Two new sesquiterpenoids (alpinolide and hanamyol) were isolated from Alpinia japonica (THUNB.) MIQ. and the structures were determined by the spectral, the chemical evidence and X-ray analysis. The chemical transformation of hanalpinol into alpinolide may suggest the biogenesis of furopelargone A and B.
A novel sesquiterpene peroxide, hanalpinol (1a), has been isolated from the rhizomes of Alpinia japonica. Oxidation of 1a with pyridinium chlorochromate gave a crystalline, α, β-unsaturated ketone (2), whose structure was established by means of X-ray analysis. The IR spectrum of 1a revealed the presence of intramolecular hydrogen bonding, and acid treatment of 1a resulted in the formation of furopelargone B (4), which was present naturally in the same plant. This conversion reaction suggests that 4 is biosynthesized from 1a or its analog. Furopelargone A (3) was also isolated.