of methyl d ‐glycero‐ d ‐gluco‐heptopyranose 7‐phosphate 107 , which is the best inhibitor of both enzymes GmhA (IC 50 =34 μ m ) and HldE (IC 50 =9.4 μ m ), the two first enzymes of the bacterial heptose biosynthetic pathway (Scheme ) . Based on the debenzylative cyclization induced by DAST as a key step in this strategy, the target 3,6‐anhydroheptosides 103 – 105 were achieved after a few hours in good to excellent yields, whatever the nature of starting l ‐heptoside used ( 100 – 102 ; Scheme ).…”

The Inhibition of Liposaccharide Heptosyltransferase WaaC with Multivalent Glycosylated Fullerenes: A New Mode of Glycosyltransferase Inhibition

“…We found that the scaling-up of the latter step was highly problematic. Actually, we have recently reported a modification of the Fleming-Tamao procedure allowing the synthesis of l,d-heptoside 5 on a multigram scale, [26] this compound was thus selected as the starting material for the preparation of alkynylated heptoses 9 and 10 (Scheme 1).…”

“…The copper-catalyzed cycloaddition of azide 11 with alkyne 9 gave model compound A in 65 % yield. The synthesis of the targeted octoside building block 14 was performed from the known molecule 12 [26] (Scheme 2). Per- The preparation of fullerene sugar balls C 60 A C H T U N G T R E N N U N G (A-F) 12 is depicted in Scheme 3 and Scheme 4.…”

“…Compounds C 60 (Ph) 12 , [28] 1, [38] 2, [39] 3, [7] 4, [26] 5, [26] 11, [7] 12, [26] and 15 [27] were prepared according to previously reported procedures, whereas the preparation of compounds 6, 7, 8, 9, 10, 13, and 14 is given in the Supporting Information.…”

Environmentally friendly approaches to the synthesis of new antibiotics from sugars

“…Therefore, the search for inhibitors of LPS biosynthesis has been a valuable strategy in antibacterial drug design. Syntheses of inhibitors of the biosynthetic pathways leading to KDO [17], to lipid A [18], and more recently, to L-glycero-D-manno-heptose [19] have been explored.…”