A compound of the formula (I): wherein each symbol is as defined in the DESCRIPTION, or a pharmaceutically acceptable salt thereof has a superior Notch signal transduction inhibitory action, and is useful for preventing or treating various diseases involving Notch signal transduction.
Synthesis of Optically Active Phthaloyl <scp>d</scp>-Aminooxy Acids from <scp>l</scp>-Amino Acids or <scp>l</scp>-Hydroxy Acids as Building Blocks for the Preparation of Aminooxy Peptides