N-(tert-Butoxycarbonyl)-L-leucine N′-methoxy-N′-methylamide is a Boc-protected L-leucine derivative with a C-terminal Weinreb amide (N-methoxy-N-methylamide) functionality. This specialty chemical serves as a key intermediate in organic and peptide synthesis, particularly for the preparation of peptidyl ketones. The Weinreb amide reacts selectively with Grignard reagents, organolithium compounds, or other organometallics to form stable ketones without over-addition, enabling the synthesis of C-terminally ketone-modified peptides, protease inhibitors, and complex biomolecules. The Boc group provides orthogonal N-protection, removable under mild acidic conditions. It is valuable in solution-phase peptide synthesis, medicinal chemistry, and biochemistry for constructing molecules with precise structural modifications and biological activity.