Cyclic sulfur-containing compounds from Allium fistulosum 'Kujou'.

Sulfur-containing compounds, allicin and ajoene, etc., were isolated from Allium species. In a recent study, some sulfur-containing cyclic compounds were isolated from A. sativum, A. cepa, and A. fistulosum. Four new compounds with multiple rings with methyl disulfide or propyl disulfide at the side chain of the 7-position, kujounins A₃ (1), B₁ (2), B₂ (3) and B₃ (4), and two new thiolane type compounds with methoxy and methyl sulfoxide moiety at the 2- and 5-positions, and allium sulfoxides A₂ (5) and A₃ (6), were isolated from the acetone extract of the fresh white parts of Allium fistulosum 'Kujou' with three known compounds, kujounin A₁ (7) and A₂ (8), and allium sulfoxide A₁ (9). The chemical structures of the new compounds were elucidated on the basis of physicochemical evidence. The kujounins had a rare molecular skeleton, which was tetrahydro-2H-difuro[3,2-b:2',3'-c]furan-5(5aH)-one.