“…Different stereoisomers of phomalactone ( F ) were isolated and reported previously from various sources [ 15 , 16 , 17 , 18 ], and some papers did not specify the absolute configuration [ 19 , 20 ], while others assigned the (5 R ,6 R ) absolute configuration to the large positive specific rotation [ 21 ], which was opposite to previous studies [ 15 , 16 , 17 , 18 , 22 ]. In order to determine the absolute configuration of phomalactone independently and unambiguously, we performed TDDFT-ECD, TDDFT-OR, and DFT-VCD studies, which consistently confirmed the (+)- cis -(5 S ,6 S ) absolute configuration (see Supplementary Materials ) [ 23 , 24 ].…”