Details on the X-ray crystal-structure determination and the crystallographic data of compounds 13, 14, 15b, 17a, 17b, 17c can be found in the Supplementary information and supplementary crystallographic data was deposited at CCDC (see Data availability). package following the DP4+ protocol developed by Grimblat, Zanardi and Sarotti. For simplification purposes the rhamnose-dichlorohomoorsellinate moiety was substituted for a methyl group. For S-OP1118 (18e-C( )) the calculations were performed for the full molecule, and the simplified variant (rhamnose-dichlorohomoorsellinate replaced by methyl)