Abstract
RA-VII analogues fluorinated at each ε-position of Tyr-5 were designed. The synthesis
of these peptide analogues commenced with the preparation of atropisomeric fluorocycloisodityrosines
from protected 3-fluoro-L-tyrosyl-3-boronyl-L-tyrosine mediated by copper(II) acetate
and 4-(dimethylamino)pyridine. After N-methylation, the tetrapeptide segment was coupled
with the N-terminus of each fluorocycloisodityrosine to afford a hexapeptide. After
removal of the C- and N-terminal protecting groups, each peptide was subjected to
macrocyclization to produce an analogue. The analogue with a β-oriented fluorine atom
was equipotent to RA-VII with regard to cytotoxicity toward human mammary carcinoma
MCF-7 cells, and showed 2.1-fold and 1.4-fold lower cytotoxicities than RA-VII toward
human promyelocytic leukemia HL-60 and human colorectal cancer HCT-116 cells, respectively,
whereas the analogue with an α-oriented fluorine atom showed 7.7-fold, 6.0-fold, and
14-fold lower cytotoxicities than RA-VII toward those cells, respectively.
Key words
RA-VII analogues - peptides - macrocyclic peptides - medicinal chemistry - cytotoxicity
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Rubia cordifolia