Spiro-isoxazolines from the flowers of Xanthoceras sorbifolia

Four tyrosine-derived spiro-isoxazoline analogues, including two new ones (3–4), were isolated from the flowers of Xanthoceras sorbifolia Bunge. The planar structures and the conformations were established by the analyses of the 1D and 2D NMR spectroscopic data, and the absolute configuration of compound 4 was determined via ECD calculation by time-dependent density functional theory (TDDFT). The biosynthetic pathway involving oxidative...