*3.4. Characterization of Compounds* **1**–**5**

*Bis(3,8*α*-dimethyl-5-methylene-4,4*α*,5,6,7,8,8*α*,9-octahydronaphtho-[2,3-*β*]-furan-2-yl)methane* (**1**), (methylenebiatractylon), white amorphous powder. UV (MeOH): λmax (logε) = 231 (3.95) nm. IR (ART): *V*max = 2926.0, 2849.5, 1641.9, 1440.6, 1378.1, 1231.9, 1250.5, 1136.8, 889.0, 758.5 cm<sup>−</sup>1. 1H-NMR and 13C-NMR data see Table 1. HR-APCI-MS: *m*/*z* = 445.3134 [M + H]<sup>+</sup> (calc'd. for C31H41O2 = 445.3106).

*2,2*- *-(Ethane-1,1-diyl)-bis(3,8*α*-dimethyl-5-methylene-4,4*α*,5,6,7,8,8*α*,9-octahydronaphtho-[2,3-*β*]-furan)* (**2**), (ethylidene-biatractylon), white amorphous powder. UV (MeOH): λmax (logε) = 228 (4.02) nm. IR (ART): *V*max = 2926.0, 2847.7, 1641.9, 1440.6, 1377.3, 1138.7, 889.0, 758.5 cm−1. 1H-NMR and 13C-NMR data see Table 1. HR-APCI-MS: *m*/*z* = 459.3267 [M + H]<sup>+</sup> (calc'd. for C32H43O2 = 459.3262).

*2,2*- *-(furan-2-ylmethylene)-bis(3,8*α*-dimethyl-5-methylene-4,4*α*,5,6,7,8,8*α*,9-octahydronaphtho-[2,3-*β*]-furan)* (**3**) (furan-2-methanetriyl–biatractylon), white amorphous powder. UV (MeOH): λmax (logε) = 229 (4.12) nm. IR (ART): *V*max = 2924.1, 2849.5, 1641.9, 1377.3, 1440.6, 1340.0, 1250.5, 1231.9, 1181.6, 1136.8, 899.0, 762.2, 730.6 cm<sup>−</sup>1. 1H-NMR and 13C-NMR data see Table 1. HR-APCI-MS: *m*/*z* = 511.3221 [M + H]<sup>+</sup> (calc'd. for C35H43O3 = 511.3212).

*(5-(bis(3,8*α*-dimethyl-5-methylene-4,4*α*,5,6,7,8,8*α*,9-octahydronaphtho-[2,3-*β*]-furan-2-yl)methyl)furan-2 yl)methanol* (**4**) (5-furanmethanol-2-methanetriyl-biatractylon), white amorphous powder. UV (MeOH): λmax (logε) = 230 (4.17) nm. IR (ART): *V*max = 2924.1, 2845.8, 1641.9, 1440.6, 1377.3, 1250.5, 1233.7, 1136.8, 1013.8, 889.0, 786.5, 758.5 cm<sup>−</sup>1. 1H-NMR and 13C-NMR data see Table 1. HR-APCI-MS: *m*/*z* = 541.3299 [M + H]<sup>+</sup> (calc'd. for C36H45O4 = 541.3318).

*2,2*- *-((5-((3,8*α*-dimethyl-5-methylene-4,4*α*,5,6,7,8,8*α*,9-octahydronaphtho-[2,3-*β*]-furan-2-yl)methyl)furan-2-yl)methylene)bis(3,8*α*-dimethyl-5-methylene-4,4*α*,5,6,7,8,8*α*,9-octahydronaphtho-[2,3-*β*]-furan)* (**5**) (furan-5-methanediyl-2-methanetriyl-triatractylon), white amorphous powder. UV (MeOH): λmax (logε) 230 (4.30) nm. IR (ART): *V*max = 2953.9, 2924.1, 2853.3, 1459.3, 1377.3, 1272.9, 1136.8, 1123.8, 1073.5, 1015.7, 889.0 cm<sup>−</sup>1. 1H-NMR and 13C-NMR data see Table 1. HR-APCI-MS: *m*/*z* = 739.4719 [M + H]<sup>+</sup> (calc'd. for C51H63O4 = 739.4726).

The NMR, MS, UV, and IR spectra of above five compounds are presented in the Supplementary Materials, which are available free of charge via the internet at https://www.mdpi.com/journal/molecules.
