Stereochemistry of C-6 nucleophilic displacements on 1,1-difluorocyclopropyldibenzosuberanyl substrates. An improved synthesis of multidrug resistance modulator LY335979 trihydrochloride

J Org Chem. 2004 Oct 29;69(22):7653-60. doi: 10.1021/jo049051v.

Abstract

Studies of the displacement chemistry of 1,1-difluorocyclopropyldibenzosuberanyl alcohol 4 and its activated bromide derivative 6 have led to an improved approach to anti-2, a key precursor to LY335979 3HCl (1). Bromination of either syn-4 or anti-4 gave anti-oriented 6, indicating thermodynamically controlled product stereochemistry via a stabilized 1,1-difluorohomotropylium ion intermediate. Reaction of 6 with piperazine proceeded irreversibly to provide an isomeric mixture of piperazine products, with the syn:anti product ratio increased by solvent effects. Reaction of 6 with pyridine and pyrazine, on the other hand, gave anti-pyridinium and pyrazinium salts, respectively, apparently via equilibration of initially formed syn products. Reduction of pyrazinium salt 11 with lithium borohydride/TFA provided anti-2 unaccompanied by its syn isomer. A practical and expeditious approach to 1 was derived from these new results.

MeSH terms

  • Combinatorial Chemistry Techniques*
  • Dibenzocycloheptenes / chemical synthesis*
  • Dibenzocycloheptenes / pharmacology
  • Drug Resistance, Multiple
  • Hydrocarbons, Fluorinated / chemistry*
  • Hydroxamic Acids / chemistry
  • Magnetic Resonance Spectroscopy
  • Molecular Structure
  • Quinolines / chemical synthesis*
  • Quinolines / pharmacology
  • Stereoisomerism

Substances

  • Dibenzocycloheptenes
  • Hydrocarbons, Fluorinated
  • Hydroxamic Acids
  • Quinolines
  • zosuquidar trihydrochloride