On Constituents of Caper-spurge Seed (Lathyridis Seed). I. Isolation and Reactions of Epoxylathyrol

Abstract

Several chemical reactions of epoxylathyrol^{3, 4)} (I) were investigated. Catalytic hydrogenation of I gave dihydro I compound, mp 65-68°. Treatment of I with perbenzoic acid gave an epoxy derivative (III), mp 198-200°. Mild alkaline hydrolysis of I yielded a triol, mp 207-209°, C₂₀H₃₀O₅·H₂O, which readily underwent addition with diazomethane to give a pyrazole derivative, mp 100-102°, C₂₁H₃₂O₅N₂·H₂O. Treatment of I with oxalic acid in glacial acetic acid gave a product (IX), mp 207-209°, C₃₃H₄₂O₁₀·H₂O, which exhibited a free hydroxyl absorption at 3450 cm^-1 and lost the conjugated carbonyl group in its infrared spectrum. In the nuclear magnetic resonance spectrum of IX, a methyl group attached to the double bond and the olefinic proton disappeared, and three acetyl groups appeared at δ1.99, 2.04, and 2.21, indicating that one new acetyl group was formed. The methine carrying the new acetyl group, appeared as a doublet at δ4.62 (J=8.0 Hz), indicating a partial structure of [chemical formula]. The spectral properties could be explained with structure IX. This acid-catalyzed transannular cyclization would be initiated by a nucleophilic attack to yield an intermediate (IX-A), which would undergo cleavage of the epoxy ring (IX-B) followed by transannular addition to give compound IX. On the other hand, treatment of I with hydrogen halides in tetrahydrofuran gave the corresponding halides, C₃₂H₄₁O₈Cl (VII), mp 219-221°, C₃₂H₄₁O₈Br (VIII), mp 175-178°, whose epoxy ring would be opened and hydrogen halide added to it.