Synthesis of Quaternary α‑Methyl α‑Amino Acids by Asymmetric Alkylation of Pseudoephenamine Alaninamide Pivaldimine

The utility of pseudoephenamine as a chiral auxiliary for the alkylative construction of quaternary α-methyl α-amino acids is demonstrated. The method is notable for the high diastereoselectivities of the alkylation reactions, for its versatility with respect to electrophilic substrate partners, and for its mild hydrolysis conditions, which provide α-amino acids without salt contaminants. Alternatively, α-amino esters can be obtained by direct alcoholysis

Unraveling the Metabolic Pathway in <i>Leucosceptrum canum</i> by Isolation of New Defensive Leucosceptroid Degradation Products and Biomimetic Model Synthesis

Seven new leucosceptroid degradation products possessing a C₂₀, C₂₁, or C₂₅ framework, norleucosceptroids D–H (<b>1</b>–<b>5</b>), leucosceptroids P (<b>6</b>), and Q (<b>7</b>), have been isolated from <i>Leucosceptrum canum</i>. Their structures were determined by comprehensive NMR, MS, and single-crystal X-ray diffraction analyses. Discovery of these key intermediates, together with the biomimetic oxidation of a model system, supports the hypothesis that two biosynthetic pathways are operative. Antifeedant activity was observed for compounds <b>1</b>–<b>3</b>