- no.22, pp.235-242, 1979-09-20
From a higher boiling fraction (Bp>100℃/8 Torr) of peppermint oil (Mentha piperia L.) was isolated a white crystalline (mp 59-61℃, 300 mg from 80 g of the fraction) having a molecular formula of C_<15>H_<24>S. The structure of the crystalline was unequivocally determined by X-ray crystallographic analysis and we named it mintsulfide (1)(abbreviated as MS). Ultraviolet irradiation (Pyrex filter) of (-)-germacrene D (2)(abbreviated as GD), one of the major components of the oil, in the presence of sulfur powder afforded the mintsulfide (1), thus demonstrating the absolute configuration of MS. The mintsulfide was converted into the isomer (4). Both 1 and 4 were oxidized to give the products (5〜10), which showed the chemical shifts in the NMR spectra as summarized in table 1 and 2. Table 3 indicates the results of photochemical conversion of GD (2), giving MS (1) and/or β-bourbonene (3) under the various conditions. The evidence in table 3 suggests that activated sulfur (sulfur atom ?) is generated first under the Pyrex filtered irradiation. The activated sulfur reacts with GD, leading the formation of MS (1). This novel photoreaction is substrate specific since presence of caryophyllene (12) or β-bourbonene (3) affects no influence. The preliminary experiments revealed that myrcene (13) and tenmembered diene (14) also react with the photo-activated sulfur.