Synthesis, stereochemistry and SAR of a series of minodronate analogues as RGGT inhibitors

Eur J Med Chem. 2011 Oct;46(10):4820-6. doi: 10.1016/j.ejmech.2011.04.063. Epub 2011 May 7.

Abstract

Phosphonocarboxylate (PC) analogues of bisphosphonates are of interest due to their selective inhibition of a key enzyme in the mevalonate pathway, Rab geranylgeranyl transferase (RGGT). The dextrarotatory enantiomer of 2-hydroxy-3-(imidazo[1,2-a]pyridin-3-yl)-2-phosphonopropanoic acid (3-IPEHPC, 1) is the most potent PC-type RGGT inhibitor thus far identified. The absolute configuration of (+)-1 in the active site complex has remained unknown due to difficulties in obtaining RGGT inhibitor complex crystals suitable for X-ray diffraction analysis. However, we have now succeeded in crystallizing (-)-1 and here report its absolute configuration (AC) obtained by X-ray crystallography, thus also defining the AC of (+)-1. An Autodock Vina 1.1 computer modeling study of (+)-1 in the active site of modified RGGT binding GGPP (3DSV) identifies stereochemistry-dependent interactions that could account for the potency of (+)-1 and supports the hypothesis that this type of inhibitor binds at the TAG tunnel, inhibiting the second geranylgeranylation step. We also report a convenient (31)P NMR method to determine enantiomeric excess of 1 and its pyridyl analogue 2, using α- and β-cyclodextrins as chiral solvating agents, and describe the synthesis of a small series of 1 α-X (X = H, F, Cl, Br; 7a-d) analogues to assess the contribution of the α-OH group to activity at enzyme and cellular levels. The IC(50) of 1 was 5-10× lower than 7a-d, and the LED for inhibition of Rab11 prenylation in vitro was 2-8× lower than for 7a-d. However, in a viability reduction assay with J774 cells, 1 and 7b had similar IC(50) values, ~10× lower than those of 7a and 7c-d.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkyl and Aryl Transferases / antagonists & inhibitors*
  • Alkyl and Aryl Transferases / chemistry
  • Alkyl and Aryl Transferases / metabolism*
  • Animals
  • Cell Line
  • Cell Survival / drug effects
  • Crystallography, X-Ray
  • Diphosphonates / chemistry*
  • Diphosphonates / pharmacology*
  • Enzyme Inhibitors / chemistry*
  • Enzyme Inhibitors / pharmacology*
  • Humans
  • Imidazoles / chemistry*
  • Imidazoles / pharmacology*
  • Models, Molecular
  • Protein Binding
  • Stereoisomerism

Substances

  • Diphosphonates
  • Enzyme Inhibitors
  • Imidazoles
  • YM 529
  • Alkyl and Aryl Transferases
  • Rab geranylgeranyltransferase