Tautomeric phenomenon of a novel potent immunosuppressant (FK506) in solution. I. Isolation and structure determination of tautomeric compounds

J Antibiot (Tokyo). 1993 Jul;46(7):1149-55. doi: 10.7164/antibiotics.46.1149.


Tautomeric phenomenon was observed in the HPLC chromatogram obtained from a novel potent immunosuppressant, FK506, in ethanol solution. Two tautomeric compounds derived from FK506 were isolated and purified by HPLC. Their structures were elucidated by spectral analyses. The mechanisms for this tautomerization were also established based on the results of structure analysis.

MeSH terms

  • Isomerism
  • Magnetic Resonance Spectroscopy
  • Spectrometry, Mass, Fast Atom Bombardment
  • Tacrolimus / chemistry*
  • Tacrolimus / isolation & purification*


  • Tacrolimus