Synthesis of N-epsilon-lithocholyl-L-lysine, a component of tissue-bound lithocholic acid, via lithocholyl-N-hydroxysuccinimide.

N-epsilon-lithocholyl-l-lysine is a lithocholic acid modified lysine residue found in proteins from tissues. This paper describes the synthesis of this compound as well as that of the isomeric N-alpha-lithocholyl-l-lysine and the di-substituted N-alpha-epsilon-bis-lithocholyl-l-lysine. The procedure involves the initial coupling of lithocholyl-N-hydroxysuccinimide to the appropriate N-alpha- or N-epsilon-CBZ (carbobenzloxy) protected lysine derivative followed by hydrogenolysis with palladium black of the CBZ group using formic acid as the hydrogen donor.